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and similarly for temperature () and pressure (), where the primed quantities denote fluctuations superposed to the mean. This decomposition of a flow variable into a mean value and a turbulent fluctuation was originally proposed by Osborne Reynolds in 1895, and is considered to be the beginning of the systematic mathematical analysis of turbulent flow, as a sub-field of fluid dynamics. While the mean values are taken as predictable variables determined by dynamics laws, the turbulent fluctuations are regarded as stochastic variables.
The heat flux and momentum transfer (represented by the shear stress ) in the direction normal to the flow for a given time are
where is the heat capacity at constant pressure, is the density of the fluid, is the coefficient of turbulent viscosity and is the turbulent thermal conductivity.
Kolmogorov's theory of 1941
Richardson's notion of turbulence was that a turbulent flow is composed by "eddies" of different sizes. The sizes define a characteristic length scale for the eddies, which are also characterized by flow velocity scales and time scales (turnover time) dependent on the length scale. The large eddies are unstable and eventually break up originating smaller eddies, and the kinetic energy of the initial large eddy is divided into the smaller eddies that stemmed from it. These smaller eddies undergo the same process, giving rise to even smaller eddies which inherit the energy of their predecessor eddy, and so on. In this way, the energy is passed down from the large scales of the motion to smaller scales until reaching a sufficiently small length scale such that the viscosity of the fluid can effectively dissipate the kinetic energy into internal energy.
In his original theory of 1941, Kolmogorov postulated that for very high Reynolds numbers, the small-scale turbulent motions are statistically isotropic (i.e. no preferential spatial direction could be discerned). In general, the large scales of a flow are not isotropic, since they are determined by the particular geometrical features of the boundaries (the size characterizing the large scales will be denoted as ). Kolmogorov's idea was that in the Richardson's energy cascade this geometrical and directional information is lost, while the scale is reduced, so that the statistics of the small scales has a universal character: they are the same for all turbulent flows when the Reynolds number is sufficiently high. | Turbulence | Wikipedia | 483 | 154664 | https://en.wikipedia.org/wiki/Turbulence | Physical sciences | Fluid mechanics | null |
Thus, Kolmogorov introduced a second hypothesis: for very high Reynolds numbers the statistics of small scales are universally and uniquely determined by the kinematic viscosity and the rate of energy dissipation . With only these two parameters, the unique length that can be formed by dimensional analysis is
This is today known as the Kolmogorov length scale (see Kolmogorov microscales).
A turbulent flow is characterized by a hierarchy of scales through which the energy cascade takes place. Dissipation of kinetic energy takes place at scales of the order of Kolmogorov length , while the input of energy into the cascade comes from the decay of the large scales, of order . These two scales at the extremes of the cascade can differ by several orders of magnitude at high Reynolds numbers. In between there is a range of scales (each one with its own characteristic length ) that has formed at the expense of the energy of the large ones. These scales are very large compared with the Kolmogorov length, but still very small compared with the large scale of the flow (i.e. ). Since eddies in this range are much larger than the dissipative eddies that exist at Kolmogorov scales, kinetic energy is essentially not dissipated in this range, and it is merely transferred to smaller scales until viscous effects become important as the order of the Kolmogorov scale is approached. Within this range inertial effects are still much larger than viscous effects, and it is possible to assume that viscosity does not play a role in their internal dynamics (for this reason this range is called "inertial range").
Hence, a third hypothesis of Kolmogorov was that at very high Reynolds number the statistics of scales in the range are universally and uniquely determined by the scale and the rate of energy dissipation .
The way in which the kinetic energy is distributed over the multiplicity of scales is a fundamental characterization of a turbulent flow. For homogeneous turbulence (i.e., statistically invariant under translations of the reference frame) this is usually done by means of the energy spectrum function , where is the modulus of the wavevector corresponding to some harmonics in a Fourier representation of the flow velocity field :
where is the Fourier transform of the flow velocity field. Thus, represents the contribution to the kinetic energy from all the Fourier modes with , and therefore, | Turbulence | Wikipedia | 494 | 154664 | https://en.wikipedia.org/wiki/Turbulence | Physical sciences | Fluid mechanics | null |
where is the mean turbulent kinetic energy of the flow. The wavenumber corresponding to length scale is . Therefore, by dimensional analysis, the only possible form for the energy spectrum function according with the third Kolmogorov's hypothesis is
where would be a universal constant. This is one of the most famous results of Kolmogorov 1941 theory, describing transport of energy through scale space without any loss or gain. The Kolmogorov five-thirds law was first observed in a tidal channel, and considerable experimental evidence has since accumulated that supports it.
Outside of the inertial area, one can find the formula below :
In spite of this success, Kolmogorov theory is at present under revision. This theory implicitly assumes that the turbulence is statistically self-similar at different scales. This essentially means that the statistics are scale-invariant and non-intermittent in the inertial range. A usual way of studying turbulent flow velocity fields is by means of flow velocity increments:
that is, the difference in flow velocity between points separated by a vector (since the turbulence is assumed isotropic, the flow velocity increment depends only on the modulus of ). Flow velocity increments are useful because they emphasize the effects of scales of the order of the separation when statistics are computed. The statistical scale-invariance without intermittency implies that the scaling of flow velocity increments should occur with a unique scaling exponent , so that when is scaled by a factor ,
should have the same statistical distribution as
with independent of the scale . From this fact, and other results of Kolmogorov 1941 theory, it follows that the statistical moments of the flow velocity increments (known as structure functions in turbulence) should scale as
where the brackets denote the statistical average, and the would be universal constants.
There is considerable evidence that turbulent flows deviate from this behavior. The scaling exponents deviate from the value predicted by the theory, becoming a non-linear function of the order of the structure function. The universality of the constants have also been questioned. For low orders the discrepancy with the Kolmogorov value is very small, which explain the success of Kolmogorov theory in regards to low order statistical moments. In particular, it can be shown that when the energy spectrum follows a power law
with , the second order structure function has also a power law, with the form | Turbulence | Wikipedia | 497 | 154664 | https://en.wikipedia.org/wiki/Turbulence | Physical sciences | Fluid mechanics | null |
Since the experimental values obtained for the second order structure function only deviate slightly from the value predicted by Kolmogorov theory, the value for is very near to (differences are about 2%). Thus the "Kolmogorov − spectrum" is generally observed in turbulence. However, for high order structure functions, the difference with the Kolmogorov scaling is significant, and the breakdown of the statistical self-similarity is clear. This behavior, and the lack of universality of the constants, are related with the phenomenon of intermittency in turbulence and can be related to the non-trivial scaling behavior of the dissipation rate averaged over scale . This is an important area of research in this field, and a major goal of the modern theory of turbulence is to understand what is universal in the inertial range, and how to deduce intermittency properties from the Navier-Stokes equations, i.e. from first principles. | Turbulence | Wikipedia | 198 | 154664 | https://en.wikipedia.org/wiki/Turbulence | Physical sciences | Fluid mechanics | null |
In probability and statistics, a probability mass function (sometimes called probability function or frequency function) is a function that gives the probability that a discrete random variable is exactly equal to some value. Sometimes it is also known as the discrete probability density function. The probability mass function is often the primary means of defining a discrete probability distribution, and such functions exist for either scalar or multivariate random variables whose domain is discrete.
A probability mass function differs from a probability density function (PDF) in that the latter is associated with continuous rather than discrete random variables. A PDF must be integrated over an interval to yield a probability.
The value of the random variable having the largest probability mass is called the mode.
Formal definition
Probability mass function is the probability distribution of a discrete random variable, and provides the possible values and their associated probabilities. It is the function defined by
for , where is a probability measure. can also be simplified as .
The probabilities associated with all (hypothetical) values must be non-negative and sum up to 1,
and
Thinking of probability as mass helps to avoid mistakes since the physical mass is conserved as is the total probability for all hypothetical outcomes .
Measure theoretic formulation
A probability mass function of a discrete random variable can be seen as a special case of two more general measure theoretic constructions:
the distribution of and the probability density function of with respect to the counting measure. We make this more precise below.
Suppose that is a probability space
and that is a measurable space whose underlying σ-algebra is discrete, so in particular contains singleton sets of . In this setting, a random variable is discrete provided its image is countable.
The pushforward measure —called the distribution of in this context—is a probability measure on whose restriction to singleton sets induces the probability mass function (as mentioned in the previous section) since for each .
Now suppose that is a measure space equipped with the counting measure . The probability density function of with respect to the counting measure, if it exists, is the Radon–Nikodym derivative of the pushforward measure of (with respect to the counting measure), so and is a function from to the non-negative reals. As a consequence, for any we have
demonstrating that is in fact a probability mass function. | Probability mass function | Wikipedia | 462 | 154725 | https://en.wikipedia.org/wiki/Probability%20mass%20function | Mathematics | Probability | null |
When there is a natural order among the potential outcomes , it may be convenient to assign numerical values to them (or n-tuples in case of a discrete multivariate random variable) and to consider also values not in the image of . That is, may be defined for all real numbers and for all as shown in the figure.
The image of has a countable subset on which the probability mass function is one. Consequently, the probability mass function is zero for all but a countable number of values of .
The discontinuity of probability mass functions is related to the fact that the cumulative distribution function of a discrete random variable is also discontinuous. If is a discrete random variable, then means that the casual event is certain (it is true in 100% of the occurrences); on the contrary, means that the casual event is always impossible. This statement isn't true for a continuous random variable , for which for any possible . Discretization is the process of converting a continuous random variable into a discrete one.
Examples
Finite
There are three major distributions associated, the Bernoulli distribution, the binomial distribution and the geometric distribution. | Probability mass function | Wikipedia | 235 | 154725 | https://en.wikipedia.org/wiki/Probability%20mass%20function | Mathematics | Probability | null |
Bernoulli distribution: ber(p) , is used to model an experiment with only two possible outcomes. The two outcomes are often encoded as 1 and 0. An example of the Bernoulli distribution is tossing a coin. Suppose that is the sample space of all outcomes of a single toss of a fair coin, and is the random variable defined on assigning 0 to the category "tails" and 1 to the category "heads". Since the coin is fair, the probability mass function is
Binomial distribution, models the number of successes when someone draws n times with replacement. Each draw or experiment is independent, with two possible outcomes. The associated probability mass function is . An example of the binomial distribution is the probability of getting exactly one 6 when someone rolls a fair die three times.
Geometric distribution describes the number of trials needed to get one success. Its probability mass function is .An example is tossing a coin until the first "heads" appears. denotes the probability of the outcome "heads", and denotes the number of necessary coin tosses. Other distributions that can be modeled using a probability mass function are the categorical distribution (also known as the generalized Bernoulli distribution) and the multinomial distribution.
If the discrete distribution has two or more categories one of which may occur, whether or not these categories have a natural ordering, when there is only a single trial (draw) this is a categorical distribution.
An example of a multivariate discrete distribution, and of its probability mass function, is provided by the multinomial distribution. Here the multiple random variables are the numbers of successes in each of the categories after a given number of trials, and each non-zero probability mass gives the probability of a certain combination of numbers of successes in the various categories.
Infinite
The following exponentially declining distribution is an example of a distribution with an infinite number of possible outcomes—all the positive integers: Despite the infinite number of possible outcomes, the total probability mass is 1/2 + 1/4 + 1/8 + ⋯ = 1, satisfying the unit total probability requirement for a probability distribution.
Multivariate case
Two or more discrete random variables have a joint probability mass function, which gives the probability of each possible combination of realizations for the random variables. | Probability mass function | Wikipedia | 464 | 154725 | https://en.wikipedia.org/wiki/Probability%20mass%20function | Mathematics | Probability | null |
Pentlandite is an iron–nickel sulfide with the chemical formula . Pentlandite has a narrow variation range in nickel to iron ratios (Ni:Fe), but it is usually described as 1:1. In some cases, this ratio is skewed by the presence of pyrrhotite inclusions. It also contains minor cobalt, usually at low levels as a fraction of weight.
Pentlandite forms isometric crystals, but it is normally found in massive granular aggregates. It is brittle with a hardness of 3.5–4 and specific gravity of 4.6–5.0 and is non-magnetic. It has a yellowish bronze color and a metallic luster.
Pentlandite is found in abundance within ultramafic rocks, making it one of the most important sources of mined nickel. It also occasionally occurs within mantle xenoliths and "black smoker" hydrothermal vents.
Etymology
It is named after Irish scientist Joseph Barclay Pentland (1797–1873), who first noted the mineral at Sudbury, Ontario.
Identification
Physical and optical properties
In the field, pentlandite is often confused with other sulfide minerals, as they are all brassy yellowish in color and have a metallic luster. For this reason, the best way to discern pentlandite is by its paler color, lack of magnetism, and light brownish bronze streak. In contrast, pyrite, pyrrhotite and chalcopyrite will all display much darker streaks: brownish black, greyish black, greenish black respectively. When looked at using reflected light ore microscopy, it possesses key diagnostic properties such as octahedral cleavage, and its alteration to bravoite, a pinkish to brownish violet sulfide mineral that occurs in euhedral to octahedral crystals. Pentlandite usually develops as granular inclusions within other sulfide minerals (mainly pyrrhotite), often taking the shape of thin veins or "flames". Although pentlandite is an opaque mineral, it exhibits a strong light creamy reflectance.
Mineral associations
Pentlandite occurs alongside sulfide minerals such as bravoite, chalcopyrite, cubanite, millerite, pyrrhotite, valleriite, as well as other minerals like chromite, ilmenite, magnetite, and sperrylite. It is chemically similar to mackinawite, godlevskite and horomanite. | Pentlandite | Wikipedia | 500 | 154735 | https://en.wikipedia.org/wiki/Pentlandite | Physical sciences | Minerals | Earth science |
Pentlandite is synonymous with folgerite, horbachite, lillhammerite, and nicopyrite.
Pentlandite group
The pentlandite group is a subdivision of rare minerals that share similar chemical and structural properties with pentlandite, hence the name. Their chemical formula can be written as XY8(S, Se)8 in which X is usually replaced by silver, manganese, cadmium, and lead, while copper takes the place of Y. Iron, nickel, and cobalt have the ability to occupy both X or Y positions. These minerals are:
Argentopentlandite Ag(Fe,Ni)8S8
Cobalt pentlandite Co9S8
Geffroyite (Ag,Cu,Fe)9(Se,S)8
Manganese-shadlunite (Mn,Pb)(Cu,Fe)8S8
Shadlunite (Pb,Cd)(Fe,Cu)8S8
Oberthürite Rh3Ni32S32
Sugakiite Cu(Fe,Ni)8S8
Paragenesis
Pentlandite is the most common terrestrial nickel sulfide. It typically forms during cooling of a sulfide melt. These sulfide melts, in turn, are typically formed during the evolution of a silicate melt. Because nickel is a chalcophile element, it has preference for (i.e. it "partitions into") sulfide phases. In sulfide undersaturated melts, nickel substitutes for other transition metals within ferromagnesian minerals, the most common being olivine, as well as nickeliferous varieties of amphibole, biotite, pyroxene and spinel. Nickel substitutes most readily for Fe2+ and Co2+ because or their similarity in size and charge.
In sulfide saturated melts, nickel behaves as a chalcophile element and partitions strongly into the sulfide phase. Because most nickel behaves as a compatible element in igneous differentiation processes, the formation of nickel-bearing sulfides is essentially restricted to sulfide saturated mafic and ultramafic melts. Minor amounts of nickel sulfides are found in mantle peridotites. | Pentlandite | Wikipedia | 458 | 154735 | https://en.wikipedia.org/wiki/Pentlandite | Physical sciences | Minerals | Earth science |
The behaviour of sulfide melts is complex and is affected by copper, nickel, iron, and sulfur ratios. Typically, above 1100 °C, only one sulfide melt exists. Upon cooling to 1000 °C, a solid containing mostly Fe and minor amounts of Ni and Cu is formed. This phase is called monosulfide solid solution (MSS), and is unstable at low temperatures decomposing to mixtures of pentlandite and pyrrhotite, and (rarely) pyrite. It is only upon cooling past ~ (dependent on composition) that the MSS undergoes exsolution. A separate phase, usually a copper-rich sulfide liquid may also form, giving rise to chalcopyrite upon cooling.
These phases typically form aphanitic equigranular massive sulfides, or are present as disseminated sulfides within rocks composed mostly of silicates. Pristine magmatic massive sulfide are rarely preserved as most deposits of nickeliferous sulfide have been metamorphosed.
Metamorphism at a grade equal to, or higher than, greenschist facies will cause solid massive sulfides to deform in a ductile fashion and to travel some distance into the country rock and along structures. Upon cessation of metamorphism, the sulfides may inherit a foliated or sheared texture, and typically develop bright, equigranular to globular aggregates of porphyroblastic pentlandite crystals known colloquially as "fish scales".
Metamorphism may also alter the concentration of nickel and the Ni:Fe ratio and Ni:S ratio of the sulfides. In this case, pentlandite may be replaced by millerite, and rarely heazlewoodite. Metamorphism may also be associated with metasomatism, and it is particularly common for arsenic to react with pre-existing sulfides, producing nickeline, gersdorffite and other Ni–Co arsenides.
Occurrence
Pentlandite is found within the lower margins of mineralized layered intrusions, the best examples being the Bushveld igneous complex, South Africa, the Voisey's Bay troctolite intrusive complex in Canada, the Duluth gabbro, in North America, and various other localities throughout the world. In these locations, pentlandite is considered an important nickel ore. | Pentlandite | Wikipedia | 488 | 154735 | https://en.wikipedia.org/wiki/Pentlandite | Physical sciences | Minerals | Earth science |
Pentlandite is also the dominant ore mineral occurring in Kambalda type komatiitic nickel ore deposits, the prime example of which can be found in the Yilgarn Craton of Western Australia. Similar deposits exist at Nkomati, Namibia, in the Thompson Belt, Canada, and a few examples from Brazil.
Pentlandite, but primarily chalcopyrite and PGEs, are also obtained from the supergiant Norilsk nickel deposit, in trans-Siberian Russia.
The Sudbury Basin in Ontario, Canada, is associated with a large meteorite impact crater. The pentlandite-chalcopyrite-pyrrhotite ore around the Sudbury Structure formed from sulfide melts that segregated from the melt sheet produced by the impact.
Gallery | Pentlandite | Wikipedia | 156 | 154735 | https://en.wikipedia.org/wiki/Pentlandite | Physical sciences | Minerals | Earth science |
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.
Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule.
Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion, which is done by sulfate-reducing microorganisms. It also occurs in volcanic gases, natural gas deposits, and sometimes in well-drawn water.
Properties
Hydrogen sulfide is slightly denser than air. A mixture of and air can be explosive.
Oxidation
In general, hydrogen sulfide acts as a reducing agent, as indicated by its ability to reduce sulfur dioxide in the Claus process. Hydrogen sulfide burns in oxygen with a blue flame to form sulfur dioxide () and water:
If an excess of oxygen is present, sulfur trioxide () is formed, which quickly hydrates to sulfuric acid:
Acid-base properties
It is slightly soluble in water and acts as a weak acid (pKa = 6.9 in 0.01–0.1 mol/litre solutions at 18 °C), giving the hydrosulfide ion . Hydrogen sulfide and its solutions are colorless. When exposed to air, it slowly oxidizes to form elemental sulfur, which is not soluble in water. The sulfide anion is not formed in aqueous solution. | Hydrogen sulfide | Wikipedia | 419 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Extreme temperatures and pressures
At pressures above 90 GPa (gigapascal), hydrogen sulfide becomes a metallic conductor of electricity. When cooled below a critical temperature this high-pressure phase exhibits superconductivity. The critical temperature increases with pressure, ranging from 23 K at 100 GPa to 150 K at 200 GPa. If hydrogen sulfide is pressurized at higher temperatures, then cooled, the critical temperature reaches , the highest accepted superconducting critical temperature as of 2015. By substituting a small part of sulfur with phosphorus and using even higher pressures, it has been predicted that it may be possible to raise the critical temperature to above and achieve room-temperature superconductivity.
Hydrogen sulfide decomposes without a presence of a catalyst under atmospheric pressure around 1200 °C into hydrogen and sulfur.
Tarnishing
Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble, often dark colored solids. Lead(II) acetate paper is used to detect hydrogen sulfide because it readily converts to lead(II) sulfide, which is black. Treating metal sulfides with strong acid or electrolysis often liberates hydrogen sulfide. Hydrogen sulfide is also responsible for tarnishing on various metals including copper and silver; the chemical responsible for black toning found on silver coins is silver sulfide (), which is produced when the silver on the surface of the coin reacts with atmospheric hydrogen sulfide. Coins that have been subject to toning by hydrogen sulfide and other sulfur-containing compounds may have the toning add to the numismatic value of a coin based on aesthetics, as the toning may produce thin-film interference, resulting in the coin taking on an attractive coloration. Coins can also be intentionally treated with hydrogen sulfide to induce toning, though artificial toning can be distinguished from natural toning, and is generally criticised among collectors.
