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static/COU.md

@@ -6,7 +6,7 @@ The Color Hazard and RISk calculator (CHRIS) is (proposed to be) qualified to co
 Because CHRIS only addresses CAs, a favorable outcome by CHRIS does not imply acceptable biological risk for the final finished form of a medical device.  CHRIS is also not intended to establish device classification or identify biocompatibility requirements.  However, in addition to providing guidance to device manufacturers on acceptable levels of CA in a particular device, CHRIS can potentially be used to:
 
 * reduce the amount of biocompatibility testing needed following a supplier or manufacturing changes related to only the presence of the CA in the device;
-* obviate the need for additional biocompatibility testing when existing biocompatibility testing is inconclusive with respect to a CA. For example, the when biocompatibility extracts are colored, yet pass the testing (note that the presence of colored extracts may give rise to additional concerns unrelated to the color additive);
+* obviate the need for additional biocompatibility testing when existing biocompatibility testing is inconclusive with respect to a CA. For example, when biocompatibility extracts are colored, yet pass the testing (note that the presence of colored extracts may give rise to additional concerns unrelated to the color additive);
 * reduce the amount of biocompatibility testing needed for product lines with devices that are identical (*i.e.* materials and processing) with the exception of the presence and type of CA.
 
 In the absence of adequate toxicological and exposure data for a CA (or associated additives and impurities) in a polymeric matrix, a toxicological risk assessment can be conducted for systemic biocompatibility endpoints by comparing the total amount of a CA, associated additive, or impurities in the matrix to an appropriate threshold of toxicological concern (TTC).  This is the approach used by CHRIS in the absence of exposure and toxicity data for a particular system.  For the CAs listed below, CHRIS applies a CA-specific toxicological threshold value called a tolerable intake (TI) value.  These TIs are based on available systemic (including reproductive / developmental, genotoxicity, and carcinogenicity) toxicity data.  Because both the TTC and TI approaches are based on systemic toxicity, CHRIS can address acute systemic toxicity, subacute/subchronic toxicity, genotoxicity, carcinogenicity, and reproductive and developmental toxicity.  It does not, however, address cytotoxicity, sensitization, irritation, hemocompatibility, material mediated pyrogenicity, or implantation. Therefore, an MOS >= 1 implies the CA will not raise a safety concern with respect to only the systemic biocompatibility endpoints, which is reflected in the output of CHRIS.  Safety assessments have been performed, and TIs were derived for eleven (11) CAs commonly used in medical devices[^2]: