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Individual and Additive Disinfectant Byproducts in Community Drinking Water Systems and Associations with Colorectal and Bladder Cancer Incidence, Accounting for Population Served
Citation:
Krajewski, A., M. Jimenez, D. Lobdell, Tim Wade, AND J. Jagai. Individual and Additive Disinfectant Byproducts in Community Drinking Water Systems and Associations with Colorectal and Bladder Cancer Incidence, Accounting for Population Served. 2018 ISEE/ISES Conference, Ottawa, Ontario, CANADA, August 26 - 30, 2018.
Impact/Purpose:
The purpose of this study was to examine drinking water disinfectant byproducts in relation to bladder and colorectal cancer in a community water system controlling for population served.
Description:
Disinfectant byproducts (DBPs) haloacetic acids (HAA5) and trihalomethanes (TTHM) used in community water systems (CWS) are potential bladder and colorectal carcinogens. Studies neglect to account for how exposures may differ within counties based on population served (PS) by CWS, which provides estimates of individual exposure. CWS concentration data for HAA5 and TTHM with PS were obtained for eight US states. These were summed to create additive DBP exposure and aggregated to the county-level to construct three cumulative county-level HAA5, TTHM, and additive DBP exposure metrics: unadjusted for PS; controlled for PS (as a covariate); and accounted for PS (concentration multiplied by proportion of PS by county population). Poisson regressions estimated incidence rate ratios (IRR) and 95% confidence intervals for associations between colorectal and bladder cancer and DBP, HAA5, and TTHM exposure tertiles, adjusting for potential confounders. For unadjusted DBP tertiles (732ppb), the IRRs were 1.27 (1.22,1.32) and 1.58 (1.53,1.64) for tertiles 2-3, compared to 502 ppb), the IRRs were 0.92 (0.88,0.96) and 1.46 (1.41,1.51) for tertiles 2-3, compared to <178 ppb. Associations between colorectal cancer and HAA5 and TTHM tertiles were similar to the DBP tertiles. Associations between bladder cancer and HAA5, TTHM, and DBP tertiles were also similar to colorectal. Differing measures of PS by CWS in measured drinking water HAA5, TTHM, and DBP concentrations resulted in positive but varied associations to colorectal and bladder cancer. Thus, PS may need to be considered when developing drinking water exposure measures. This abstract does not reflect EPA policy.