Production
Hydrogen sulfide is most commonly obtained by its separation from sour gas, which is natural gas with a high content of . It can also be produced by treating hydrogen with molten elemental sulfur at about 450 °C. Hydrocarbons can serve as a source of hydrogen in this process.
The very favorable thermodynamics for the hydrogenation of sulfur implies that the dehydrogenation (or cracking) of hydrogen sulfide would require very high temperatures.
A standard lab preparation is to treat ferrous sulfide with a strong acid in a Kipp generator: | Hydrogen sulfide | Wikipedia | 505 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
For use in qualitative inorganic analysis, thioacetamide is used to generate :
Many metal and nonmetal sulfides, e.g. aluminium sulfide, phosphorus pentasulfide, silicon disulfide liberate hydrogen sulfide upon exposure to water:
This gas is also produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen.
It can also be produced by mixing ammonium thiocyanate to concentrated sulphuric acid and adding water to it.
Biosynthesis
Hydrogen sulfide can be generated in cells via enzymatic or non-enzymatic pathways. Three enzymes catalyze formation of : cystathionine γ-lyase (CSE), cystathionine β-synthetase (CBS), and 3-mercaptopyruvate sulfurtransferase (3-MST). CBS and CSE are the main proponents of biogenesis, which follows the trans-sulfuration pathway. These enzymes have been identified in a breadth of biological cells and tissues, and their activity is induced by a number of disease states. These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule. 3-MST also contributes to hydrogen sulfide production by way of the cysteine catabolic pathway. Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can also be derived from proteins such as ferredoxins and Rieske proteins.
Sulfate-reducing (resp. sulfur-reducing) bacteria generate usable energy under low-oxygen conditions by using sulfates (resp. elemental sulfur) to oxidize organic compounds or hydrogen; this produces hydrogen sulfide as a waste product.
Water heaters can aid the conversion of sulfate in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, which is usually made from magnesium metal.
Signalling role
in the body acts as a gaseous signaling molecule with implications for health and in diseases. | Hydrogen sulfide | Wikipedia | 468 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Hydrogen sulfide is involved in vasodilation in animals, as well as in increasing seed germination and stress responses in plants. Hydrogen sulfide signaling is moderated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). has been shown to interact with the NO pathway resulting in several different cellular effects, including the inhibition of cGMP phosphodiesterases, as well as the formation of another signal called nitrosothiol. Hydrogen sulfide is also known to increase the levels of glutathione, which acts to reduce or disrupt ROS levels in cells.
The field of biology has advanced from environmental toxicology to investigate the roles of endogenously produced in physiological conditions and in various pathophysiological states. has been implicated in cancer, in Down syndrome and in vascular disease.
At lower concentrations, it stimulates mitochondrial function via multiple mechanisms including direct electron donation. However, at higher concentrations, it inhibits Complex IV of the mitochondrial electron transport chain, which effectively reduces ATP generation and biochemical activity within cells.
Uses
Production of sulfur
Hydrogen sulfide is mainly consumed as a precursor to elemental sulfur. This conversion, called the Claus process, involves partial oxidation to sulfur dioxide. The latter reacts with hydrogen sulfide to give elemental sulfur. The conversion is catalyzed by alumina.
Production of thioorganic compounds
Many fundamental organosulfur compounds are produced using hydrogen sulfide. These include methanethiol, ethanethiol, and thioglycolic acid. Hydrosulfides can be used in the production of thiophenol.
Production of metal sulfides
Upon combining with alkali metal bases, hydrogen sulfide converts to alkali hydrosulfides such as sodium hydrosulfide and sodium sulfide:
Sodium sulfides are used in the paper making industry. Specifically, salts of break bonds between lignin and cellulose components of pulp in the Kraft process.
As indicated above, many metal ions react with hydrogen sulfide to give the corresponding metal sulfides. Oxidic ores are sometimes treated with hydrogen sulfide to give the corresponding metal sulfides which are more readily purified by flotation. Metal parts are sometimes passivated with hydrogen sulfide. Catalysts used in hydrodesulfurization are routinely activated with hydrogen sulfide. | Hydrogen sulfide | Wikipedia | 481 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Hydrogen sulfide was a reagent in the qualitative inorganic analysis of metal ions. In these analyses, heavy metal (and nonmetal) ions (e.g., Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to . The components of the resulting solid are then identified by their reactivity.
Miscellaneous applications
Hydrogen sulfide is used to separate deuterium oxide, or heavy water, from normal water via the Girdler sulfide process.
A suspended animation-like state has been induced in rodents with the use of hydrogen sulfide, resulting in hypothermia with a concomitant reduction in metabolic rate. Oxygen demand was also reduced, thereby protecting against hypoxia. In addition, hydrogen sulfide has been shown to reduce inflammation in various situations.
Occurrence
Volcanoes and some hot springs (as well as cold springs) emit some . Hydrogen sulfide can be present naturally in well water, often as a result of the action of sulfate-reducing bacteria. Hydrogen sulfide is produced by the human body in small quantities through bacterial breakdown of proteins containing sulfur in the intestinal tract; it therefore contributes to the characteristic odor of flatulence. It is also produced in the mouth (halitosis).
A portion of global emissions are due to human activity. By far the largest industrial source of is petroleum refineries: The hydrodesulfurization process liberates sulfur from petroleum by the action of hydrogen. The resulting is converted to elemental sulfur by partial combustion via the Claus process, which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include coke ovens, paper mills (using the Kraft process), tanneries and sewerage. arises from virtually anywhere where elemental sulfur comes in contact with organic material, especially at high temperatures. Depending on environmental conditions, it is responsible for deterioration of material through the action of some sulfur oxidizing microorganisms. It is called biogenic sulfide corrosion.
In 2011 it was reported that increased concentrations of were observed in the Bakken formation crude, possibly due to oil field practices, and presented challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements". | Hydrogen sulfide | Wikipedia | 485 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Besides living near gas and oil drilling operations, ordinary citizens can be exposed to hydrogen sulfide by being near waste water treatment facilities, landfills and farms with manure storage. Exposure occurs through breathing contaminated air or drinking contaminated water.
In municipal waste landfill sites, the burial of organic material rapidly leads to the production of anaerobic digestion within the waste mass and, with the humid atmosphere and relatively high temperature that accompanies biodegradation, biogas is produced as soon as the air within the waste mass has been reduced. If there is a source of sulfate bearing material, such as plasterboard or natural gypsum (calcium sulfate dihydrate), under anaerobic conditions sulfate reducing bacteria converts this to hydrogen sulfide. These bacteria cannot survive in air but the moist, warm, anaerobic conditions of buried waste that contains a high source of carbon – in inert landfills, paper and glue used in the fabrication of products such as plasterboard can provide a rich source of carbon – is an excellent environment for the formation of hydrogen sulfide.
In industrial anaerobic digestion processes, such as waste water treatment or the digestion of organic waste from agriculture, hydrogen sulfide can be formed from the reduction of sulfate and the degradation of amino acids and proteins within organic compounds. Sulfates are relatively non-inhibitory to methane forming bacteria but can be reduced to by sulfate reducing bacteria, of which there are several genera.
Removal from water
A number of processes have been designed to remove hydrogen sulfide from drinking water.
Continuous chlorination For levels up to 75 mg/L chlorine is used in the purification process as an oxidizing chemical to react with hydrogen sulfide. This reaction yields insoluble solid sulfur. Usually the chlorine used is in the form of sodium hypochlorite.
Aeration For concentrations of hydrogen sulfide less than 2 mg/L aeration is an ideal treatment process. Oxygen is added to water and a reaction between oxygen and hydrogen sulfide react to produce odorless sulfate.
Nitrate addition Calcium nitrate can be used to prevent hydrogen sulfide formation in wastewater streams. | Hydrogen sulfide | Wikipedia | 434 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Removal from fuel gases
Hydrogen sulfide is commonly found in raw natural gas and biogas. It is typically removed by amine gas treating technologies. In such processes, the hydrogen sulfide is first converted to an ammonium salt, whereas the natural gas is unaffected.
The bisulfide anion is subsequently regenerated by heating of the amine sulfide solution. Hydrogen sulfide generated in this process is typically converted to elemental sulfur using the Claus Process.
Safety
The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is stinkdamp. Hydrogen sulfide is a highly toxic and flammable gas (flammable range: 4.3–46%). It can poison several systems in the body, although the nervous system is most affected. The toxicity of is comparable with that of carbon monoxide. It binds with iron in the mitochondrial cytochrome enzymes, thus preventing cellular respiration. Its toxic properties were described in detail in 1843 by Justus von Liebig.
Even before hydrogen sulfide was discovered, Italian physician Bernardino Ramazzini hypothesized in his 1713 book De Morbis Artificum Diatriba that occupational diseases of sewer-workers and blackening of coins in their clothes may be caused by an unknown invisible volatile acid (moreover, in late 18th century toxic gas emanation from Paris sewers became a problem for the citizens and authorities).
Although very pungent at first (it smells like rotten eggs), it quickly deadens the sense of smell, creating temporary anosmia, so victims may be unaware of its presence until it is too late. Safe handling procedures are provided by its safety data sheet (SDS).
Low-level exposure
Since hydrogen sulfide occurs naturally in the body, the environment, and the gut, enzymes exist to metabolize it. At some threshold level, believed to average around 300–350 ppm, the oxidative enzymes become overwhelmed. Many personal safety gas detectors, such as those used by utility, sewage and petrochemical workers, are set to alarm at as low as 5 to 10 ppm and to go into high alarm at 15 ppm. Metabolism causes oxidation to sulfate, which is harmless. Hence, low levels of hydrogen sulfide may be tolerated indefinitely. | Hydrogen sulfide | Wikipedia | 464 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Exposure to lower concentrations can result in eye irritation, a sore throat and cough, nausea, shortness of breath, and fluid in the lungs. These effects are believed to be due to hydrogen sulfide combining with alkali present in moist surface tissues to form sodium sulfide, a caustic. These symptoms usually subside in a few weeks.
Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness. Chronic exposure to low level (around 2 ppm) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers, but the reports have not (as of 1995) been replicated.
High-level exposure
Short-term, high-level exposure can induce immediate collapse, with loss of breathing and a high probability of death. If death does not occur, high exposure to hydrogen sulfide can lead to cortical pseudolaminar necrosis, degeneration of the basal ganglia and cerebral edema. Although respiratory paralysis may be immediate, it can also be delayed up to 72 hours.
Inhalation of resulted in about 7 workplace deaths per year in the U.S. (2011–2017 data), second only to carbon monoxide (17 deaths per year) for workplace chemical inhalation deaths.
Exposure thresholds | Hydrogen sulfide | Wikipedia | 276 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Exposure limits stipulated by the United States government:
10 ppm REL-Ceiling (NIOSH): recommended permissible exposure ceiling (the recommended level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs)
20 ppm PEL-Ceiling (OSHA): permissible exposure ceiling (the level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs)
50 ppm PEL-Peak (OSHA): peak permissible exposure (the level that must never be exceeded)
100 ppm IDLH (NIOSH): immediately dangerous to life and health (the level that interferes with the ability to escape)
0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it.
10–20 ppm is the borderline concentration for eye irritation.
50–100 ppm leads to eye damage.
At 100–150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.
320–530 ppm leads to pulmonary edema with the possibility of death.
530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing.
800 ppm is the lethal concentration for 50% of humans for 5 minutes' exposure (LC50).
Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.
Treatment
Treatment involves immediate inhalation of amyl nitrite, injections of sodium nitrite, or administration of 4-dimethylaminophenol in combination with inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm, and in some cases hyperbaric oxygen therapy (HBOT). HBOT has clinical and anecdotal support.
Incidents
Hydrogen sulfide was used by the British Army as a chemical weapon during World War I. It was not considered to be an ideal war gas, partially due to its flammability and because the distinctive smell could be detected from even a small leak, alerting the enemy to the presence of the gas. It was nevertheless used on two occasions in 1916 when other gases were in short supply. | Hydrogen sulfide | Wikipedia | 504 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
On September 2, 2005, a leak in the propeller room of a Royal Caribbean Cruise Liner docked in Los Angeles resulted in the deaths of 3 crewmen due to a sewage line leak. As a result, all such compartments are now required to have a ventilation system.
A dump of toxic waste containing hydrogen sulfide is believed to have caused 17 deaths and thousands of illnesses in Abidjan, on the West African coast, in the 2006 Côte d'Ivoire toxic waste dump.
In September 2008, three workers were killed and two suffered serious injury, including long term brain damage, at a mushroom growing company in Langley, British Columbia. A valve to a pipe that carried chicken manure, straw and gypsum to the compost fuel for the mushroom growing operation became clogged, and as workers unclogged the valve in a confined space without proper ventilation the hydrogen sulfide that had built up due to anaerobic decomposition of the material was released, poisoning the workers in the surrounding area. An investigator said there could have been more fatalities if the pipe had been fully cleared and/or if the wind had changed directions.
In 2014, levels of hydrogen sulfide as high as 83 ppm were detected at a recently built mall in Thailand called Siam Square One at the Siam Square area. Shop tenants at the mall reported health complications such as sinus inflammation, breathing difficulties and eye irritation. After investigation it was determined that the large amount of gas originated from imperfect treatment and disposal of waste water in the building.
In 2014, hydrogen sulfide gas killed workers at the Promenade shopping center in North Scottsdale, Arizona, USA after climbing into 15 ft deep chamber without wearing personal protective gear. "Arriving crews recorded high levels of hydrogen cyanide and hydrogen sulfide coming out of the sewer."
In November 2014, a substantial amount of hydrogen sulfide gas shrouded the central, eastern and southeastern parts of Moscow. Residents living in the area were urged to stay indoors by the emergencies ministry. Although the exact source of the gas was not known, blame had been placed on a Moscow oil refinery. | Hydrogen sulfide | Wikipedia | 423 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
In June 2016, a mother and her daughter were found dead in their still-running 2006 Porsche Cayenne SUV against a guardrail on Florida's Turnpike, initially thought to be victims of carbon monoxide poisoning. Their deaths remained unexplained as the medical examiner waited for results of toxicology tests on the victims, until urine tests revealed that hydrogen sulfide was the cause of death. A report from the Orange-Osceola Medical Examiner's Office indicated that toxic fumes came from the Porsche's starter battery, located under the front passenger seat.
In January 2017, three utility workers in Key Largo, Florida, died one by one within seconds of descending into a narrow space beneath a manhole cover to check a section of paved street. In an attempt to save the men, a firefighter who entered the hole without his air tank (because he could not fit through the hole with it) collapsed within seconds and had to be rescued by a colleague. The firefighter was airlifted to Jackson Memorial Hospital and later recovered. A Monroe County Sheriff officer initially determined that the space contained hydrogen sulfide and methane gas produced by decomposing vegetation. | Hydrogen sulfide | Wikipedia | 236 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
On May 24, 2018, two workers were killed, another seriously injured, and 14 others hospitalized by hydrogen sulfide inhalation at a Norske Skog paper mill in Albury, New South Wales. An investigation by SafeWork NSW found that the gas was released from a tank used to hold process water. The workers were exposed at the end of a 3-day maintenance period. Hydrogen sulfide had built up in an upstream tank, which had been left stagnant and untreated with biocide during the maintenance period. These conditions allowed sulfate-reducing bacteria to grow in the upstream tank, as the water contained small quantities of wood pulp and fiber. The high rate of pumping from this tank into the tank involved in the incident caused hydrogen sulfide gas to escape from various openings around its top when pumping was resumed at the end of the maintenance period. The area above it was sufficiently enclosed for the gas to pool there, despite not being identified as a confined space by Norske Skog. One of the workers who was killed was exposed while investigating an apparent fluid leak in the tank, while the other who was killed and the worker who was badly injured were attempting to rescue the first after he collapsed on top of it. In a resulting criminal case, Norske Skog was accused of failing to ensure the health and safety of its workforce at the plant to a reasonably practicable extent. It pleaded guilty, and was fined AU$1,012,500 and ordered to fund the production of an anonymized educational video about the incident.
In October 2019, an Odessa, Texas employee of Aghorn Operating Inc. and his wife were killed due to a water pump failure. Produced water with a high concentration of hydrogen sulfide was released by the pump. The worker died while responding to an automated phone call he had received alerting him to a mechanical failure in the pump, while his wife died after driving to the facility to check on him. A CSB investigation cited lax safety practices at the facility, such as an informal lockout-tagout procedure and a nonfunctioning hydrogen sulfide alert system.
Suicides
The gas, produced by mixing certain household ingredients, was used in a suicide wave in 2008 in Japan. The wave prompted staff at Tokyo's suicide prevention center to set up a special hotline during "Golden Week", as they received an increase in calls from people wanting to kill themselves during the annual May holiday. | Hydrogen sulfide | Wikipedia | 496 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
As of 2010, this phenomenon has occurred in a number of US cities, prompting warnings to those arriving at the site of the suicide. These first responders, such as emergency services workers or family members are at risk of death or injury from inhaling the gas, or by fire. Local governments have also initiated campaigns to prevent such suicides.
In 2020, ingestion was used as a suicide method by Japanese pro wrestler Hana Kimura.
In 2024, Lucy-Bleu Knight, stepdaughter of famed musician Slash, also used ingestion to commit suicide.
Hydrogen sulfide in the natural environment
Microbial: The sulfur cycle
Hydrogen sulfide is a central participant in the sulfur cycle, the biogeochemical cycle of sulfur on Earth.
In the absence of oxygen, sulfur-reducing and sulfate-reducing bacteria derive energy from oxidizing hydrogen or organic molecules by reducing elemental sulfur or sulfate to hydrogen sulfide. Other bacteria liberate hydrogen sulfide from sulfur-containing amino acids; this gives rise to the odor of rotten eggs and contributes to the odor of flatulence.
As organic matter decays under low-oxygen (or hypoxic) conditions (such as in swamps, eutrophic lakes or dead zones of oceans), sulfate-reducing bacteria will use the sulfates present in the water to oxidize the organic matter, producing hydrogen sulfide as waste. Some of the hydrogen sulfide will react with metal ions in the water to produce metal sulfides, which are not water-soluble. These metal sulfides, such as ferrous sulfide FeS, are often black or brown, leading to the dark color of sludge.
Several groups of bacteria can use hydrogen sulfide as fuel, oxidizing it to elemental sulfur or to sulfate by using dissolved oxygen, metal oxides (e.g., iron oxyhydroxides and manganese oxides), or nitrate as electron acceptors.
The purple sulfur bacteria and the green sulfur bacteria use hydrogen sulfide as an electron donor in photosynthesis, thereby producing elemental sulfur. This mode of photosynthesis is older than the mode of cyanobacteria, algae, and plants, which uses water as electron donor and liberates oxygen. | Hydrogen sulfide | Wikipedia | 464 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
The biochemistry of hydrogen sulfide is a key part of the chemistry of the iron-sulfur world. In this model of the origin of life on Earth, geologically produced hydrogen sulfide is postulated as an electron donor driving the reduction of carbon dioxide.
Animals
Hydrogen sulfide is lethal to most animals, but a few highly specialized species (extremophiles) do thrive in habitats that are rich in this compound.
In the deep sea, hydrothermal vents and cold seeps with high levels of hydrogen sulfide are home to a number of extremely specialized lifeforms, ranging from bacteria to fish. Because of the absence of sunlight at these depths, these ecosystems rely on chemosynthesis rather than photosynthesis.
Freshwater springs rich in hydrogen sulfide are mainly home to invertebrates, but also include a small number of fish: Cyprinodon bobmilleri (a pupfish from Mexico), Limia sulphurophila (a poeciliid from the Dominican Republic), Gambusia eurystoma (a poeciliid from Mexico), and a few Poecilia (poeciliids from Mexico). Invertebrates and microorganisms in some cave systems, such as Movile Cave, are adapted to high levels of hydrogen sulfide.
Interstellar and planetary occurrence
Hydrogen sulfide has often been detected in the interstellar medium. It also occurs in the clouds of planets in our solar system.
Mass extinctions
Hydrogen sulfide has been implicated in several mass extinctions that have occurred in the Earth's past. In particular, a buildup of hydrogen sulfide in the atmosphere may have caused, or at least contributed to, the Permian-Triassic extinction event 252 million years ago.
