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Analysis of Cumulative Cancer Risk Associated with Disinfection Byproducts in United States Drinking Water (308514)

Keywords: drinking water, disinfection byproducts, cancer risk, bladder cancer, cumulative risk assessment

Hundreds of different disinfection byproducts form in drinking water following necessary treatment with chlorine and other disinfectants, and many of those byproducts can damage DNA and increase the risk of cancer. This study offers the first side-by-side comparison of two cancer risk assessment methodologies, alternatively based on toxicological (animal) and epidemiological (human) data. These assessments use a comprehensive contaminant occurrence dataset for haloacetic acids and trihalomethanes, two groups of disinfection byproducts that are regulated in drinking water. We also provide the first analysis of a new occurrence dataset for unregulated haloacetic acids that became available from the latest, fourth round of the U.S. EPA-mandated unregulated contaminant monitoring program (UCMR4). Lifetime cancer risk is estimated at 7.0x10-5 (3.5x10-5 - 1.3x10-4) to 2.9x10-4 (1.7x10-4 - 6.2x10-4) using animal data and 3.0x10-3 (2.1x10-4 - 5.7x10-3) using epidemiological data. This study offers a compelling argument for conducting a cumulative risk assessment for both regulated and unregulated contaminants, and the analysis highlights the value of incorporating human health data.