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CANCER DOSE-RESPONSE STUDIES
Impact/Purpose:
Recently, EPA published new guidelines for carcinogen risk assessment that set forth principles and procedures to guide scientists in the conduct of Agency cancer risk assessments. The new guidelines emphasize the need to present a detailed weight-of-evidence discussion for establishing a mode of action for a chemical s carcinogenicity. Research on mechanisms of action is necessary to interpret the biological significance of an effect and to provide a sound scientific basis for assessing risk. The results of these studies will support the Agency's decision making process for a chemical's carcinogenic potential. The data will be used to inform the proposed MCLGs/MCLs for particular DBPs in the Stage 2 DBP rule and subsequent revisions.
Description:
Bromate- Ozone has been proposed for water disinfection because it is more efficient in killing microbes than chlorine and results in much lower levels of carcinogenic trihalomethanes than chlorination. Ozone leads to formation of hypobromous acid in surface waters with high bromine content and forms brominated organic byproducts and bromate. The carcinogenicity and chronic toxicity of potassium bromate (KBrO3) was studied in male B6C3F1 mice and F344/N rats to confirm and extend the results of previous work. Additional work on bromate-induced oxidative stress and its contribution to renal carcinogenicity as a key event the cancer mode of action are being carried out in support of the established MCL for bromate.