Organic residues from these extinction boundaries indicate that the oceans were anoxic (oxygen-depleted) and had species of shallow plankton that metabolized . The formation of may have been initiated by massive volcanic eruptions, which emitted carbon dioxide and methane into the atmosphere, which warmed the oceans, lowering their capacity to absorb oxygen that would otherwise oxidize . The increased levels of hydrogen sulfide could have killed oxygen-generating plants as well as depleted the ozone layer, causing further stress. Small blooms have been detected in modern times in the Dead Sea and in the Atlantic Ocean off the coast of Namibia. | Hydrogen sulfide | Wikipedia | 470 | 154738 | https://en.wikipedia.org/wiki/Hydrogen%20sulfide | Physical sciences | Hydrogen compounds | Chemistry |
Dubai International Airport () is the primary international airport serving Dubai, United Arab Emirates, and is the world's busiest airport by international passenger traffic as of 2023. It is also the busiest airport in the Middle East as of 2023, the second-busiest airport in the world by passenger traffic as of 2023, the busiest airport for Airbus A380 and Boeing 777 movements, and the airport with the highest average number of passengers per flight. In 2023, the airport handled 87 million passengers and 1.81 million tonnes of cargo and registered 416,405 aircraft movements.
Dubai International Airport is situated in the Al Garhoud district, east of the city center of Dubai and spread over an area of of land. Terminal 3 is the third-largest building in the world by floor space and the largest airport terminal in the world. In July 2019, Dubai International airport installed the largest solar energy system in the region's airports as part of Dubai's goal to reduce 30 per cent of the city energy consumption by 2030.
Emirates Airline has its hub airport in Dubai International (DXB) and has its own terminal 3 with three concourses that they share with Flydubai. The Emirates hub is the largest airline hub in the Middle East; Emirates handles 51% of all passenger traffic and accounts for approximately 42% of all aircraft movements at the airport. Dubai Airport is also the base for low-cost carrier flydubai which handles 13% of passenger traffic and 25% of aircraft movements at DXB. The airport has a total capacity of 90 million passengers annually. As of January 2024, over 8,000 weekly flights are operated by 100 airlines to over 262 destinations across all inhabited continents. Over 63% of travelers using the airport in 2018 were connecting passengers.
In 2014, Dubai International indirectly supported over 400,000 jobs and contributed over US$26.7 billion to the economy, representing around 27% of Dubai's GDP and 21% of the employment in Dubai.
Due to the announced expansion of Al Maktoum Airport on 28 April 2024, Dubai International Airport will be shut down once Al Maktoum Airport expansion will be completed. | Dubai International Airport | Wikipedia | 440 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
History
The history of civil aviation in Dubai started in July 1937 when an air agreement was signed for a flying boat base for aircraft of Imperial Airways with the rental of the base at about 440 rupees per month – this included the guards' wages. The Empire Flying Boats started operating once a week flying eastbound to Karachi from the UK and westbound to Southampton, England. By February 1938, there were four flying boats a week.
In the 1940s, flying from Dubai was by flying boats operated by British Overseas Airways Corporation (BOAC), operating the Horseshoe route from Southern Africa via the Persian Gulf to Sydney.
Construction
Construction of the airport was ordered bby the ruler of Dubai, Sheikh Rashid bin Saeed Al Maktoum, in 1959. It officially opened on 30 September 1960, at which time it was able to handle aircraft the size of a Douglas DC-3 on a runway made of compacted sand. Three turning-areas, an apron and small terminal completed the airport that was constructed by Costain.
In May 1963, construction of a asphalt runway started. This new runway, alongside the original sand runway and taxiway opened in May 1965, together with several new extensions to the terminal Building, hangars were erected, and Airport and Navigational aids were installed. The installation of the lighting system continued after the official opening and was completed in August 1965. During the second half of the 1960s several extensions, equipment upgrades like a VHF omnidirectional range (VOR) and an instrument landing system (ILS), as well as new buildings, were constructed. By 1969, the airport was served by 9 airlines serving some 20 destinations.
The inauguration on 15 May 1966 was marked by the visits of the first big jets, De Havilland Comets of Middle East Airlines and Kuwait Airways.
The advent of wide-body aircraft required further airport development in the 1970s and plans for a new terminal, runways, and taxiways capable of coping with international flights were drawn up. The construction of a new terminal building consisting of a three-story building long with an enclosed floor area of . A new control tower was also constructed.
Expansion continued in the early 1970s including ILS Category II equipment, lengthening the existing runway to , installation of a non-directional beacon (NDB), diesel generators, taxiways, etc. This work made handling the Boeing 747 and Concorde possible. Several runway and apron extensions were carried out through the decade to meet growing demand. | Dubai International Airport | Wikipedia | 494 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
The new precision category 2 Approach and Runway Lighting System was commissioned in 1971. The construction of the Airport Fire Station and the installation of the generators were completed in December 1971 and were fully operational in March 1972. The ruler of Dubai also commissioned and inaugurated the Long-range Surveillance System on 19 June 1973.
With the expansion of the Airport Fire Services, it became necessary to find more suitable hangars. A hangar-style building was made available for use at the end of 1976. This building was strategically located midway between the runway ends to facilitate efficient operations. Additionally, a new building was constructed to house the Airport Maintenance Engineer, Electronics Engineering section, and Stores unit.
Expansion and refurbishment of the Airport Restaurant and Transit Lounge, including a new kitchen, were completed in December 1978.
The next phase of development included the construction of a new runway, which was completed three months ahead of schedule and opened in April 1984. This runway, located 360 metres north of and parallel to the existing runway, was equipped with the latest meteorological, airfield lighting, and instrument landing systems, giving the airport a Category II classification.
Several extensions and upgrades were also made to the terminal facilities and supporting systems. On December 23, 1980, the airport became an ordinary member of the Airports Council International (ACI). The decline of Karachi Airport is often attributed to the traffic Dubai diverted from it.
During the 1980s, Dubai was a stopping point for airlines such as Air India, Cathay Pacific, Singapore Airlines, Malaysia Airlines, and others traveling between Asia and Europe that needed a refueling point in the Persian Gulf. Later made redundant with the availability of Russian airspace due to the breakup of the Soviet Union and the advent of longer-range aircraft introduced in the late 1980s and early 1990s such as the Airbus A340, the Boeing 747-400 and the Boeing 777 series aircraft, which had the ability to fly between Europe and Southeast Asia nonstop. British Airways flights from Islamabad to Manchester also stopped for short times during the 1980s for refueling and supplies.
Expansion | Dubai International Airport | Wikipedia | 403 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
The opening of Terminal 2 in 1998 saw the first step of phase 1 of the new development master plan launched in 1997. In the second stage, Concourse 1, named Sheikh Rashid Terminal opened in April 2000. The concourse is in length connects to the check-in area via a tunnel containing moving walkways (conveyor belt/travelators). It also contains a hotel, business center, health club, exchanges, dining and entertainment facilities, internet services, a medical center, a post office, and a prayer room. The next step was runway reconfiguration, already part of phase 2, and aprons and taxiways were expanded and strengthened in 2003–2004. In addition, the Dubai Flower Centre opened in 2005 as part of the development. The airport saw the need for this as the city is a hub for the import and export of flowers and the airport required a specialist facility since flowers need special conditions.
Construction of Terminal 3 began in 2004 as the next stage of phase 2 of the development, with an estimated cost of around $4.55 billion. Completion was originally planned for 2006 but was delayed by two years.
On 30 May 2008, a topping-out ceremony was conducted. The terminal became operational on 14 October 2008, with Emirates Airline (EK2926) from Jeddah, Saudi Arabia, being the first flight to arrive at the new terminal and EK843 to Doha, Qatar being the first departing flight. The terminal increased the airport's maximum annual passenger capacity by 47 million, bringing the total annual capacity to 75 million passengers.
On 29 October 2010, the airport marked its 50th anniversary. The airport has seen over 402 million passengers at an average annual growth rate of 15.5% and handled over 3.87 million aircraft at an average annual growth rate of 12.4%.
With the arrival of the Airbus A380, the airport made modifications costing $230 million. These included the building of 29 gates capable of handling large aircraft, five of which are in Terminal 3 and two are in Terminal 1. Other important projects at the airport include the next stage of phase 2 development, which includes the construction of Concourse 3. This will be a smaller version of Concourse 2, connected to Terminal 3. | Dubai International Airport | Wikipedia | 449 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Also as part of the expansion, the airport now handles at least 75 million (an increase of 19 million) passengers per annum with the opening of Concourse 3, part of Terminal 3. However, recent communications predict a further increase to 80 million passengers with additional reassessments of existing capacities. In 2009, Terminal 2 expanded its facilities to handle 5 million (an increase of 2 million) passengers annually, taking the airport's total capacity to 62 million passengers. Terminal 2 capacity was planned to bring the total capacity of the airport from the initial 75 million passengers to 80 million passenger capacity by 2012.
The Cargo Mega Terminal, which will have the capacity to handle 3 million tonnes of cargo a year, is a major development; it will be built in the long term. The completion of the mega terminal will be no later than 2018. Terminal 2 will be completely redeveloped to match the status of the other two terminals. With all of these projects completed by 2013, the airport expects to handle at least 75–80 million passengers and over 5 million tonnes of cargo.
The airport's landside facilities were modified to allow the construction of two stations for the Red Line of Dubai Metro. One station was built at Terminal 1 and the other at Terminal 3. The line began service on 9 September 2009 and opened in phases over the next year. The second Metro line, the Green Line, runs near the Airport Free Zone and has served the airport's north-eastern area with the Terminal 2 starting in September 2011.
With phase 2 of DXB's expansion plan complete, the airport now has three terminals and three concourses, two cargo mega terminals, an airport-free zone, an expo center with three large exhibition halls, a major aircraft maintenance hub and a flower center to handle perishable goods. A phase 3 which has been included in the master plan involves the construction of a new Concourse 4.
The airport revealed its future plans in May 2011, which involve the construction of a new Concourse D for all airlines currently operating from Concourse C. Concourse D is expected to bring the total capacity of the airport to over 90 million passengers and will open in early 2016. The plan also involves Emirates solely operating from Concourse C along with Concourse A and B. | Dubai International Airport | Wikipedia | 451 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
In September 2012, Dubai Airports changed the names of concourses to make it easier for passengers to navigate the airport. Concourse 1, in which over 100 international airlines operate, became Concourse C (C1-C50). Concourse 2 became Concourse B (B1-B32) and Concourse 3 became Concourse A (A1-A24). The gates in Terminal 2 were changed and are now numbered F1 to F12. The remaining alpha-numeric sequences are being reserved for future airport facilities that are part of the Dubai Airports' $7.8 billion expansion programm, including Concourse D.
In December 2024, CEO Paul Griffiths declared that Dubai International Airport is rapidly expanding, with plans to enhance passenger experiences through advanced technologies like facial recognition and a focus on reducing wait times while maximizing shopping opportunities. He highlighted a $35 billion expansion of Dubai World Central, aiming to create smaller, more intimate airport experiences within a vast complex, ultimately positioning it to become the world's largest airport.
Dubai's government announced the construction of a new airport in Jebel Ali, named Dubai World Central – Al Maktoum International Airport. It is expected to be the second-largest airport in the world by physical size, though not by passenger metrics. It opened 27 June 2010; however, construction is not expected to finish until 2027. The airport is expected to be able to accommodate up to 160 million passengers. There has been an official plan to build the Dubai Metro Purple Line to connect Al Maktoum International Airport to Dubai International Airport; construction was set to begin in 2012. The proposed Purple Line will link Dubai International Airport and Al Maktoum International Airport.
Concourse D opened on 24 February 2016 for all international airlines and moved out of Terminal 1. Emirates now operates from Concourses A, B, and C, all under Terminal 3. while FlyDubai operates from Terminal 2 (Concourse F).
On 20 December 2018 the airport celebrated its one billionth passenger.
In April 2024, the airport was submerged in water by floods and suffered extensive damage.
Air traffic
Main airlines based at DXB | Dubai International Airport | Wikipedia | 424 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Emirates is the largest airline operating at the airport, with an all-wide-body fleet of over 200 Airbus and Boeing aircraft based at Dubai, providing scheduled services to the Middle East, Africa, Asia, Europe, North America, South America, Australia and New Zealand. It operates out of Terminal 3, Concourses A, B and C.
Emirates SkyCargo, a subsidiary of Emirates, operates scheduled all-cargo services between Dubai and the rest of the world.
Flydubai, a low-cost airline planning to operate over 100 aircraft on scheduled passenger services to and from Dubai, to the Middle East, Africa, Europe and South Asia. It operates from Terminal 2 and, since December 2018, also from Terminal 3 for selected destinations.
Recreational flying to Dubai is catered for by the Dubai Aviation Club, which undertakes flying training for private pilots and provides facilities for private owners.
The Government of Dubai provides short and long-range search and rescue services, police support, medical evacuation, and general-purpose flights for the airport and all VIP flights to the airport.
Statistics
Infrastructure
Dubai International Airport was conceptualized to function as Dubai's primary airport and the region's busiest for the foreseeable future without the need for relocation or the building of another airport when passenger figures increased. The area was chosen near Dubai, to attract passengers from the city of Dubai, rather than travel to the busier Sharjah International Airport. The planned location originally was Jebel Ali.
The original master plan for the existing airport initially involved a dual-terminal and one runway configuration over two phases with provisions for another two passenger terminals in the near future. Phase 1 included the construction of the first passenger terminal, the first runway, 70 aircraft parking bays, support facilities, and structures, including large maintenance hangar, the first fire station, workshops, and administrative offices, an airfreight complex, two cargo agents' buildings, in-flight catering kitchens and an control tower. Construction for the second phase would commence immediately after the completion of Phase 1 and include the second runway, 50 new aircraft parking bays in addition to the existing 70 bays, a second fire station, and a third cargo agent building.
The third phase included the construction of a new terminal (now the parts of Terminal 1's main building and Concourse C) and an additional 60 parking bays, as well as a new aircraft maintenance facility. Then, in the early 2000s (decade) a new master plan was introduced which began the development of the current concourses and terminal infrastructure. | Dubai International Airport | Wikipedia | 509 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Paul Griffiths (Dubai Airports' CEO) in his interview with Vision magazine, cited plans to build infrastructure to support the expansion of Emirates and budget airline flydubai and ascend the ranks of global aviation hubs.
Control tower
The airport traffic control tower (ATCT) was constructed as part of phase two of the then-development plan.
Terminals
Dubai International Airport has three terminals. Terminal 1 has one concourse (Concourse D), Terminal 2 is set apart from the other two main buildings and Terminal 3 is divided into Concourse A, B, and C. The cargo terminal is capable of handling 3 million tonnes of cargo annually and a general aviation terminal (GAT) is close by.
Passenger terminals
Dubai Airport has three passenger terminals. Terminals 1 and 3 are directly connected with a common transit area, with airside passengers being able to move freely between the terminals without going through immigration, while Terminal 2 is on the opposite side of the airport. For transiting passengers, a shuttle service runs between the terminals, with a journey time of around 20 minutes from Terminal 2 to Terminal 1 and 30 minutes to Terminal 3. Passengers in Terminal 3 who need to transfer between Concourse A and the rest of the Terminal have to travel via an automated people mover. Also after early 2016 when the construction of Concourse D was done, there is now an automated people mover between concourse D and Terminal 1.
Situated beside Terminal 2 is the Executive Flights Terminal, which has its own check-in facilities for premium passengers and where transportation to aircraft in any of the other terminals is by personal buggy.
The three passenger terminals have a total handling capacity of around 80 million passengers a year.
Terminals 1 and 3 cater to international passengers, whilst Terminal 2 is for budget passengers and passengers flying to the subcontinent and Persian Gulf region; Terminals 1 and 3 handle 85% of the passenger traffic, and the Executive Flights terminal is for the higher-end travelers and important guests.
Terminal 1
Terminal 1 has a capacity of 45 million passengers. It is used by over 100 airlines and is connected to Concourse D by an automated people mover. It is spread over an area of and offers 221 check-in counters.
The Terminal was originally built within the airport's old building to handle 18 million passengers; however, with extreme congestion at the terminal, the airport was forced to expand the terminal to accommodate the opening of 28 remote gates. Over the years, more mobile gates were added to the airport bringing the total as of 2010 to 28. | Dubai International Airport | Wikipedia | 499 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
In 2013, Dubai Airports announced a major renovation for Terminal 1 and Concourse C. The renovations include upgraded baggage systems, replacement of check-in desks and a more spacious departure hall. Arrivals will also see improvements to help reduce waiting times. The renovation was completed by the middle of 2015.
Concourse D
Planning began for further expansion of Dubai Airport, with the construction of Terminal 4, it was revealed on the day Emirates completed its phased operations at the new Terminal 3, on 14 November 2008.
According to Dubai Airport officials, plans for Terminal 4 had begun and extensions would be made to Terminal 3. These are required to bring the capacity of the airport to 80–90 million passengers a year by 2015.
In May 2011, Paul Griffiths, chief executive of Dubai Airports revealed the Dubai Airport masterplan. It involves the construction of Concourse D (previously Terminal 4). With a capacity of 15 million, it would bring the total capacity of the airport to 90 million passengers by 2018—an increase of 15 million. It also will see Emirates take over the operation at Concourse C, along with Concourse A and B which it will already be operating. All remaining airlines will shift to Concourse D, or move to Al Maktoum International Airport. The airport projects that international passenger and cargo traffic will increase at an average annual growth rate of 7.2% and 6.7%, respectively, and that by 2020 passenger numbers at Dubai International Airport will reach 98.5 million and cargo volumes will top 4.1 million tonnes.
Concourse D will have a capacity of 15 million passengers, include 17 gates and will be connected to Terminal 1 via an automated people mover. On 6 February 2016, members of the public were invited to trial the concourse in preparation for its opening. On Wednesday, 24 February 2016, Concourse D officially opened with the first British Airways flight arriving at gate D8.
Concourse D and Terminal 1 reopened on 24 June 2021 following a year's closure due to the COVID-19 pandemic.
Terminal 2
Terminal 2, built in 1998, has an area of and has a capacity of 10 million as of 2013, after several, decent reconstructions and a major expansion in 2012 which saw capacity double. It is used by over 50 airlines, mainly operating in the Persian Gulf region. Most flights operate to India, Saudi Arabia, Iran, Afghanistan and Pakistan.
In June 2009, Terminal 2 became the hub of Air India Express and flydubai, and the terminal houses the airline's corporate head office. | Dubai International Airport | Wikipedia | 505 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Terminal 2 has undergone a major refurbishment recently, extending check-in and boarding facilities, changing the interior and exterior décor, and offering more dining choices to passengers. Capacity was increased to allow for 10 million passengers, an increase of 5 million.
The terminal has now increased the number of facilities available to passengers. Check-in counters have increased to 37. The boarding area is more spacious, with more natural light. Also, the new open boarding gates allow several flights to board simultaneously, improving passenger and aircraft movements. There are a total of 43 remote stands at the terminal. However, passengers cannot move between Terminal 2 to 1 or from 2 to 3 and vice versa inside the airport. They have to make use of Taxi services or public transport available outside.
The Dubai duty-free shopping area covers in departures and in arrivals. The extension included a larger arrivals hall as well.
Terminal 2 has no jetbridges and so passengers are bussed to the aircraft at gates F1-F12.
Terminal 3
The partly underground Terminal 3 was built at a cost of US$4.5 billion, exclusively for Emirates, and has a capacity of 65 million passengers. The terminal has 20 Airbus A380 gates at Concourse A and 5 at Concourse B and 2 at Concourse C. It was announced on 6 September 2012 that Terminal 3 would no longer be Emirates-exclusive, as Emirates and Qantas had set up an extensive code-sharing agreement. Qantas would be the second and only one of two airlines to fly in and out of Terminal 3. This deal also allows Qantas to use the A380 dedicated concourse. Qantas services to and from Dubai ceased in 2018 in favour of a Singapore stopover instead. flydubai, Emirates' low cost subsidiary also currently operates certain selected routes, including most European destinations, to and from Terminal 3.
In March 2023, United began services from Newark to Dubai, operating out of Terminal 3, becoming the only airline other than Emirates and flydubai to currently operate out of the terminal. | Dubai International Airport | Wikipedia | 411 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Upon completion, Terminal 3 was the largest building in the world by floor space, with over of space, capable of handling 60 million passengers in a year. A large part is located under the taxiway area and is directly connected to Concourse B: the departure and arrival halls in the new structure are beneath the airport's apron. Concourse A is connected to the terminal via a Terminal 3 APM. It has been operational since 14 October 2008, and opened in four phases to avoid collapse of baggage handling and other IT systems.
The building includes a multi-level underground structure, first and business class lounges, restaurants, 180 check-in counters, and 2,600 car-parking spaces. The terminal offers more than double the previous retail area of Concourse C, by adding about and Concourse B's of shopping facilities.
In arrivals, the terminal contains 72 immigration counters and 14 baggage carousels. The baggage handling system—the largest system and also the deepest in the world—has a capacity to handle 8,000 bags per hour. The system includes 21 screening injection points, 49 make-up carousels, of conveyor belts capable of handling 15,000 items per hour at a speed of and 4,500 early baggage storage positions.
Concourse A
Concourse A, part of Terminal 3, opened 2 January 2013, has a capacity of 19 million passengers and is connected to the two major public levels of Terminal 3 via Terminal 3 APM in addition to the vehicular and baggage handling system utility tunnels for further transfer. The concourse opened on 2 January 2013 and was built at a cost of US$3.3 billion. The building, which follows the characteristic shape of Concourse B, long, wide and high in the centre from the apron level and accommodates 20 air bridge gates, of which all are capable of handling the Airbus A380-800. There are also 6 remote lounges for passengers departing on flights parked at 13 remote stands. The gates in Concourse A are labeled A1–A24. Gates A6, A7, A18, and A19 are not equipped with jetbridges and so passengers departing from these gates are bussed to the aircraft. | Dubai International Airport | Wikipedia | 437 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
The concourse includes one 4-star hotel and one 5-star hotel, first- and business-class lounges, and duty-free areas. The total built-up area is . The concourse allows for multi-level boarding and boasts the largest first and business class lounges in the world. Each lounge has its own dedicated floor offering direct aircraft access from the lounges. The total amount of retail space at the concourse is , and there is also a total of 14 cafes and restaurants.
The total retail area in the concourse is approximately .
Concourse B
Concourse B is directly connected to terminal 3 and is dedicated exclusively to Emirates. The total built-up area of the concourse itself is . The concourse is long, wide (at midpoint) and high. The terminal has 10 floors (4 basements, a ground floor, and 5 above floors). The building currently includes a multi-level structure for departures and arrivals and includes 32 gates, labeled B1–B32. The concourse has 26 air bridge gates (gates B7-B32) and 5 boarding lounges (B1-B6) for 14 remote stands that are for Airbus A340 and Boeing 777 aircraft only. For transit passengers, the concourse has 3 transfer areas and 62 transfer desks.
The concourse also includes the Emirates first and Business class lounges, and the Marhaba lounge. The First class lounge has a capacity of 1,800 passengers and a total area of . The Business class lounge has a capacity of 3,000 passengers and a total area of . The Marhaba Lounge, the smallest lounge at the concourse has a capacity of 300 passengers at a time.
The total retail area at the concourse is , which also includes 18 restaurants within the food court. There are also three hotels in the concourse; a 5-star hotel and a 4-star hotel.
There is a direct connection to Sheikh Rashid Terminal (Concourse C) located at the control tower structure through passenger walkways. There is also a 300-room hotel and health club including both five and four-star rooms. Concourse B includes five aerobridges that are capable of handling the new Airbus A380. Emirates Airline continues to maintain a presence in Concourse C, operating 12 gates at the concourse as well as the Emirates First Class and Business Class Lounges. | Dubai International Airport | Wikipedia | 468 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Concourse C
Concourse C, a part of Terminal 3, was opened in 2000 and used to be the largest concourse at Dubai International Airport before Concourse B in Terminal 3 opened. It incorporates 50 gates, including 28 air bridges at gates (C1-C23, except for C12a, C15, and C15a) and 22 remote gates located at a lower level of the terminal at gates C29-C50. The gates are labelled C1–C50.
The concourse includes over 17 food and beverage cafes and restaurants, with the food court being located on the Departures Level. Also located in the concourse is a 5-star hotel and a duty-free shopping facility. Other facilities include prayer rooms and a medical center. Concourse C became part of Terminal 3 in 2016 after Concourse D opened.
Al Majlis VIP Pavilion and Dubai Executive Flight Terminal
The Al Majlis VIP pavilion was exclusively built for the Dubai Royal Air Wing and opened on 1 July 2008. The entire facility is a terminal and includes a Royal Majlis and an antenna farm. It also includes eight aircraft hangars with a total built up area of and maintenance hangars for Boeing 747s and Airbus A380s, and a gatehouse for VIP service. In 2010 there were 47,213 customers, 13,162 movements and in 2009, there were a total of 43,968 customers and 14,896 movements.
Executive Flight Services (EFS) caters to those passengers of high class or special importance who travel through Dubai International Airport. It is the largest dedicated business aviation terminal of its kind in the Middle East. It is located at the Dubai Airport Free Zone close to Dubai International's Terminal 2. It only caters to private flights exclusive to the terminal. Airlines operating from the terminal are expected to maintain a lounge. In 2010, EFS handled 7,889 aircraft movements and 25,177 passengers. | Dubai International Airport | Wikipedia | 381 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
The center itself is located close to Terminal 2 and includes a two-story main building, a hangar, a ramp area for aircraft parking and a special VIP car park for long term parking. The center also has its own immigration and customs sections, its own Dubai Duty-Free outlet, a fully equipped business and conference center, eight luxury private lounges, and a limousine service between aircraft and the terminal. The ramp area of the terminal can accommodate up to 22 small-sized private jets, between 8 and 12 medium-sized jets, or up to four large-sized jets such as a Boeing Business Jet (BBJ), the Boeing 727 or the Airbus A319. The facility makes EFC the largest dedicated business aviation terminal in the Middle East.
Cargo Mega Terminal
The cargo village at Dubai International Airport is one of the world's largest and most central cargo hubs, with most of the cargo for Asia and Africa coming through the facility. Forecasts in 2004 for cargo growth predicted that additional major cargo handling facilities were needed to satisfy demands. Plans were put in place to construct the first stage of the cargo mega terminal, which by 2018 will have the ability to handle three million tons of freight. Phase 1 of the cargo mega terminal was completed by 2004 and the next phase of expansion was scheduled for completion in late 2007. Presently the airport has a cargo capacity of 2.5 million tonnes, and will be expanded to handle 3 million.
Flower centre
Dubai Airport has constructed a flower center to handle flower imports and exports, as Dubai is a major hub for the import and export of flowers, and the airport requires a specialist facility since these products need special conditions. The flower center's first phase was completed in 2004 at a cost of $50 million.
The center when completed and functioning will have a floor area of approximately including different export chambers and offices. The handling capacity of the center is expected to be more than 300,000 tonnes of product throughput per annum. The entire facility (with the exception of the offices) will be maintained at an ambient temperature of just .
Runways | Dubai International Airport | Wikipedia | 419 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Dubai Airport has two closely spaced parallel runways, 12R/30L is , 12L/30R is . The gap between the centrelines of the two runways is . The runways are equipped with four sets of ILS to guide landing aircraft safely under very poor weather conditions. The runways were expanded to accommodate the Airbus A380 which came into service in 2007. In 2009, it was announced that the airport installed a Category III landing system, allowing planes to land in low-visibility conditions, such as fog. This system was the first of its kind in the United Arab Emirates.
In 2013 Dubai Airports announced an 80-day runway refurbishment program which started on 1 May 2014 and was completed on 21 July 2014. The northern runway was resurfaced while lighting upgrades and additional taxiways were built on the southern runway to help boost its capacity. The southern runway was closed from 1 to 31 May 2014, while the northern runway was closed from 31 May to 20 July 2014. Due to extra congestion on one runway, all freighter, charter and general aviation flights were diverted to Al Maktoum International Airport. Flights at DXB were reduced by 26% and 14 airlines moved to Al Maktoum International Airport whilst the runways works were being done. Emirates cut 5,000 flights and grounded over 20 aircraft during the period.
Dubai Airport plans to close the southern runway (12R/30L) for complete resurfacing and replacement of the airfield lighting and supporting infrastructure. This will be done during a 45-day period from 16 April 2019 to 30 May 2019. This upgrade will boost safety, service and capacity levels at DXB. Airlines will be required to reduce flight operations at DXB due to single runway operations. | Dubai International Airport | Wikipedia | 350 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Accommodating the Airbus A380
With Dubai-based Emirates being one of the launch customers for the Airbus A380 and also the largest customer, Dubai Airport needed to expand its existing facilities to accommodate the very large aircraft. The Department of Civil Aviation spent $120 million in upgrading both of its terminals and airport infrastructure, including enlarged gate holdrooms, new finger piers, an enlarged runway, new airbridges and extended baggage belt carousels from the normal . Dubai Airport also invested $3.5 billion into a new Concourse A, exclusively for handling Emirates A380s. With the changes made, the airport does not expect embarking and disembarking passengers and baggage from the A380 to take longer than it does for Boeing 747-400s, which carry fewer passengers. On 16 July 2008, Dubai Airport unveiled the first of two specially-built gates capable of handling the aircraft. Costing $10 million, the gates will enable passengers to get on the upper cabin of the new 555-seater aircraft directly from the gate hold rooms. The hold rooms themselves have been enlarged to cater for the larger number of passengers flying the A380s. In addition to the two gates at Terminal 1, five more A380-capable gates were opened at concourse B on 14 October 2008. Concourse A opened on 2 January 2013.
Labor controversy
Workers building a new terminal at Dubai International Airport went on a sympathy strike in March 2006. Another strike took place in October 2007. Four thousand strikers were arrested. Most of them were released some days later and those who were not local were then deported from Dubai.
Airlines and destinations
Passenger
The following airlines offer regular scheduled and charter services to and from Dubai International: | Dubai International Airport | Wikipedia | 343 | 154742 | https://en.wikipedia.org/wiki/Dubai%20International%20Airport | Technology | Asia | null |
Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing inks, fabrics, plastics, paper, sunscreen, food and cosmetics.
Structure and properties
Ilmenite is a heavy (specific gravity 4.7), moderately hard (Mohs hardness 5.6 to 6), opaque black mineral with a submetallic luster. It is almost always massive, with thick tabular crystals being quite rare. It shows no discernible cleavage, breaking instead with a conchoidal to uneven fracture.
Ilmenite crystallizes in the trigonal system with space group R. The ilmenite crystal structure consists of an ordered derivative of the corundum structure; in corundum all cations are identical but in ilmenite Fe2+ and Ti4+ ions occupy alternating layers perpendicular to the trigonal c axis.
Pure ilmenite is paramagnetic (showing only very weak attraction to a magnet), but ilmenite forms solid solutions with hematite that are weakly ferromagnetic and so are noticeably attracted to a magnet. Natural deposits of ilmenite usually contain intergrown or exsolved magnetite that also contribute to its ferromagnetism.
Ilmenite is distinguished from hematite by its less intensely black color and duller appearance and its black streak, and from magnetite by its weaker magnetism.
Discovery
In 1791 William Gregor discovered a deposit of black sand in a stream that runs through the valley just south of the village of Manaccan (Cornwall), and identified for the first time titanium as one of the constituents of the main mineral in the sand. Gregor named this mineral manaccanite. The same mineral was found in the Ilmensky Mountains, near Miass, Russia, and named ilmenite.
Mineral chemistry
Pure ilmenite has the composition . However, ilmenite most often contains appreciable quantities of magnesium and manganese and up to 6 wt% of hematite, , substituting for in the crystal structure. Thus the full chemical formula can be expressed as . Ilmenite forms a solid solution with geikielite () and pyrophanite () which are magnesian and manganiferous end-members of the solid solution series. | Ilmenite | Wikipedia | 508 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Although ilmenite is typically close to the ideal composition, with minor mole percentages of Mn and Mg, the ilmenites of kimberlites usually contain substantial amounts of geikielite molecules, and in some highly differentiated felsic rocks ilmenites may contain significant amounts of pyrophanite molecules.
At temperatures above , there is a complete solid solution between ilmenite and hematite. There is a miscibility gap at lower temperatures, resulting in a coexistence of these two minerals in rocks but no solid solution. This coexistence may result in exsolution lamellae in cooled ilmenites with more iron in the system than can be homogeneously accommodated in the crystal lattice. Ilmenite containing 6 to 13 percent is sometimes described as ferrian ilmenite.
Ilmenite alters or weathers to form the pseudo-mineral leucoxene, a fine-grained yellowish to grayish or brownish material enriched to 70% or more of . Leucoxene is an important source of titanium in heavy mineral sands ore deposits.
Paragenesis
Ilmenite is a common accessory mineral found in metamorphic and igneous rocks. It is found in large concentrations in layered intrusions where it forms as part of a cumulate layer within the intrusion. Ilmenite generally occurs in these cumulates together with orthopyroxene or in combination with plagioclase and apatite (nelsonite).
Magnesian ilmenite is formed in kimberlites as part of the MARID association of minerals (mica-amphibole-rutile-ilmenite-diopside) assemblage of glimmerite xenoliths. Manganiferous ilmenite is found in granitic rocks and also in carbonatite intrusions where it may also contain anomalously high amounts of niobium.
Many mafic igneous rocks contain grains of intergrown magnetite and ilmenite, formed by the oxidation of ulvospinel.
Processing and consumption
Most ilmenite is mined for titanium dioxide production. Ilmenite and titanium dioxide are used in the production of titanium metal. | Ilmenite | Wikipedia | 453 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Titanium dioxide is most used as a white pigment and the major consuming industries for TiO2 pigments are paints and surface coatings, plastics, and paper and paperboard. Per capita consumption of TiO2 in China is about 1.1 kilograms per year, compared with 2.7 kilograms for Western Europe and the United States.
Titanium is the ninth most abundant element on Earth and represents about 0.6 percent of the Earth's crust. Ilmenite is commonly processed to obtain a titanium concentrate, which is called "synthetic rutile" if it contains more than 90 percent TiO2, or more generally "titaniferous slags" if it has a lower TiO2 content. More than 80 percent of the estimated global production of titanium concentrate is obtained from the processing of ilmenite, while 13 percent is obtained from titaniferous slags and 5 percent from rutile.
Ilmenite can be converted into pigment grade titanium dioxide via either the sulfate process or the chloride process. Ilmenite can also be improved and purified to titanium dioxide in the form of rutile using the Becher process.
Ilmenite ores can also be converted to liquid iron and a titanium-rich slag using a smelting process.
Ilmenite ore is used as a flux by steelmakers to line blast furnace hearth refractory.
Ilmenite can be used to produce ferrotitanium via an aluminothermic reduction.
Feedstock production
Most ilmenite is recovered from heavy mineral sands ore deposits, where the mineral is concentrated as a placer deposit and weathering reduces its iron content, increasing the percentage of titanium. However, ilmenite can also be recovered from "hard rock" titanium ore sources, such as ultramafic to mafic layered intrusions or anorthosite massifs. The ilmenite in layered intrusions is sometimes abundant, but it contains considerable intergrowths of magnetite that reduce its ore grade. Ilmenite from anorthosite massifs often contain large amounts of calcium or magnesium that render it unsuitable for the chloride process.
The proven reserves of ilmenite and rutile ore are estimated at between 423 and 600 million tonnes titanium dioxide. The largest ilmenite deposits are in South Africa, India, the United States, Canada, Norway, Australia, Ukraine, Russia and Kazakhstan. Additional deposits are found in Bangladesh, Chile, Mexico and New Zealand. | Ilmenite | Wikipedia | 495 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Australia was the world's largest ilmenite ore producer in 2011, with about 1.3 million tonnes of production, followed by South Africa, Canada, Mozambique, India, China, Vietnam, Ukraine, Norway, Madagascar and United States.
The top four ilmenite and rutile feedstock producers in 2010 were Rio Tinto Group, Iluka Resources, Exxaro and Kenmare Resources, which collectively accounted for more than 60% of world's supplies.
The world's two largest open cast ilmenite mines are:
The Tellnes mine located in Sokndal, Norway, and run by Titania AS (owned by Kronos Worldwide Inc.) with 0.55 Mtpa capacity and 57 Mt contained reserves.
The Rio Tinto Group's Lac Tio mine located near Havre Saint-Pierre, Quebec in Canada with a 3 Mtpa capacity and 52 Mt reserves.
Major mineral sands based ilmenite mining operations include:
Richards Bay Minerals in South Africa, majority-owned by the Rio Tinto Group.
Kenmare Resources' Moma mine in Mozambique.
Iluka Resources' mining operations in Australia including Murray Basin, Eneabba and Capel.
The Kerala Minerals & Metals Ltd (KMML), Indian Rare Earths (IRE), VV Mineral mines in India.
TiZir Ltd.'s Grande Cote mine in Senegal
QIT Madagascar Minerals mine, majority-owned by the Rio Tinto Group, which began production in 2009 and is expected to produce 0.75 Mtpa of ilmenite, potentially expanding to 2 Mtpa in future phases. | Ilmenite | Wikipedia | 325 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Attractive major potential ilmenite deposits include:
The Karhujupukka magnetite-ilmenite deposit in Kolari, northern Finland with around 5 Mt reserves and ore containing about 6.2% titanium.
The Balla Balla magnetite-iron-titanium-vanadium ore deposit in the Pilbara of Western Australia, which contains 456 million tonnes of cumulate ore horizon grading 45% , 13.7% and 0.64% , one of the richest magnetite-ilmenite ore bodies in Australia
The Coburn, WIM 50, Douglas, Pooncarie mineral sands deposits in Australia.
The Magpie titano-magnetite (iron-titanium-vanadium-chrome) deposits in eastern Quebec of Canada with about 1 billion tonnes containing about 43% Fe, 12% TiO2, 0.4% V2O5, and 2.2% Cr2O3.
The Longnose deposit in Northeast Minnesota is considered to be "the largest and richest ilmenite deposit in North America."
In 2020, China has by far the highest titanium mining activity. About 35 percent of the world’s ilmenite is mined in China, representing 33 percent of total titanium mineral mining (including ilmenite and rutile). South Africa and Mozambique are also important contributors, representing 13 percent and 12 percent of worldwide ilmenite mining, respectively. Australia represents 6 percent of the total ilmenite mining and 31 percent of rutile mining. Sierra Leone and Ukraine are also big contributors to rutile mining.
China is the biggest producer of titanium dioxide, followed by the United States and Germany. China is also the leader in the production of titanium metal, but Japan, the Russian Federation and Kazakhstan have emerged as important contributors to this field.
Patenting activities | Ilmenite | Wikipedia | 369 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Patenting activity related to titanium dioxide production from ilmenite is rapidly increasing. Between 2002 and 2022, there have been 459 patent families that describe the production of titanium dioxide from ilmenite, and this number is growing rapidly. The majority of these patents describe pre-treatment processes, such as using smelting and magnetic separation to increase titanium concentration in low-grade ores, leading to titanium concentrates or slags. Other patents describe processes to obtain titanium dioxide, either by a direct hydrometallurgical process or through two industrially exploited processes, the sulfate process and the chloride process. Acid leaching might be used either as a pre-treatment or as part of a hydrometallurgical process to directly obtain titanium dioxide or synthetic rutile (>90 percent titanium dioxide, TiO2). The sulfate process represents 40 percent of the world’s titanium dioxide production and is protected in 23 percent of patent families. The chloride process is only mentioned in 8 percent of patent families, although it provides 60 percent of the worldwide industrial production of titanium dioxide.Key contributors to patents on the production of titanium dioxide are companies from China, Australia and the United States, reflecting the major contribution of these countries to industrial production. Chinese companies Pangang and Lomon Billions Groups are the main contributors and hold diversified patent portfolios covering both pre-treatment and the processes leading to a final product.
In comparison, patenting activity related to titanium metal production from ilmenite remains stable. Between 2002 and 2022, there have been 92 patent families that describe the production of titanium metal from ilmenite, and this number has remained quite steady. These patents describe the production of titanium metal starting from mineral ores, such as ilmenite, and from titanium dioxide (TiO2) and titanium tetrachloride (TiCl4), a chemical obtained as an intermediate in the chloride process. The starting materials are purified if needed, and then converted to titanium metal by a chemical reduction process using a reducing agent. Processes mainly differ in regard to the reducing agent used to transform the starting material into titanium metal: magnesium is the most frequently cited reducing agent and the most exploited in industrial production.Key players in the field are Japanese companies, in particular Toho Titanium and Osaka Titanium Technologies, both focusing on reduction using magnesium. Pangang also contributes to titanium metal production and holds patents describing reduction by molten salt electrolysis. | Ilmenite | Wikipedia | 491 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Lunar ilmenite
Ilmenite has been found in lunar samples, particularly in high-Ti lunar mare basalts common from Apollo 11 and Apollo 17 sites, and on average, constitutes up to 5% of lunar meteorites. Ilmenite has been targeted for ISRU water and oxygen extraction due to a simplistic reduction reaction which occurs with CO and H2 buffers.
Sources | Ilmenite | Wikipedia | 78 | 154744 | https://en.wikipedia.org/wiki/Ilmenite | Physical sciences | Minerals | Earth science |
Zirconium dioxide (), sometimes known as zirconia (not to be confused with zirconium silicate or zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone and a diamond simulant.
Production, chemical properties, occurrence
Zirconia is produced by calcining zirconium compounds, exploiting its high thermostability.
Structure
Three phases are known: monoclinic below 1170 °C, tetragonal between 1170 °C and 2370 °C, and cubic above 2370 °C. The trend is for higher symmetry at higher temperatures, as is usually the case. A small percentage of the oxides of calcium or yttrium stabilize in the cubic phase. The very rare mineral tazheranite, , is cubic. Unlike , which features six-coordinated titanium in all phases, monoclinic zirconia consists of seven-coordinated zirconium centres. This difference is attributed to the larger size of the zirconium atom relative to the titanium atom.
Chemical reactions
Zirconia is chemically unreactive. It is slowly attacked by concentrated hydrofluoric acid and sulfuric acid. When heated with carbon, it converts to zirconium carbide. When heated with carbon in the presence of chlorine, it converts to zirconium(IV) chloride. This conversion is the basis for the purification of zirconium metal and is analogous to the Kroll process.
Engineering properties
Zirconium dioxide is one of the most studied ceramic materials. adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The change of volume caused by the structure transitions from tetragonal to monoclinic to cubic induces large stresses, causing it to crack upon cooling from high temperatures. When the zirconia is blended with some other oxides, the tetragonal and/or cubic phases are stabilized. Effective dopants include magnesium oxide (MgO), yttrium oxide (, yttria), calcium oxide (), and cerium(III) oxide (). | Zirconium dioxide | Wikipedia | 499 | 154750 | https://en.wikipedia.org/wiki/Zirconium%20dioxide | Physical sciences | Oxide salts | Chemistry |
Zirconia is often more useful in its phase 'stabilized' state. Upon heating, zirconia undergoes disruptive phase changes. By adding small percentages of yttria, these phase changes are eliminated, and the resulting material has superior thermal, mechanical, and electrical properties. In some cases, the tetragonal phase can be metastable. If sufficient quantities of the metastable tetragonal phase is present, then an applied stress, magnified by the stress concentration at a crack tip, can cause the tetragonal phase to convert to monoclinic, with the associated volume expansion. This phase transformation can then put the crack into compression, retarding its growth, and enhancing the fracture toughness. This mechanism, known as transformation toughening, significantly extends the reliability and lifetime of products made with stabilized zirconia.
The band gap is dependent on the phase (cubic, tetragonal, monoclinic, or amorphous) and preparation methods, with typical estimates from 5–7 eV.
A special case of zirconia is that of tetragonal zirconia polycrystal, or TZP, which is indicative of polycrystalline zirconia composed of only the metastable tetragonal phase.
Uses
The main use of zirconia is in the production of hard ceramics, such as in dentistry, with other uses including as a protective coating on particles of titanium dioxide pigments, as a refractory material, in insulation, abrasives, and enamels.
Stabilized zirconia is used in oxygen sensors and fuel cell membranes because it has the ability to allow oxygen ions to move freely through the crystal structure at high temperatures. This high ionic conductivity (and a low electronic conductivity) makes it one of the most useful electroceramics. Zirconium dioxide is also used as the solid electrolyte in electrochromic devices.
Zirconia is a precursor to the electroceramic lead zirconate titanate (PZT), which is a high-κ dielectric, which is found in myriad components. | Zirconium dioxide | Wikipedia | 443 | 154750 | https://en.wikipedia.org/wiki/Zirconium%20dioxide | Physical sciences | Oxide salts | Chemistry |
Niche uses
The very low thermal conductivity of cubic phase of zirconia also has led to its use as a thermal barrier coating, or TBC, in jet and diesel engines to allow operation at higher temperatures. Thermodynamically, the higher the operation temperature of an engine, the greater the possible efficiency. Another low-thermal-conductivity use is as a ceramic fiber insulation for crystal growth furnaces, fuel-cell stacks, and infrared heating systems.
This material is also used in dentistry in the manufacture of subframes for the construction of dental restorations such as crowns and bridges, which are then veneered with a conventional feldspathic porcelain for aesthetic reasons, or of strong, extremely durable dental prostheses constructed entirely from monolithic zirconia, with limited but constantly improving aesthetics. Zirconia stabilized with yttria (yttrium oxide), known as yttria-stabilized zirconia, can be used as a strong base material in some full ceramic crown restorations.
Transformation-toughened zirconia is used to make ceramic knives. Because of the hardness, ceramic-edged cutlery stays sharp longer than steel edged products.
Due to its infusibility and brilliant luminosity when incandescent, it was used as an ingredient of sticks for limelight.
Zirconia has been proposed to electrolyze carbon monoxide and oxygen from the atmosphere of Mars to provide both fuel and oxidizer that could be used as a store of chemical energy for use with surface transportation on Mars. Carbon monoxide/oxygen engines have been suggested for early surface transportation use, as both carbon monoxide and oxygen can be straightforwardly produced by zirconia electrolysis without requiring use of any of the Martian water resources to obtain hydrogen, which would be needed for the production of methane or any hydrogen-based fuels.
Zirconia can be used as photocatalyst since its high band gap (~ 5 eV) allows the generation of high-energy electrons and holes. Some studies demonstrated the activity of doped zirconia (in order to increase visible light absorption) in degrading organic compounds and reducing Cr(VI) from wastewaters.
Zirconia is also a potential high-κ dielectric material with potential applications as an insulator in transistors. | Zirconium dioxide | Wikipedia | 482 | 154750 | https://en.wikipedia.org/wiki/Zirconium%20dioxide | Physical sciences | Oxide salts | Chemistry |
Zirconia is also employed in the deposition of optical coatings; it is a high-index material usable from the near-UV to the mid-IR, due to its low absorption in this spectral region. In such applications, it is typically deposited by PVD.
In jewelry making, some watch cases are advertised as being "black zirconium oxide". In 2015 Omega released a fully watch named "The Dark Side of The Moon" with ceramic case, bezel, pushers, and clasp, advertising it as four times harder than stainless steel and therefore much more resistant to scratches during everyday use.
In gas tungsten arc welding, tungsten electrodes containing 1% zirconium oxide (a.k.a. zirconia) instead of 2% thorium have good arc starting and current capacity, and are not radioactive.
Diamond simulant
Single crystals of the cubic phase of zirconia are commonly used as diamond simulant in jewellery. Like diamond, cubic zirconia has a cubic crystal structure and a high index of refraction. Visually discerning a good quality cubic zirconia gem from a diamond is difficult, and most jewellers will have a thermal conductivity tester to identify cubic zirconia by its low thermal conductivity (diamond is a very good thermal conductor). This state of zirconia is commonly called cubic zirconia, CZ, or zircon by jewellers, but the last name is not chemically accurate. Zircon is actually the mineral name for naturally occurring zirconium(IV) silicate (). | Zirconium dioxide | Wikipedia | 337 | 154750 | https://en.wikipedia.org/wiki/Zirconium%20dioxide | Physical sciences | Oxide salts | Chemistry |
In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds free water intake. This is usually due to excessive sweating, disease, or a lack of access to water. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers.
Most people can tolerate a 3-4% decrease in total body water without difficulty or adverse health effects. A 5-8% decrease can cause fatigue and dizziness. Loss of over 10% of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs with a 15 and 25% loss of body water. Mild dehydration usually resolves with oral rehydration, but severe cases may need intravenous fluids.
Dehydration can cause hypernatremia (high levels of sodium ions in the blood). This is distinct from hypovolemia (loss of blood volume, particularly blood plasma).
Chronic dehydration can cause kidney stones as well as the development of chronic kidney disease.
Signs and symptoms
The hallmarks of dehydration include thirst and neurological changes such as headaches, general discomfort, loss of appetite, nausea, decreased urine volume (unless polyuria is the cause of dehydration), confusion, unexplained tiredness, purple fingernails, and seizures. The symptoms of dehydration become increasingly severe with greater total body water loss. A body water loss of 1-2%, considered mild dehydration, is shown to impair cognitive performance. While in people over age 50, the body's thirst sensation diminishes with age, a study found that there was no difference in fluid intake between young and old people. Many older people have symptoms of dehydration, with the most common being fatigue. Dehydration contributes to morbidity in the elderly population, especially during conditions that promote insensible free water losses, such as hot weather.
Cause
Risk factors for dehydration include but are not limited to: exerting oneself in hot and humid weather, habitation at high altitudes, endurance athletics, elderly adults, infants, children and people living with chronic illnesses.
Dehydration can also come as a side effect from many different types of drugs and medications. | Dehydration | Wikipedia | 488 | 155056 | https://en.wikipedia.org/wiki/Dehydration | Biology and health sciences | Specific diseases | Health |
In the elderly, blunted response to thirst or inadequate ability to access free water in the face of excess free water losses (especially hyperglycemia related) seem to be the main causes of dehydration. Excess free water or hypotonic water can leave the body in two ways – sensible loss such as osmotic diuresis, sweating, vomiting and diarrhea, and insensible water loss, occurring mainly through the skin and respiratory tract. In humans, dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body. These occur primarily through either impaired thirst/water access or sodium excess.
Mechanism
Water makes up approximately 60% of the human body by mass. Within the body, water is classified as intracellular fluid or extracellular fluid. Intracellular fluid refers to water that is contained within the cells. This consists of approximately 40% of the total body water. Fluid inside the cells has high concentrations of potassium, magnesium, phosphate, and proteins. Extracellular fluid consists of all fluid outside of the cells, and it includes blood and interstitial fluid. This makes up approximately 60% of the total body water. The most common ions in extracellular fluid include sodium, chloride, and bicarbonate.
The concentration of dissolved molecules and ions in the fluid is described as Osmolarity and is measured in osmoles per liter (Osm/L). When the body experiences a free water deficit, the concentration of solutes is increased. This leads to a higher serum osmolarity. When serum osmolarity is elevated, this is detected by osmoreceptors in the hypothalamus. These receptors trigger the release of antidiuretic hormone (ADH). ADH resists dehydration by increasing water absorption in the kidneys and constricting blood vessels. It acts on the V2 receptors in the cells of the collecting tubule of the nephron to increase expression of aquaporin. In more extreme cases of low blood pressure, the hypothalamus releases higher amounts of ADH which also acts on V1 receptors. These receptors cause contractions in the peripheral vascular smooth muscle. This increases systemic vascular resistance and raises blood pressure.
Diagnosis | Dehydration | Wikipedia | 470 | 155056 | https://en.wikipedia.org/wiki/Dehydration | Biology and health sciences | Specific diseases | Health |
Definition
Dehydration occurs when water intake does not replace free water lost due to normal physiologic processes, including breathing, urination, perspiration, or other causes, including diarrhea, and vomiting. Dehydration can be life-threatening when severe and lead to seizures or respiratory arrest, and also carries the risk of osmotic cerebral edema if rehydration is overly rapid.
The term "dehydration" has sometimes been used incorrectly as a proxy for the separate, related condition of hypovolemia, which specifically refers to a decrease in volume of blood plasma. The two are regulated through independent mechanisms in humans; the distinction is important in guiding treatment.
Physical examination
Common exam findings of dehydration include dry mucous membranes, dry axillae, increased capillary refill time, sunken eyes, and poor skin turgor. More extreme cases of dehydration can lead to orthostatic hypotension, dizziness, weakness, and altered mental status. Depending on the underlying cause of dehydration, other symptoms may be present as well. Excessive sweating from exercise may be associated with muscle cramps. Patients with gastrointestinal water loss from vomiting or diarrhea may also have fever or other systemic signs of infection.
The skin turgor test can be used to support the diagnosis of dehydration. The skin turgor test is conducted by pinching skin on the patient's body, in a location such as the forearm or the back of the hand, and watching to see how quickly it returns to its normal position. The skin turgor test can be unreliable in patients who have reduced skin elasticity, such as the elderly. | Dehydration | Wikipedia | 361 | 155056 | https://en.wikipedia.org/wiki/Dehydration | Biology and health sciences | Specific diseases | Health |
Laboratory tests
While there is no single gold standard test to diagnose dehydration, evidence can be seen in multiple laboratory tests involving blood and urine. Serum osmolarity above 295 mOsm/kg is typically seen in dehydration due to free water loss. A urinalysis, which is a test that performs chemical and microscopic analysis of urine, may find darker color or foul odor with severe dehydration. Urinary sodium also provides information about the type of dehydration. For hyponatremic dehydration, such as from vomiting or diarrhea, urinary sodium will be less than 10mmol/L due to increased sodium retention by the kidneys in an effort to conserve water. In dehydrated patients with sodium loss due to diuretics or renal dysfunction, urinary sodium may be elevated above 20 mmol/L. Patients may also have elevated serum levels of blood urea nitrogen (BUN) and creatinine. Both of these molecules are normally excreted by the kidney, but when the circulating blood volume is low, the kidney can become injured. This causes decreased kidney function and results in elevated BUN and creatinine in the serum.
Prevention
For routine activities, thirst is normally an adequate guide to maintain proper hydration. Minimum water intake will vary individually depending on weight, energy expenditure, age, sex, physical activity, environment, diet, and genetics. With exercise, exposure to hot environments, or a decreased thirst response, additional water may be required. In athletes in competition, drinking to thirst optimizes performance and safety, despite weight loss, and as of 2010, there was no scientific study showing that it is beneficial to stay ahead of thirst and maintain weight during exercise.
In warm or humid weather, or during heavy exertion, water loss can increase markedly, because humans have a large and widely variable capacity for sweating. Whole-body sweat losses in men can exceed 2 L/h during competitive sport, with rates of 3–4 L/h observed during short-duration, high-intensity exercise in the heat. When such large amounts of water are being lost through perspiration, electrolytes, especially sodium, are also being lost. | Dehydration | Wikipedia | 461 | 155056 | https://en.wikipedia.org/wiki/Dehydration | Biology and health sciences | Specific diseases | Health |
In most athletes exercising and sweating for 4–5 hours with a sweat sodium concentration of less than 50 mmol/L, the total sodium lost is less than 10% of total body stores (total stores are approximately 2,500 mmol, or 58 g for a 70-kg person). These losses appear to be well tolerated by most people. The inclusion of sodium in fluid replacement drinks has some theoretical benefits and poses little or no risk, so long as these fluids are hypotonic (since the mainstay of dehydration prevention is the replacement of free water losses).
Treatment
The most effective treatment for minor dehydration is widely considered to be drinking water and reducing fluid loss. Plain water restores only the volume of the blood plasma, inhibiting the thirst mechanism before solute levels can be replenished. Consumption of solid foods can also contribute to hydration. It is estimated approximately 22% of American water intake comes from food. Urine concentration and frequency will return to normal as dehydration resolves.
In some cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (through oral rehydration therapy, or fluid replacement by intravenous therapy). As oral rehydration is less painful, non-invasive, inexpensive, and easier to provide, it is the treatment of choice for mild dehydration. Solutions used for intravenous rehydration may be isotonic,hypertonic, or hypotonic depending on the cause of dehydration as well as the sodium concentration in the blood. Pure water injected into the veins will cause the breakdown (lysis) of red blood cells (erythrocytes).
When fresh water is unavailable (e.g. at sea or in a desert), seawater or drinks with significant alcohol concentration will worsen dehydration. Urine contains a lower solute concentration than seawater; this requires the kidneys to create more urine to remove the excess salt, causing more water to be lost than was consumed from seawater. If a person is dehydrated and taken to a medical facility, IVs can also be used. | Dehydration | Wikipedia | 453 | 155056 | https://en.wikipedia.org/wiki/Dehydration | Biology and health sciences | Specific diseases | Health |
For severe cases of dehydration where fainting, unconsciousness, or other severely inhibiting symptoms are present (the patient is incapable of standing upright or thinking clearly), emergency attention is required. Fluids containing a proper balance of replacement electrolytes are given orally or intravenously with continuing assessment of electrolyte status; complete resolution is normal in all but the most extreme cases.
Prognosis
The prognosis for dehydration depends on the cause and extent of dehydration. Mild dehydration normally resolves with oral hydration. Chronic dehydration, such as from physically demanding jobs or decreased thirst, can lead to chronic kidney disease. Elderly people with dehydration are at higher risk of confusion, urinary tract infections, falls, and even delayed wound healing. In children with mild to moderate dehydration, oral hydration is adequate for a full recovery. | Dehydration | Wikipedia | 189 | 155056 | https://en.wikipedia.org/wiki/Dehydration | Biology and health sciences | Specific diseases | Health |
Pubic hair (or pubes , ) is terminal body hair that is found in the genital area and pubic region of adolescent and adult humans. The hair is located on and around the sex organs, and sometimes at the top of the inside of the thighs, even extending down the perineum, and to the anal region. Pubic hair is also found on the scrotum and base of the penile shaft (in males) and on the vulva (in females). Around the pubis bone and the mons pubis that covers it, it is known as a pubic patch, which can be styled.
Although fine vellus hair is present in the area during childhood, pubic hair is considered to be the heavier, longer, coarser hair that develops during puberty as an effect of rising levels of hormones: androgens in males and estrogens in females. Pubic hair differs from other hair on the body, and is a secondary sex characteristic.
Many cultures regard pubic hair as erotic, and most cultures associate it with the genitals, which people are expected to keep covered at all times. In some cultures, it is the norm for pubic hair to be removed, especially of females; the practice is regarded as part of personal hygiene. In some cultures, the exposure of pubic hair (for example, when wearing a swimsuit) may be regarded as unaesthetic or embarrassing, and is therefore trimmed (or otherwise styled) to avoid it being visible.
Development
Pubic hair forms in response to the increasing levels of testosterone in both girls and boys. Those hair follicles that are located and stimulated in androgen sensitive areas develop pubic hair. The Tanner scale describes and quantifies the development of pubic hair. Before the onset of puberty, the genital area of both boys and girls has very fine vellus hair (stage 1). At the onset of puberty, the body produces rising levels of the sex hormones, and in response, the skin of the genital area begins to produce thicker and rougher, often curlier, hair with a faster growth rate. The onset of pubic hair development is termed pubarche.
In females, pubarche is usually the second sign of puberty after thelarche, though sometimes it happens before thelarche. | Pubic hair | Wikipedia | 475 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
In males, the first pubic hair appears as a few sparse hairs that are usually thin on the scrotum or at the upper base of the penis (stage 2). Within a year, hairs around the base of the penis are abundant (stage 3). Within 3 to 4 years, hair fills the pubic area (stage 4) and becomes much thicker and darker, and by 5 years extends to the near thighs and upwards on the abdomen toward the umbilicus (stage 5).
Other areas of the skin are similarly, though slightly less, sensitive to androgens and androgenic hair typically appears somewhat later. In rough sequence of sensitivity to androgens and appearance of androgenic hair are the armpits (axillae), perianal area, upper lip, preauricular areas (sideburns), periareolar areas (nipples), middle of the chest, neck under the chin, remainder of chest and beard area, limbs and shoulders, back, and buttocks. Although generally considered part of the process of puberty, pubarche is distinct and independent of the process of maturation of the gonads that leads to sexual maturation and fertility. Pubic hair can develop from adrenal androgens alone and can develop even when the ovaries or testes are defective and nonfunctional. There is little, if any, difference in the capacity of male and female bodies to grow hair in response to androgens.
Pubic hair and underarm hair can vary in color considerably from the hair of the scalp. In most people, it is darker, although it can also be lighter. In most cases it is most similar in color to a person's eyebrows.
Hair texture varies from tightly curled to entirely straight, not necessarily correlating to the texture of the scalp hair. People of East Asian heritage tend to have black, wavy pubic hair.
Pubic hair patterns can vary by race and ethnicity. Patterns of pubic hair, known as the escutcheon, vary between both the sexes and individuals. On most females, the pubic patch is triangular and lies over the vulva and mons pubis. On many males, the pubic patch tapers upwards to a line of hair pointing towards the navel (see abdominal hair), roughly a more upward-pointing triangle. As with axillary (armpit) hair, pubic hair is associated with a concentration of sebaceous glands in the area. | Pubic hair | Wikipedia | 511 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
Clinical significance
Pubic lice
Pubic hair can become infested with pubic lice (also known as crab lice). Adult pubic lice are in length. The pubic hair can usually host up to a dozen on average. Pubic lice are usually found attached to hair in the pubic area but sometimes are found on coarse hair elsewhere on the body (for example, eyebrows, eyelashes, beard, mustache, chest, armpits, etc.). Crab lice attach to pubic hair that is thicker than other body hair because their claws are adapted to the specific diameter of pubic hair. Pubic lice infestations (pthiriasis) are usually spread through sexual contact.
The crab louse can travel up to 10 inches on the body. Pubic lice infestation is found worldwide and occurs in all races and ethnic groups and in all economic levels. Pubic lice are usually spread through sexual contact and are most common in adults. Occasionally pubic lice may be spread by close personal contact or contact with articles such as clothing, bed linens, and towels that have been used by an infested person. Pubic lice found on the head or eyelashes of children may be an indication of sexual exposure or abuse. Pubic lice do not transmit disease; however, secondary bacterial infection can occur from scratching of the skin. They are much broader in comparison to head and body lice. Adults are found only on the human host and require human blood to survive. If adults are forced off the host, they will die within 48 hours without a blood feeding. | Pubic hair | Wikipedia | 331 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
Symptoms of a crab louse infection in the pubic area is intense itching, redness and inflammation. These symptoms cause increased circulation to the skin of the pubic region creating a blood-rich environment for the crab louse. Pubic lice infestation can also be diagnosed by identifying the presence of nits or eggs on the pubic hair. In December 2016 NPR reported that "Frequent removal of pubic hair is associated with an increased risk for herpes, syphilis and human papillomavirus". However, the medical community has also seen a recent increase in folliculitis, or infection around the hair follicle, in women who wax or shave their bikini areas. Some of these infections can develop into more serious abscesses that require incision with a scalpel, drainage of the abscess, and antibiotics. Staphylococcus aureus is the most common cause of folliculitis. Burns can result when depilatory wax is used, even according to manufacturer instructions.
Grooming risks
Pubic hair grooming has been associated with injury and infection. It is estimated that about one quarter of the people who groom their pubic hair have had at least one lifetime injury because of the practice. Grooming has also been associated with cutaneous sexually transmitted infections, such as genital warts, syphilis, and herpes.
Society and culture | Pubic hair | Wikipedia | 288 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
According to John Ruskin's biographer Mary Lutyens, the notable author, artist, and art critic was apparently accustomed only to the hairless nudes portrayed unrealistically in art, never having seen a naked woman before his wedding night. He was allegedly so shocked by his discovery of his wife Effie's pubic hair that he rejected her, and the marriage was later legally annulled. He is supposed to have thought his wife was freakish and deformed. Later writers have often followed Lutyens and repeated this version of events. For example, Gene Weingarten, writing in his book I'm with Stupid (2004) states that "Ruskin had [the marriage] annulled because he was horrified to behold upon his bride a thatch of hair, rough and wild, similar to a man's. He thought her a monster." However, there is no proof for this, and some disagree. Peter Fuller in his book Theoria: Art and the Absence of Grace writes, "It has been said that he was frightened on the wedding night by the sight of his wife's pubic hair; more probably, he was perturbed by her menstrual blood." Ruskin's biographers Tim Hilton and John Batchelor also believe that menstruation is the more likely explanation.
At puberty, many girls find the sudden sprouting of pubic hair disturbing, and sometimes as unclean, because in many cases young girls have been screened by their family and by society from the sight of pubic hair. Young boys, on the other hand, tend not to be similarly disturbed by the development of their pubic hair, usually having seen body hair on their fathers.
With the reintroduction of public beaches and pools, bathing in Western Europe and the Mediterranean early in the 20th century, exposure of both sexes' areas near their pubic hair became more common, and after the progressive reduction in the size of female and male swimsuits, especially since the coming into fashion and growth in popularity of the bikini after the 1940s, the practice of shaving or bikini waxing of pubic hair off the hem lines also came into vogue.
Grooming practices | Pubic hair | Wikipedia | 455 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
In some Middle Eastern societies, removal of male and female body hair has been considered proper hygiene, mandated by local customs, for many centuries. Muslim teaching (applicable to males and females) includes Islamic hygienical jurisprudence in which pubic and armpit hair must be pulled out or shaven to be considered as Sunnah. Trimming is taught to be considered acceptable.
Women working in pornography typically remove their pubic hair by shaving, a practice that became fashionable in the late 20th century. Shaving is used rather than bikini waxing because it can be performed daily, whereas waxing requires several days of growth before it can be repeated. According to feminist writer Caitlin Moran, the reason for the removal of pubic hair from women in pornography was a matter of "technical considerations of cinematography". Hair removal progressed to full removal. Because of the popularity of pornography, pubic hair shaving was mimicked by women, and it is among women outside the pornography industry that waxing became common in the late 20th and 21st century.
The presentation is regarded by some as being erotic and aesthetic, while others consider the style as unnatural. Some people remove pubic hairs for erotic and sexual reasons or because they or their sex partner enjoy the feel of a hairless crotch.
According to one academic study, as of 2016, approximately 50% of men in the United States practice regular pubic hair grooming, which can include trimming, shaving and removal. The study found that the prevalence of grooming decreases with age. Of males who groom pubic hair, 87% groom the hair above the penis, 66% groom the scrotum and 57% groom the penile shaft.
Methods
All hair can be removed with wax formulated for that purpose. Some individuals may remove part or all of their pubic hair, axillary hair and facial hair. Pubic hair removal using wax is called bikini waxing. The method of removing hair is called depilation (when removing only the hair above the skin) or epilation (when removing the entire hair). Beauty salons often offer various waxing services. It is sometimes referred to as "pubic topiary". Sugaring, an alternative to waxing, uses a sugar-based paste, which may include lemon, rather than wax. Sugaring removes fewer skin cells than waxing. Other methods of hair removal include laser hair removal and electrolysis. | Pubic hair | Wikipedia | 487 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
Some women modify their pubic hair, either to fit in with societal trends or as an expression of their own style or lifestyle. Styles of pubic hair modification include:
Triangle or American wax (pubic hair is shortened from the sides to form a triangle so that pubic hair is hidden while wearing swimwear. The triangle can range from the very edge of the "bikini line" to up to an inch reduction on either side. Remaining hair length can be from an inch and a half to half an inch);
Landing strip/French wax (pubic hair removed except for a strip of hair extending from the abdomen to the vulva);
Partial Brazilian wax (pubic hair fully removed except for a small triangular strip);
Full Brazilian wax or "sphinx" (complete removal of pubic hair); and
Freestyle.
There are variations of the Brazilian wax in which a design is formed out of the pubic hair. Stencils for several shapes are available commercially. A controversial Gucci commercial included female pubic hair shaved into a 'G'.
Sexual attraction
A woman or man's decision to grow or shave their pubic hair can play a role in attracting a partner. A Cosmopolitan study found that a plurality of respondents, both male and female, preferred partners who shave or at least trim their pubic hair. A smaller percentage of 6% of men and 10% of women preferred their partners to go natural and not shave or trim their pubic hair.
In art
In ancient Egyptian art, female pubic hair is indicated in the form of painted triangles. In medieval and classical European art, pubic hair was very rarely depicted, and male pubic hair was often, but not always, omitted. Sometimes it was portrayed in stylized form, as was the case with Greek graphic art.
In 16th century southern Europe, Michelangelo showed the male David with stylized pubic hair, but female bodies were depicted hairless below the head. Nevertheless, Michelangelo's male nudes on the Sistine Chapel ceiling display no pubic hair. | Pubic hair | Wikipedia | 410 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
In the late 18th century, female pubic hair was openly portrayed in Japanese shunga (erotica), especially in the ukiyo-e tradition. Hokusai's picture The Dream of the Fisherman's Wife (1814), which depicts a woman having an erotic fantasy, is a well-known example. In Japanese drawings, such as hentai, pubic hair is often omitted, since for a long time the display of pubic hair was not legal. The interpretation of the law has since changed.
(1866), by the French artist Gustave Courbet, was controversial for its realism, which pushed the limits of what was considered presentable at the time. In contrast to academic painting, which favored smooth, idealized nudes, this painting showed a close-up view of the vulva, with full pubic hair, of a woman lying on a bed with legs spread.
In fashion
In 1985, four weeks before his death, Rudi Gernreich unveiled the pubikini, a topless bathing suit that exposed the wearer's mons pubis and pubic hair. It was a thin, V-shaped, thong-style bottom that in the front featured a tiny strip of fabric that exposed the wearer's pubic hair. The pubikini was described as a pièce de résistance totally freeing the human body.
In history
Evidence of pubic hair removal in ancient India is thought to date back to 4000 to 3000 BC. According to ethnologist F. Fawcett, writing in 1901, he had observed the removal of body hair, including pubic hair about the vulva, as a custom of women from the Hindu Nair caste. | Pubic hair | Wikipedia | 344 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
In Western societies, after the spread of Christianity, public exposure of a woman's bare skin between the ankle and waist started to be disapproved of culturally. Upper body exposure due to the use of the popular vest bodices used in Western Europe from the 15th century to early 20th century, as the widespread dirndls used even in more traditionally conservative mountain areas and the more or less loose shirts under these, enabled a permissive view of the shoulders, décolletage and arms allowing a free exposure of upper body hair in women of all classes with less rejection or discrimination than body hair on the sex organs, obviously to conceal by implication. Many people came to consider public exposure of pubic hair to be embarrassing. It may be regarded as immodest and sometimes as obscene. However, it never came to have a full hold in Western culture in wide tracts of Central Europe, until the encroaching of Protestantism during the 16th century on formerly more tolerant customs.
In the 1450s, British prostitutes shaved their pubic hair for purposes of personal hygiene and the combatting of pubic lice and would don merkins (or pubic wigs) when their line of work required it.
Among the British upper classes during the Georgian era, pubic hair from one's lover was frequently collected as a souvenir. The curls were, for instance, worn like cockades in men's hats as potency talismans or exchanged among lovers as tokens of affection. The museum of St. Andrews University in Scotland has in its collection a snuffbox full of pubic hair of one of King George IV's mistresses (possibly Elizabeth Conyngham), which the notoriously licentious monarch donated to the Fife sex club, The Beggar's Benison.
In literature
In the erotic novel My Secret Life the narrator "Walter", an evident connoisseur of female pubic hair, talks with clear delight of a fine bush of a Scotswoman's thick red pubic hair:
The bush was long and thick, twisting and curling in masses half-way up to her navel, and it spread about up her buttocks, gradually getting shorter there. | Pubic hair | Wikipedia | 451 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
In another part of his autobiography Walter remarks that he has seen those "bare of hair, those with but hairy stubble, those with bushes six inches long, covering them from bum bone to navel." And he adds reflectively – "there is not much that I have not seen, felt or tried, with respect to this supreme female article."
In like vein, in The Memoirs of Dolly Morton, an American erotic classic, the attributes of Miss Dean are noted with some surprise – her spot was covered with a "thick forest of glossy dark brown hair," with locks nearly two inches long. One man remarked:
But Gosh! I've never seen such a fleece between a woman's legs in my life. Darn me if she wouldn't have to be sheared before man could get into her. | Pubic hair | Wikipedia | 168 | 155117 | https://en.wikipedia.org/wiki/Pubic%20hair | Biology and health sciences | Integumentary system | Biology |
Bruxism is excessive teeth grinding or jaw clenching. It is an oral parafunctional activity; i.e., it is unrelated to normal function such as eating or talking. Bruxism is a common behavior; the global prevalence of bruxism (both sleep and awake) is 22.22%. Several symptoms are commonly associated with bruxism, including aching jaw muscles, headaches, hypersensitive teeth, tooth wear, and damage to dental restorations (e.g. crowns and fillings). Symptoms may be minimal, without patient awareness of the condition. If nothing is done, after a while many teeth start wearing down until the whole tooth is gone.
There are two main types of bruxism: one occurs during sleep (nocturnal bruxism) and one during wakefulness (awake bruxism). Dental damage may be similar in both types, but the symptoms of sleep bruxism tend to be worse on waking and improve during the course of the day, and the symptoms of awake bruxism may not be present at all on waking, and then worsen over the day.
The causes of bruxism are not completely understood, but probably involve multiple factors. Awake bruxism is more common in women, whereas men and women are affected in equal proportions by sleep bruxism. Awake bruxism is thought to have different causes from sleep bruxism. Several treatments are in use, although there is little evidence of robust efficacy for any particular treatment.
Epidemiology
There is a wide variation in reported epidemiologic data for bruxism, and this is largely due to differences in the definition, diagnosis and research methodologies of these studies. E.g. several studies use self-reported bruxism as a measure of bruxism, and since many people with bruxism are not aware of their habit, self-reported tooth grinding and clenching habits may be a poor measure of the true prevalence.
The ICSD-R states that 85–90% of the general population grind their teeth to a degree at some point during their life, although only 5% will develop a clinical condition. Some studies have reported that awake bruxism affects females more commonly than males, while in sleep bruxism, males and females are affected equally. | Bruxism | Wikipedia | 471 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Children are reported to brux as commonly as adults. It is possible for sleep bruxism to occur as early as the first year of life, after the first teeth (deciduous incisors) erupt into the mouth, and the overall prevalence in children is about 14–20%. The ICSD-R states that sleep bruxism may occur in over 50% of normal infants. Often sleep bruxism develops during adolescence, and the prevalence in 18- to 29-year-olds is about 13%. The overall prevalence in adults is reported to be 8%, and people over the age of 60 are less likely to be affected, with the prevalence dropping to about 3% in this group.
According to a meta-analysis conducted in 2024, the global prevalence of bruxism (both sleep and awake) is 22.22%. The global prevalence of sleep bruxism is 21%, while the prevalence of awake bruxism is 23%. The occurrence of sleep bruxism, based on polysomnography, was estimated at 43%. The highest prevalence of sleep bruxism was observed in North America at 31%, followed by South America at 23%, Europe at 21%, and Asia at 19%. The prevalence of awake bruxism was highest in South America at 30%, followed by Asia at 25% and Europe at 18%. The review also concluded that overall, bruxism affects males and females equally, and affects elderly people less commonly.
Signs and symptoms
Most people who brux are unaware of the problem, either because there are no symptoms, or because the symptoms are not understood to be associated with a clenching and grinding problem. The symptoms of sleep bruxism are usually most intense immediately after waking, and then slowly abate, and the symptoms of a grinding habit which occurs mainly while awake tend to worsen through the day, and may not be present on waking. Bruxism may cause a variety of signs and symptoms, including: | Bruxism | Wikipedia | 407 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
A grinding or tapping noise during sleep, sometimes detected by a partner or a parent. This noise can be surprisingly loud and unpleasant, and can wake a sleeping partner. Noises are rarely associated with awake bruxism.
Other parafunctional activity which may occur together with bruxism: cheek biting (which may manifest as morsicatio buccarum or linea alba), or lip biting.
A burning sensation on the tongue (see: glossodynia), possibly related to a coexistent "tongue thrusting" parafunctional activity.
Indentations of the teeth in the tongue ("crenated tongue" or "scalloped tongue").
Hypertrophy of the muscles of mastication (increase in the size of the muscles that move the jaw), particularly the masseter muscle.
Tenderness, pain or fatigue of the muscles of mastication, which may get worse during chewing or other jaw movement.
Trismus (restricted mouth opening).
Pain or tenderness of the temporomandibular joints, which may manifest as preauricular pain (in front of the ear), or pain referred to the ear (otalgia).
Clicking of the temporomandibular joints.
Headaches, particularly pain in the temples, caused by muscle pain associated with the temporalis muscle.
Excessive tooth wear, particularly attrition, which flattens the occlusal (biting) surface, but also possibly other types of tooth wear such as abfraction, where notches form around the neck of the teeth at the gumline.
Tooth fractures, and repeated failure of dental restorations (fillings, crowns, etc.).
Hypersensitive teeth, (e.g. dental pain when drinking a cold liquid) caused by wearing away of the thickness of insulating layers of dentin and enamel around the dental pulp.
Inflammation of the periodontal ligament of teeth, which may make them sore to bite on, and possibly also a degree of loosening of the teeth. | Bruxism | Wikipedia | 413 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Bruxism is usually detected because of the effects of the process (most commonly tooth wear and pain), rather than the process itself. The large forces that can be generated during bruxism can have detrimental effects on the components of masticatory system, namely the teeth, the periodontium and the articulation of the mandible with the skull (the temporomandibular joints). The muscles of mastication that act to move the jaw can also be affected since they are being utilized over and above of normal function. | Bruxism | Wikipedia | 110 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Pain
Most people with bruxism will experience no pain. The presence or degree of pain does not necessarily correlate with the severity of grinding or clenching. The pain in the muscles of mastication caused by bruxism can be likened to muscle pain after exercise. The pain may be felt over the angle of the jaw (masseter) or in the temple (temporalis), and may be described as a headache or an aching jaw. Most (but not all) bruxism includes clenching force provided by masseter and temporalis muscle groups; but some bruxers clench and grind front teeth only, which involves minimal action of the masseter and temporalis muscles. The temporomandibular joints themselves may also become painful, which is usually felt just in front of the ear, or inside the ear itself. Clicking of the jaw joint may also develop. The forces exerted on the teeth are more than the periodontal ligament is biologically designed to handle, and so inflammation may result. A tooth may become sore to bite on, and further, tooth wear may reduce the insulating width of enamel and dentin that protects the pulp of the tooth and result in hypersensitivity, e.g. to cold stimuli.
The relationship of bruxism with temporomandibular joint dysfunction (TMD, or temporomandibular pain dysfunction syndrome) is debated. Many suggest that sleep bruxism can be a causative or contributory factor to pain symptoms in TMD. Indeed, the symptoms of TMD overlap with those of bruxism. Others suggest that there is no strong association between TMD and bruxism. A systematic review investigating the possible relationship concluded that when self-reported bruxism is used to diagnose bruxism, there is a positive association with TMD pain, and when stricter diagnostic criteria for bruxism are used, the association with TMD symptoms is much lower. In severe, chronic cases, bruxism can lead to myofascial pain and arthritis of the temporomandibular joints. | Bruxism | Wikipedia | 425 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Tooth wear
Many publications list tooth wear as a consequence of bruxism, but some report a lack of a positive relationship between tooth wear and bruxism. Tooth wear caused by tooth-to-tooth contact is termed attrition. This is the most usual type of tooth wear that occurs in bruxism, and affects the occlusal surface (the biting surface) of the teeth. The exact location and pattern of attrition depends on how the bruxism occurs, e.g., when the canines and incisors of the opposing arches are moved against each other laterally, by the action of the medial pterygoid muscles, this can lead to the wearing down of the incisal edges of the teeth. To grind the front teeth, most people need to posture their mandible forwards, unless there is an existing edge to edge, class III incisal relationship. People with bruxism may also grind their posterior teeth (back teeth), which wears down the cusps of the occlusal surface. Once tooth wear progresses through the enamel layer, the exposed dentin layer is softer and more vulnerable to wear and tooth decay. If enough of the tooth is worn away or decayed, the tooth will effectively be weakened, and may fracture under the increased forces that occur in bruxism.
Abfraction is another type of tooth wear that is postulated to occur with bruxism, although some still argue whether this type of tooth wear is a reality. Abfraction cavities are said to occur usually on the facial aspect of teeth, in the cervical region as V-shaped defects caused by flexing of the tooth under occlusal forces. It is argued that similar lesions can be caused by long-term forceful toothbrushing. However, the fact that the cavities are V-shaped does not suggest that the damage is caused by toothbrush abrasion, and that some abfraction cavities occur below the level of the gumline, i.e., in an area shielded from toothbrush abrasion, supports the validity of this mechanism of tooth wear. In addition to attrition, erosion is said to synergistically contribute to tooth wear in some bruxists, according to some sources. | Bruxism | Wikipedia | 470 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Tooth mobility
The view that occlusal trauma (as may occur during bruxism) is a causative factor in gingivitis and periodontitis is not widely accepted. It is thought that the periodontal ligament may respond to increased occlusal (biting) forces by resorbing some of the bone of the alveolar crest, which may result in increased tooth mobility, however these changes are reversible if the occlusal force is reduced. Tooth movement that occurs during occlusal loading is sometimes termed fremitus. It is generally accepted that increased occlusal forces are able to increase the rate of progression of pre-existing periodontal disease (gum disease), however the main stay treatment is plaque control rather than elaborate occlusal adjustments. It is also generally accepted that periodontal disease is a far more common cause of tooth mobility and pathological tooth migration than any influence of bruxism, although bruxism may much less commonly be involved in both.
Causes
The muscles of mastication (the temporalis muscle, masseter muscle, medial pterygoid muscle and lateral pterygoid muscle) are paired on either side and work together to move the mandible, which hinges and slides around its dual articulation with the skull at the temporomandibular joints. Some of the muscles work to elevate the mandible (close the mouth), and others also are involved in lateral (side to side), protrusive or retractive movements. Mastication (chewing) is a complex neuromuscular activity that can be controlled either by subconscious processes or by conscious processes. In individuals without bruxism or other parafunctional activities, during wakefulness the jaw is generally at rest and the teeth are not in contact, except while speaking, swallowing or chewing. It is estimated that the teeth are in contact for less than 20 minutes per day, mostly during chewing and swallowing. Normally during sleep, the voluntary muscles are inactive due to physiologic motor paralysis, and the jaw is usually open.
Ankyloglossia is suspected as a cause of bruxism. | Bruxism | Wikipedia | 449 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Some bruxism activity is rhythmic with bite force pulses of tenths of a second (like chewing), and some have longer bite force pulses of 1 to 30 seconds (clenching). Some individuals clench without significant lateral movements. Bruxism can also be regarded as a disorder of repetitive, unconscious contraction of muscles. This typically involves the masseter muscle and the anterior portion of the temporalis (the large outer muscles that clench), and the lateral pterygoids, relatively small bilateral muscles that act together to perform sideways grinding.
Multiple causes
The cause of bruxism is largely unknown, but it is generally accepted to have multiple possible causes. Bruxism is a parafunctional activity, but it is debated whether this represents a subconscious habit or is entirely involuntary. The relative importance of the various identified possible causative factors is also debated.
Awake bruxism is thought to be usually semivoluntary, and often associated with stress caused by family responsibilities or work pressures. Some suggest that in children, bruxism may occasionally represent a response to earache or teething. Awake bruxism usually involves clenching (sometimes the term "awake clenching" is used instead of awake bruxism), but also possibly grinding, and is often associated with other semivoluntary oral habits such as cheek biting, nail biting, chewing on a pen or pencil absent mindedly, or tongue thrusting (where the tongue is pushed against the front teeth forcefully). | Bruxism | Wikipedia | 297 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
There is evidence that sleep bruxism is caused by mechanisms related to the central nervous system, involving sleep arousal and neurotransmitter abnormalities. Underlying these factors may be psychosocial factors including daytime stress which is disrupting peaceful sleep. Sleep bruxism is mainly characterized by "rhythmic masticatory muscle activity" (RMMA) at a frequency of about once per second, and also with occasional tooth grinding. It has been shown that the majority (86%) of sleep bruxism episodes occur during periods of sleep arousal. One study reported that sleep arousals which were experimentally induced with sensory stimulation in sleeping bruxists triggered episodes of sleep bruxism. Sleep arousals are a sudden change in the depth of the sleep stage, and may also be accompanied by increased heart rate, respiratory changes and muscular activity, such as leg movements. Initial reports have suggested that episodes of sleep bruxism may be accompanied by gastroesophageal reflux, decreased esophageal pH (acidity), swallowing, and decreased salivary flow. Another report suggested a link between episodes of sleep bruxism and a supine sleeping position (lying face up).
Disturbance of the dopaminergic system in the central nervous system has also been suggested to be involved in the etiology of bruxism. Evidence for this comes from observations of the modifying effect of medications which alter dopamine release on bruxing activity, such as levodopa, amphetamines or nicotine. Nicotine stimulates release of dopamine, which is postulated to explain why bruxism is twice as common in smokers compared to non-smokers. | Bruxism | Wikipedia | 345 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Historical focus
Historically, many believed that problems with the bite were the sole cause for bruxism. It was often claimed that a person would grind at the interfering area in a subconscious, instinctive attempt to wear this down and "self equiliberate" their occlusion. However, occlusal interferences are extremely common and usually do not cause any problems. It is unclear whether people with bruxism tend to notice problems with the bite because of their clenching and grinding habit, or whether these act as a causative factor in the development of the condition. In sleep bruxism especially, there is no evidence that removal of occlusal interferences has any impact on the condition. People with no teeth at all who wear dentures can still have bruxism, although dentures also often change the original bite. Most modern sources state that there is no relationship, or at most a minimal relationship, between bruxism and occlusal factors. The findings of one study, which used self-reported tooth grinding rather than clinical examination to detect bruxism, suggested that there may be more of a relationship between occlusal factors and bruxism in children. However, the role of occlusal factors in bruxism cannot be completely discounted due to insufficient evidence and problems with the design of studies. A minority of researchers continue to claim that various adjustments to the mechanics of the bite are capable of curing bruxism (see Occlusal adjustment/reorganization). | Bruxism | Wikipedia | 310 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Psychosocial factors
Many studies have reported significant psychosocial risk factors for bruxism, particularly a stressful lifestyle, and this evidence is growing, but still not conclusive. Some consider emotional stress and anxiety to be the main triggering factors. It has been reported that persons with bruxism respond differently to depression, hostility and stress compared to people without bruxism. Stress has a stronger relationship to awake bruxism, but the role of stress in sleep bruxism is less clear, with some stating that there is no evidence for a relationship with sleep bruxism. However, children with sleep bruxism have been shown to have greater levels of anxiety than other children. People aged 50 with bruxism are more likely to be single and have a high level of education. Work-related stress and irregular work shifts may also be involved. Personality traits are also commonly discussed in publications concerning the causes of bruxism, e.g. aggressive, competitive or hyperactive personality types. Some suggest that suppressed anger or frustration can contribute to bruxism. Stressful periods such as examinations, family bereavement, marriage, divorce, or relocation have been suggested to intensify bruxism. Awake bruxism often occurs during periods of concentration such as while working at a computer, driving or reading. Animal studies have also suggested a link between bruxism and psychosocial factors. Rosales et al. electrically shocked lab rats, and then observed high levels of bruxism-like muscular activity in rats that were allowed to watch this treatment compared to rats that did not see it. They proposed that the rats who witnessed the electrical shocking of other rats were under emotional stress which may have caused the bruxism-like behavior.
Genetic factors
Some research suggests that there may be a degree of inherited susceptibility to develop sleep bruxism. 21–50% of people with sleep bruxism have a direct family member who had sleep bruxism during childhood, suggesting that there are genetic factors involved, although no genetic markers have yet been identified. Offspring of people who have sleep bruxism are more likely to also have sleep bruxism than children of people who do not have bruxism, or people with awake bruxism rather than sleep bruxism. | Bruxism | Wikipedia | 466 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Medications
Certain stimulant drugs, including both prescribed and recreational drugs, are thought by some to cause the development of bruxism. However, others argue that there is insufficient evidence to draw such a conclusion. Examples may include dopamine agonists, dopamine antagonists, tricyclic antidepressants, selective serotonin reuptake inhibitors, alcohol, cocaine, and amphetamines (including those taken for medical reasons). In some reported cases where bruxism is thought to have been initiated by selective serotonin reuptake inhibitors, decreasing the dose resolved the side effect. Other sources state that reports of selective serotonin reuptake inhibitors causing bruxism are rare, or only occur with long-term use.
Specific examples include levodopa (when used in the long term, as in Parkinson's disease), fluoxetine, metoclopramide, lithium, cocaine, venlafaxine, citalopram, fluvoxamine, methylenedioxyamphetamine (MDA), methylphenidate (used in attention deficit hyperactive disorder), and gamma-hydroxybutyric acid (GHB) and similar gamma-aminobutyric acid-inducing analogues such as phenibut. Bruxism can also be exacerbated by excessive consumption of caffeine, as in coffee, tea or chocolate. Bruxism has also been reported to occur commonly comorbid with drug addiction. Methylenedioxymethamphetamine (MDMA, ecstasy) has been reported to be associated with bruxism, which occurs immediately after taking the drug and for several days afterwards. Tooth wear in people who take ecstasy is also frequently much more severe than in people with bruxism not associated with ecstasy. | Bruxism | Wikipedia | 378 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Occlusal factors
Occlusion is defined most simply as "contacts between teeth", and is the meeting of teeth during biting and chewing. The term does not imply any disease. Malocclusion is a medical term referring to less than ideal positioning of the upper teeth relative to the lower teeth, which can occur both when the upper jaw is ideally proportioned to the lower jaw, or where there is a discrepancy between the size of the upper jaw relative to the lower jaw. Malocclusion of some sort is so common that the concept of an "ideal occlusion" is called into question, and it can be considered "normal to be abnormal". An occlusal interference may refer to a problem which interferes with the normal path of the bite, and is usually used to describe a localized problem with the position or shape of a single tooth or group of teeth. A premature contact is one part of the bite meeting sooner than other parts, meaning that the rest of the teeth meet later or are held open, e.g., a new dental restoration on a tooth (e.g., a crown) which has a slightly different shape or position to the original tooth may contact too soon in the bite. A deflective contact/interference is an interference with the bite that changes the normal path of the bite. A common example of a deflective interference is an over-erupted upper wisdom tooth, often because the lower wisdom tooth has been removed or is impacted. In this example, when the jaws are brought together, the lower back teeth contact the prominent upper wisdom tooth before the other teeth, and the lower jaw has to move forward to allow the rest of the teeth to meet. The difference between a premature contact and a deflective interference is that the latter implies a dynamic abnormality in the bite.
Possible associations
Several associations between bruxism and other conditions, usually neurological or psychiatric disorders, have rarely been reported, with varying degrees of evidence (often in the form of case reports). Examples include: | Bruxism | Wikipedia | 417 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Acrodynia
Atypical facial pain
Autism
Cerebral palsy
Disturbed sleep patterns and other sleep disorders, such as obstructive sleep apnea, snoring, moderate daytime sleepiness, and insomnia
Down syndrome
Dyskinesias
Epilepsy
Eustachian tube dysfunction
Infarction in the basal ganglia
Intellectual disability, particularly in children
Leigh disease
Meningococcal septicaemia
Multiple system atrophy
Oromandibular dystonia
Parkinson's diseases, (possibly due to long-term therapy with levodopa causing dopaminergic dysfunction)
Rett syndrome
Torus mandibularis and buccal exostosis
Trauma, e.g. brain injury or coma
Diagnosis
Early diagnosis of bruxism is advantageous, but difficult. Early diagnosis can prevent damage that may be incurred and the detrimental effect on quality of life. A diagnosis of bruxism is usually made clinically, and is mainly based on the person's history (e.g. reports of grinding noises) and the presence of typical signs and symptoms, including tooth mobility, tooth wear, masseteric hypertrophy, indentations on the tongue, hypersensitive teeth (which may be misdiagnosed as reversible pulpitis), pain in the muscles of mastication, and clicking or locking of the temporomandibular joints. Questionnaires can be used to screen for bruxism in both the clinical and research settings.
For tooth grinders who live in a household with other people, diagnosis of grinding is straightforward: Housemates or family members would advise a bruxer of recurrent grinding. Grinders who live alone can likewise resort to a sound-activated tape recorder. To confirm the condition of clenching, on the other hand, bruxers may rely on such devices as the Bruxchecker, Bruxcore, or a beeswax-bearing biteplate. | Bruxism | Wikipedia | 394 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
The Individual (personal) Tooth-Wear Index was developed to objectively quantify the degree of tooth wear in an individual, without being affected by the number of missing teeth. Bruxism is not the only cause of tooth wear. Another possible cause of tooth wear is acid erosion, which may occur in people who drink a lot of acidic liquids such as concentrated fruit juice, or in people who frequently vomit or regurgitate stomach acid, which itself can occur for various reasons. People also demonstrate a normal level of tooth wear, associated with normal function. The presence of tooth wear only indicates that it had occurred at some point in the past, and does not necessarily indicate that the loss of tooth substance is ongoing. People who clench and perform minimal grinding will also not show much tooth wear. Occlusal splints are usually employed as a treatment for bruxism, but they can also be of diagnostic use, e.g. to observe the presence or absence of wear on the splint after a certain period of wearing it at night.
The most usual trigger in sleep bruxism that leads a person to seek medical or dental advice is being informed by a sleeping partner of unpleasant grinding noises during sleep. The diagnosis of sleep bruxism is usually straightforward, and involves the exclusion of dental diseases, temporomandibular disorders, and the rhythmic jaw movements that occur with seizure disorders (e.g. epilepsy). This usually involves a dental examination, and possibly electroencephalography if a seizure disorder is suspected. Polysomnography shows increased masseter and temporalis muscular activity during sleep. Polysomnography may involve electroencephalography, electromyography, electrocardiography, air flow monitoring and audio–video recording. It may be useful to help exclude other sleep disorders; however, due to the expense of the use of a sleep lab, polysomnography is mostly of relevance to research rather than routine clinical diagnosis of bruxism.
Tooth wear may be brought to the person's attention during routine dental examination. With awake bruxism, most people will often initially deny clenching and grinding because they are unaware of the habit. Often, the person may re-attend soon after the first visit and report that they have now become aware of such a habit. | Bruxism | Wikipedia | 467 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Several devices have been developed that aim to objectively measure bruxism activity, either in terms of muscular activity or bite forces. They have been criticized for introducing a possible change in the bruxing habit, whether increasing or decreasing it, and are therefore poorly representative to the native bruxing activity. These are mostly of relevance to research, and are rarely used in the routine clinical diagnosis of bruxism. Examples include the "Bruxcore Bruxism-Monitoring Device" (BBMD, "Bruxcore Plate"), the "intra-splint force detector" (ISFD), and electromyographic devices to measure masseter or temporalis muscle activity (e.g. the "BiteStrip", and the "Grindcare").
ICSD-R diagnostic criteria
The ICSD-R listed diagnostic criteria for sleep bruxism. The minimal criteria include both of the following:
A. symptom of tooth-grinding or tooth-clenching during sleep, and
B. One or more of the following:
Abnormal tooth wear
Grinding sounds
Discomfort of the jaw muscles
With the following criteria supporting the diagnosis:
C. polysomnography shows both:
Activity of jaw muscles during sleep
No associated epileptic activity
D. No other medical or mental disorders (e.g., sleep-related epilepsy, which may cause abnormal movement during sleep).
E. The presence of other sleep disorders (e.g., obstructive sleep apnea syndrome).
Definition examples
Bruxism is derived from the Greek word (brykein) "to bite, or to gnash, grind the teeth". People with bruxism are called bruxists or bruxers and the verb itself is "to brux". There is no widely accepted definition of bruxism. Examples of definitions include:
Classification by temporal pattern | Bruxism | Wikipedia | 382 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Bruxism can be subdivided into two types based upon when the parafunctional activity occurs – during sleep ("sleep bruxism"), or while awake ("awake bruxism"). This is the most widely used classification since sleep bruxism generally has different causes to awake bruxism, although the effects on the condition on the teeth may be the same. The treatment is also often dependent upon whether the bruxism happens during sleep or while awake, e.g., an occlusal splint worn during sleep in a person who only bruxes when awake will probably have no benefit. Some have even suggested that sleep bruxism is an entirely different disorder and is not associated with awake bruxism. Awake bruxism is sometimes abbreviated to AB, and is also termed "diurnal bruxism", DB, or "daytime bruxing". Sleep bruxism is sometimes abbreviated to SB, and is also termed "sleep-related bruxism", "nocturnal bruxism", or "nocturnal tooth grinding". According to the International Classification of Sleep Disorders revised edition (ICSD-R), the term "sleep bruxism" is the most appropriate since this type occurs during sleep specifically rather than being associated with a particular time of day, i.e., if a person with sleep bruxism were to sleep during the day and stay awake at night then the condition would not occur during the night but during the day. The ICDS-R defined sleep bruxism as "a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep", classifying it as a parasomnia. The second edition (ICSD-2) however reclassified bruxism to a "sleep related movement disorder" rather than a parasomnia. | Bruxism | Wikipedia | 378 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Classification by cause
Alternatively, bruxism can be divided into primary bruxism (also termed "idiopathic bruxism"), where the disorder is not related to any other medical condition, or secondary bruxism, where the disorder is associated with other medical conditions. Secondary bruxism includes iatrogenic causes, such as the side effect of prescribed medications. Another source divides the causes of bruxism into three groups, namely central or pathophysiological factors, psychosocial factors and peripheral factors. The World Health Organization's International Classification of Diseases 10th revision does not have an entry called bruxism, instead listing "tooth grinding" under somatoform disorders. To describe bruxism as a purely somatoform disorder does not reflect the mainstream, modern view of this condition (see causes).
Classification by severity
The ICSD-R described three different severities of sleep bruxism, defining mild as occurring less than nightly, with no damage to teeth or psychosocial impairment; moderate as occurring nightly, with mild impairment of psychosocial functioning; and severe as occurring nightly, and with damage to the teeth, temporomandibular disorders and other physical injuries, and severe psychosocial impairment.
Classification by duration
The ICSD-R also described three different types of sleep bruxism according to the duration the condition is present, namely acute, which lasts for less than one week; subacute, which lasts for more than a week and less than one month; and chronic which lasts for over a month.
Management
Treatment for bruxism revolves around repairing the damage to teeth that has already occurred, and also often, via one or more of several available methods, attempting to prevent further damage and manage symptoms, but there is no widely accepted, best treatment. Since bruxism is not life-threatening, and there is little evidence of the efficacy of any treatment, it has been recommended that only conservative treatment which is reversible and that carries low risk of morbidity should be used. The main treatments that have been described in awake and sleep bruxism are described below. | Bruxism | Wikipedia | 437 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Psychosocial interventions
Given the strong association between awake bruxism and psychosocial factors (the relationship between sleep bruxism and psychosocial factors being unclear), the role of psychosocial interventions could be argued to be central to the management. The most simple form of treatment is therefore reassurance that the condition does not represent a serious disease, which may act to alleviate contributing stress.
Sleep hygiene education should be provided by the clinician, as well as a clear and short explanation of bruxism (definition, causes and treatment options). Relaxation and tension-reduction have not been found to reduce bruxism symptoms, but have given patients a sense of well-being. One study has reported less grinding and reduction of EMG activity after hypnotherapy.
Other interventions include relaxation techniques, stress management, behavioural modification, habit reversal and hypnosis (self hypnosis or with a hypnotherapist). Cognitive behavioral therapy has been recommended by some for treatment of bruxism. In many cases awake bruxism can be reduced by using reminder techniques. Combined with a protocol sheet this can also help to evaluate in which situations bruxism is most prevalent.
Medication
Many different medications have been used to treat bruxism, including benzodiazepines, anticonvulsants, beta blockers, dopamine agents, antidepressants, muscle relaxants, and others. However, there is little, if any, evidence for their respective and comparative efficacies with each other and when compared to a placebo. A multiyear systematic review to investigate the evidence for drug treatments in sleep bruxism published in 2014 (Pharmacotherapy for Sleep Bruxism. Macedo, et al.) found "insufficient evidence on the effectiveness of pharmacotherapy for the treatment of sleep bruxism." | Bruxism | Wikipedia | 384 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Specific drugs that have been studied in sleep bruxism are clonazepam, levodopa, amitriptyline, bromocriptine, pergolide, clonidine, propranolol, and l-tryptophan, with some showing no effect and others appear to have promising initial results; however, it has been suggested that further safety testing is required before any evidence-based clinical recommendations can be made. When bruxism is related to the use of selective serotonin reuptake inhibitors in depression, adding buspirone has been reported to resolve the side effect. Tricyclic antidepressants have also been suggested to be preferable to selective serotonin reuptake inhibitors in people with bruxism, and may help with the pain.
Prevention of dental damage
Bruxism can cause significant tooth wear if it is severe, and sometimes dental restorations (crowns, fillings etc.) are damaged or lost, sometimes repeatedly. Most dentists therefore prefer to keep dental treatment in people with bruxism very simple and only carry it out when essential, since any dental work is likely to fail in the long term. Dental implants, dental ceramics such as Emax crowns and complex bridgework for example are relatively contraindicated in bruxists. In the case of crowns, the strength of the restoration becomes more important, sometimes at the cost of aesthetic considerations. E.g. a full coverage gold crown, which has a degree of flexibility and also involves less removal (and therefore less weakening) of the underlying natural tooth may be more appropriate than other types of crown which are primarily designed for esthetics rather than durability. Porcelain veneers on the incisors are particularly vulnerable to damage, and sometimes a crown can be perforated by occlusal wear. | Bruxism | Wikipedia | 375 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Occlusal splints (also termed dental guards) are commonly prescribed, mainly by dentists and dental specialists, as a treatment for bruxism. Proponents of their use claim many benefits, however when the evidence is critically examined in systematic reviews of the topic, it is reported that there is insufficient evidence to show that occlusal splints are effective for sleep bruxism as well as bruxism overall.
Furthermore, occlusal splints are probably ineffective for awake bruxism, since they tend to be worn only during sleep. However, occlusal splints may be of some benefit in reducing the tooth wear that may accompany bruxism, but by mechanically protecting the teeth rather than reducing the bruxing activity itself. In a minority of cases, sleep bruxism may be made worse by an occlusal splint. Some patients will periodically return with splints with holes worn through them, either because the bruxism is aggravated, or unaffected by the presence of the splint. When tooth-to-tooth contact is possible through the holes in a splint, it is offering no protection against tooth wear and needs to be replaced.
Occlusal splints are divided into partial or full-coverage splints according to whether they fit over some or all of the teeth. They are typically made of plastic (e.g. acrylic) and can be hard or soft. A lower appliance can be worn alone, or in combination with an upper appliance. Usually lower splints are better tolerated in people with a sensitive gag reflex. Another problem with wearing a splint can be stimulation of salivary flow, and for this reason some advise to start wearing the splint about 30 mins before going to bed so this does not lead to difficulty falling asleep. As an added measure for hypersensitive teeth in bruxism, desensitizing toothpastes (e.g. containing strontium chloride) can be applied initially inside the splint so the material is in contact with the teeth all night. This can be continued until there is only a normal level of sensitivity from the teeth, although it should be remembered that sensitivity to thermal stimuli is also a symptom of pulpitis, and may indicate the presence of tooth decay rather than merely hypersensitive teeth. | Bruxism | Wikipedia | 493 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Splints may also reduce muscle strain by allowing the upper and lower jaw to move easily with respect to each other. Treatment goals include: constraining the bruxing pattern to avoid damage to the temporomandibular joints; stabilizing the occlusion by minimizing gradual changes to the positions of the teeth, preventing tooth damage and revealing the extent and patterns of bruxism through examination of the markings on the splint's surface. A dental guard is typically worn during every night's sleep on a long-term basis. However, a meta-analysis of occlusal splints (dental guards) used for this purpose concluded "There is not enough evidence to state that the occlusal splint is effective for treating sleep bruxism."
A repositioning splint is designed to change the patient's occlusion, or bite. The efficacy of such devices is debated. Some writers propose that irreversible complications can result from the long-term use of mouthguards and repositioning splints. Random controlled trials with these type devices generally show no benefit over other therapies.
Another partial splint is the nociceptive trigeminal inhibition tension suppression system (NTI-TSS) dental guard. This splint snaps onto the front teeth only. It is theorized to prevent tissue damages primarily by reducing the bite force from attempts to close the jaw normally into a forward twisting of the lower front teeth. The intent is for the brain to interpret the nerve sensations as undesirable, automatically and subconsciously reducing clenching force. However, there may be potential for the NTI-TSS device to act as a Dahl appliance, holding the posterior teeth out of occlusion and leading to their over-eruption, deranging the occlusion (i.e. it may cause the teeth to move position). This is far more likely if the appliance is worn for excessive periods of time, which is why NTI type appliances are designed for night time use only, and ongoing follow-ups are recommended.
A mandibular advancement device (normally used for treatment of obstructive sleep apnea) may reduce sleep bruxism, although its use may be associated with discomfort. | Bruxism | Wikipedia | 474 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Botulinum toxin
Botulinum neurotoxin (BoNT) is used as a treatment for bruxism. A 2020 overview of systematic reviews found that botulinum toxin type A (BTX-A) showed a significant pain and sleep bruxism frequency reduction when compared to placebo or conventional treatment (behavioral therapy, occlusal splints, and drugs), after 6 and 12 months.
Botulinum toxin causes muscle paralysis/atrophy by inhibition of acetylcholine release at neuromuscular junctions. BoNT injections are used in bruxism on the theory that a dilute solution of the toxin will partially paralyze the muscles and lessen their ability to forcefully clench and grind the jaw, while aiming to retain enough muscular function to enable normal activities such as talking and eating. This treatment typically involves five or six injections into the masseter and temporalis muscles, and less often into the lateral pterygoids (given the possible risk of decreasing the ability to swallow) taking a few minutes per side. The effects may be noticeable by the next day, and they may last for about three months. Occasionally, adverse effects may occur, such as bruising, but this is quite rare. The dose of toxin used depends upon the person, and a higher dose may be needed in people with stronger muscles of mastication. With the temporary and partial muscle paralysis, atrophy of disuse may occur, meaning that the future required dose may be smaller or the length of time the effects last may be increased.
Biofeedback
Biofeedback is a process or device that allows an individual to become aware of, and alter physiological activity with the aim of improving health. Although the evidence of biofeedback has not been tested for awake bruxism, there is recent evidence for the efficacy of biofeedback in the management of nocturnal bruxism in small control groups. Electromyographic monitoring devices of the associated muscle groups tied with automatic alerting during periods of clenching and grinding have been prescribed for awake bruxism. Dental appliances with capsules that break and release a taste stimulus when enough force is applied have also been described in sleep bruxism, which would wake the person from sleep in an attempt to prevent bruxism episodes. "Large scale, double-blind, experiment confirming the effectiveness of this approach have yet to be carried out." | Bruxism | Wikipedia | 493 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Occlusal adjustment/reorganization
As an alternative to simply reactively repairing the damage to teeth and conforming to the existing occlusal scheme, occasionally some dentists will attempt to reorganize the occlusion in the belief that this may redistribute the forces and reduce the amount of damage inflicted on the dentition. Sometimes termed "occlusal rehabilitation" or "occlusal equilibration", this can be a complex procedure, and there is much disagreement between proponents of these techniques on most of the aspects involved, including the indications and the goals. It may involve orthodontics, restorative dentistry or even orthognathic surgery. Some have criticized these occlusal reorganizations as having no evidence base, and irreversibly damaging the dentition on top of the damage already caused by bruxism.
History
Two thousand years ago, Shuowen Jiezi by Xu Shen documented the definition of Chinese character "齘" (bruxism) as "the clenching of teeth" (齒相切也).
In 610, Zhubing yuanhou lun by Chao Yuanfang documented the definition of bruxism (齘齒) as "the clenching of teeth during sleep" and explained that it was caused by Qi deficiency and blood stasis. In 978, Taiping Shenghuifang by Wang Huaiyin gave a similar explanation and three prescriptions for treatment. | Bruxism | Wikipedia | 299 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
"La bruxomanie" (a French term, translates to bruxomania) was suggested by Marie Pietkiewics in 1907. In 1931, Frohman first coined the term bruxism. Occasionally recent medical publications will use the word bruxomania with bruxism, to denote specifically bruxism that occurs while awake; however, this term can be considered historical and the modern equivalent would be awake bruxism or diurnal bruxism. It has been shown that the type of research into bruxism has changed over time. Overall between 1966 and 2007, most of the research published was focused on occlusal adjustments and oral splints. Behavioral approaches in research declined from over 60% of publications in the period 1966–86 to about 10% in the period 1997–2007. In the 1960s, a periodontist named Sigurd Peder Ramfjord championed the theory that occlusal factors were responsible for bruxism. Generations of dentists were educated by this ideology in the prominent textbook on occlusion of the time, however therapy centered around removal of occlusal interference remained unsatisfactory. The belief among dentists that occlusion and bruxism are strongly related is still widespread, however the majority of researchers now disfavor malocclusion as the main etiologic factor in favor of a more multifactorial, biopsychosocial model of bruxism.
Society and culture
Clenching the teeth is generally displayed by humans and other animals as a display of anger, hostility or frustration. It is thought that in humans, clenching the teeth may be an evolutionary instinct to display teeth as weapons, thereby threatening a rival or a predator. The phrase "to grit one's teeth" is the grinding or clenching of the teeth in anger, or to accept a difficult or unpleasant situation and deal with it in a determined way.
In the Bible there are several references to "gnashing of teeth" in both the Old Testament, and the New Testament, where the phrase "weeping and gnashing of teeth" appears no less than 7 times in Matthew alone.
A Chinese proverb has linked bruxism with psychosocial factors. "If a boy clenches, he hates his family for not being prosperous; if a girl clenches, she hates her mother for not being dead."(男孩咬牙，恨家不起；女孩咬牙，恨妈不死。) | Bruxism | Wikipedia | 512 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
In David Lynch's 1977 film Eraserhead, Henry Spencer's partner ("Mary X") is shown tossing and turning in her sleep, and snapping her jaws together violently and noisily, depicting sleep bruxism. In Stephen King's 1988 novel The Tommyknockers, the sister of central character Bobbi Anderson also had bruxism. In the 2000 film Requiem for a Dream, the character of Sara Goldfarb (Ellen Burstyn) begins taking an amphetamine-based diet pill and develops bruxism. In the 2005 film Beowulf & Grendel, a modern reworking of the Anglo-Saxon poem Beowulf, Selma the witch tells Beowulf that the troll's name Grendel means "grinder of teeth", stating that "he has bad dreams", a possible allusion to Grendel traumatically witnessing the death of his father as a child, at the hands of King Hrothgar. The Geats (the warriors who hunt the troll) alternatively translate the name as "grinder of men's bones" to demonize their prey. In George R. R. Martin's A Song of Ice and Fire series, King Stannis Baratheon grinds his teeth regularly, so loudly it can be heard "half a castle away".
In rave culture, recreational use of ecstasy is often reported to cause bruxism. Among people who have taken ecstasy, while dancing it is common to use pacifiers, lollipops or chewing gum in an attempt to reduce the damage to the teeth and to prevent jaw pain. Bruxism is thought to be one of the contributing factors in "meth mouth", a condition potentially associated with long term methamphetamine use. | Bruxism | Wikipedia | 363 | 155131 | https://en.wikipedia.org/wiki/Bruxism | Biology and health sciences | Mental disorders | Health |
Hair removal is the deliberate removal of body hair or head hair. This process is also known as epilation or depilation.
Hair is a common feature of the human body, exhibiting considerable variation in thickness and length across different populations. Hair becomes more visible during and after puberty. Additionally, men typically exhibit thicker and more conspicuous body hair than women.
Both males and females have visible body hair on the head, eyebrows, eyelashes, armpits, genital area, arms, and legs. Males and some females may also have thicker hair growth on their face, abdomen, back, buttocks, anus, areola, chest, nostrils, and ears. Hair does not generally grow on the lips, back of the ear, the underside of the hands or feet, or on certain areas of the genitalia.
Hair removal may be practiced for cultural, aesthetic, hygienic, sexual, medical, or religious reasons. Forms of hair removal have been practiced in almost all human cultures since at least the Neolithic era. The methods used to remove hair have varied in different times and regions.
The term "depilation" is derived from the Medieval Latin "depilatio," which in turn is derived from the Latin "depilare," a word formed from the prefix "de-" and the root "pilus," meaning "hair."
History
For centuries, hair removal has long shaped gender roles, served to signify social status and defined notions of femininity and the ideal "body image". In early periods, the condition of being hairless was mostly done as a way to keep the body clean, using flint, seashells, beeswax and various other depilatory utensils and exfoliator substances, some highly questionable and highly caustic. Ancient Rome also associated hair removal with status: a person with smooth skin was associated with purity and superiority. Removing body hair was done by both men and women
Psilothrum or psilotrum () and dropax () were depilatories in ancient Greece and Rome. | Hair removal | Wikipedia | 427 | 155140 | https://en.wikipedia.org/wiki/Hair%20removal | Biology and health sciences | Hygiene and grooming: General | Health |
In Ancient Egypt, besides being a fashion statement for affluent Egyptians of all genders, hair removal served as a treatment for louse infestation, which was a prevalent issue in the region. Very often, they would replace the removed head hair with a Nubian wig, which was seen as easier to maintain and also fashionable. Ancient Egyptian priests also shaved or depilated all over daily, so as to present a "pure" body before the images of the gods.
In ancient times, one highly abrasive depilatory paste consisted of an admixture of slaked lime, water, wood-ash and yellow orpiment (arsenic trisulfide); In rural India and Iran, where this mixture is called vajibt, it is still commonly used to remove pubic hair. In other cultures, oil extracted from unripe olives (which had not reached one-third of their natural stage of ripeness) was used to remove body hair.
During the medieval period, Catholic women were expected to let their hair grow long as a display of femininity, whilst keeping the hair concealed by wearing a wimple headdress in public places. The face was the only area where hair growth was considered unsightly; 14th-century ladies would also pick off hair from their foreheads to recede the hairline and give their face a more oval form. From the mid-16th century, it is said when Queen Elizabeth I came to power, she made eyebrow removal fashionable.
By the 18th century, body hair removal was still considered a non-necessity by European and American women. But in 1760, when the first safety straight razor appeared for men to safely shave their beard and not inadvertently cut themselves, some women allegedly used this safety razor too. It was invented in Paris by the French master cutler , author of La pogonotomie, ou L'art d'apprendre à se raser soi-même (Pogonotomy, or The Art of Learning to Shave). | Hair removal | Wikipedia | 413 | 155140 | https://en.wikipedia.org/wiki/Hair%20removal | Biology and health sciences | Hygiene and grooming: General | Health |
It was not until the late 19th century that women in Europe and America started to make hair removal a component of their personal care regime. According to Rebecca Herzig, the modern-day notion of body hair being unwomanly can be traced back to Charles Darwin's book first published in 1871 "The Descent of Man and Selection in Relation to Sex". Darwin's theory of natural selection associated body hair with "primitive ancestry and an atavistic return to earlier less developed forms", writes Herzig, a professor of gender and sexuality studies at Bates College in Maine. Darwin also suggests having less body hair was an indication of being more evolved and sexually attractive. As Darwin's ideas polarized, other 19th century medical and scientific experts started to link hairiness to "sexual inversion, disease pathology, lunacy, and criminal violence". Those connotations were mostly applied to women's and not men's body hair.
By the early 20th century, the upper- and middle-class white America increasingly saw smooth skin as a marker of femininity, and female body hair as repulsive, with hair removal giving "a way to separate oneself from cruder people, lower class and immigrant".
Harper's Bazaar, in 1915, was the first women's fashion magazine to run a campaign devoted to the removal of underarm hair as "a necessity". Shortly after, Gillette launched the first safety razor marketed specifically for women—the "Milady Décolleté Gillette", one that solves "...an embarrassing personal problem" and keeps the underarm "...white and smooth".
Cultural and sexual aspects
Body hair characteristics such as thickness and length vary across human populations, some people have less pronounced body hair and others have more conspicuous body hair characteristics.
Each culture of human society developed social norms relating to the presence or absence of body hair, which has changed from one time to another. Different standards of human physical appearance and physical attractiveness can apply to females and males. People whose hair falls outside a culture's aesthetic body image standards may experience real or perceived social acceptance problems, psychological distress and social pressure. For example, for women in several societies, exposure in public of body hair other than head hair, eyelashes and eyebrows is generally considered to be unaesthetic, unattractive and embarrassing. | Hair removal | Wikipedia | 477 | 155140 | https://en.wikipedia.org/wiki/Hair%20removal | Biology and health sciences | Hygiene and grooming: General | Health |
With the increased popularity in many countries of women wearing fashion clothing, sportswear and swimsuits during the 20th century and the consequential exposure of parts of the body on which hair is commonly found, there has emerged a popularization for women to remove visible body hair, such as on legs, underarms and elsewhere, or the consequences of hirsutism and hypertrichosis. In most of the Western world, for example, the vast majority of women regularly shave their legs and armpits, while roughly half also shave hair that may become exposed around their bikini pelvic area (often termed the "bikini line").
In Western and Asian cultures, in contrast to most Middle Eastern cultures, a majority of men are accustomed to shaving their facial hair, so only a minority of men reveal a beard, even though fast-growing facial hair must be shaved daily to achieve a clean-shaven or beardless appearance. Some men shave because they cannot genetically grow a "full" beard (generally defined as an even density from cheeks to neck), their beard color is genetically different from their scalp hair color, or because their facial hair grows in many directions, making a groomed or contoured appearance difficult to achieve. Some men shave because their beard growth is excessive, unpleasant, or coarse, causing skin irritation. Some men grow a beard or moustache from time to time to change their appearance or visual style.
Some men tonsure or head shave, either as a religious practice, a fashion statement, or because they find a shaved head preferable to the appearance of male pattern baldness, or in order to attain enhanced cooling of the skull – particularly for people suffering from hyperhidrosis. A much smaller number of Western women also shave their heads, often as a fashion or political statement.
Some women also shave their heads for cultural or social reasons. In India, tradition required widows in some sections of the society to shave their heads as part of being ostracized (see ). The outlawed custom is still infrequently encountered mostly in rural areas. Society at large and the government are working to end the practice of ostracizing widows. In addition, it continues to be common practice for men to shave their heads prior to embarking on a pilgrimage. | Hair removal | Wikipedia | 466 | 155140 | https://en.wikipedia.org/wiki/Hair%20removal | Biology and health sciences | Hygiene and grooming: General | Health |
The unibrow is considered a sign of beauty and attractiveness for women in Oman and for both genders in Tajikistan, often emphasized with kohl. In Middle Eastern societies, regular trimming or removal of female and male underarm hair and pubic hair has been considered proper personal hygiene, necessitated by local customs, for many centuries. Young girls and unmarried women, however, are expected to retain their body hair until shortly before marriage, when the whole body is depilated from the neck down.
In China, body hair has long been regarded as normal, and even today women are confronted with far less social pressure to remove body hair. The same attitude exists in other countries in Asia. While hair removal has become routine for many of the continent's younger women, trimming or removing pubic hair, for instance, is not as common or popular as in the Western world, where both women and men may trim or remove all their pubic hair for aesthetic or sexual reasons. This custom can be motivated by reasons of potentially increased personal cleanliness or hygiene, heightened sensitivity during sexual activity, or the desire to take on a more exposed appearance or visual appeal, or to boost self-esteem when affected by excessive hair. In Korea, pubic hair has long been considered a sign of fertility and sexual health, and it has been reported in the mid-2010s that some Korean women were undergoing pubic hair transplants, to add extra hair, especially when affected by the condition of pubic atrichosis (or hypotrichosis), which is thought to affect a small percentage of Korean women.
Unwanted or excessive hair is often removed in preparatory situations by both sexes, in order to avoid any perceived social stigma or prejudice. For example, unwanted or excessive hair may be removed in preparation for an intimate encounter, or before visiting a public beach or swimming pool.
Though traditionally in Western culture women remove body hair and men do not, some women choose not to remove hair from their bodies, either as a non-necessity or as an act of rejection against social stigma, while some men remove or trim their body hair, a practice that is referred to in modern society as being a part of "manscaping" (a portmanteau expression for male-specific grooming). | Hair removal | Wikipedia | 461 | 155140 | https://en.wikipedia.org/wiki/Hair%20removal | Biology and health sciences | Hygiene and grooming: General | Health |
Fashions
The term "glabrousness" also has been applied to human fashions, wherein some participate in culturally motivated hair removal by depilation (surface removal by shaving, dissolving), or epilation (removal of the entire hair, such as waxing or plucking).
Although the appearance of secondary hair on parts of the human body commonly occurs during puberty, and therefore, is often seen as a symbol of adulthood, removal of this and other hair may become fashionable in some cultures and subcultures. In many modern Western cultures, men are encouraged to shave their beards, and women are encouraged to remove hair growth in various areas. Commonly depilated areas for women are the underarms, legs, and pubic hair. Some individuals depilate the forearms. In recent years, bodily depilation in men has increased in popularity among some subcultures of Western males.
For men, the practice of depilating the pubic area is common, especially for aesthetic reasons. Most men will use a razor to shave this area, however, as best practice, it is recommended to use a body trimmer to shorten the length of the hair before shaving it off completely.
Cultural and other influences
In ancient Egypt, depilation was commonly practiced, with pumice and razors used to shave. In both Ancient Greece and Ancient Rome, the removal of body and pubic hair may have been practiced among both men and women. It is represented in some artistic depictions of male and female nudity, examples of which may be seen in red figure pottery and sculptures like the Kouros of Ancient Greece in which both men and women were depicted without body or pubic hair. Emperor Augustus was said, by Suetonius, to have applied "hot nutshells" on his legs as a form of depilation. | Hair removal | Wikipedia | 381 | 155140 | https://en.wikipedia.org/wiki/Hair%20removal | Biology and health sciences | Hygiene and grooming: General | Health |
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