Estimating National Exposures and Potential Bladder Cancer Cases Associated with Chlorination DBPs in U.S. Drinking Water

Abstract

Background: Disinfection byproducts (DBPs) in public water systems (PWS) are an unintended consequence resulting from reactions between mostly chlorine-based disinfectants and organic and inorganic compounds in source waters. Epidemiology studies have shown that exposure to DBP (specifically trihalomethanes) was associated with an increased risk of bladder cancer. Objective: Our goal was to characterize the relative differences in exposures and estimated potential bladder cancer risks for people served by different strata of PWS in the United States and to evaluate uncertainties associated with these estimates. Methods: We stratified PWS by source water type (surface vs. groundwater) and population served (large, medium, and small) and calculated population-weighted mean trihalomethane-4 (THM4) concentrations for each stratum. For each stratum, we calculated a population attributable risk (PAR) for bladder cancer using odds ratios derived from published pooled epidemiology estimates as a function of the mean THM4 concentration and the fraction of the total U.S. population served by each stratum of systems. We then applied the stratum-specific PARs to the total annual number of new bladder cancer cases in the U.S. population to estimate bladder cancer incidence in each stratum. Results: Our results show that approximately 8,000 of the 79,000 annual bladder cancer cases in the United States were potentially attributable to DBPs in drinking water systems. The estimated attributable cases vary based on source water type and system size. Approximately 74% of the estimated attributable cases were from surface water systems serving populations of people. We also identified several uncertainties that may affect the results from this study, primarily related to the use of THM4 as a surrogate measure for DBPs relevant to bladder cancer. Discussion: Despite significant reductions in exposure over the past several decades, our study suggests that of the bladder cancer cases in the United States may still be attributed to exposure to DBPs found in drinking water systems. https://doi.org/10.1289/EHP9985

Pomegranate (Punica granatum L.) Peel Extracts as Antimicrobial and Antioxidant Additives Used in Alfalfa Sprouts

“…The conventional method to maintain microbial safety in vegetables is through washing and disinfection with chlorine; however, it has been hypothesized that some chlorination byproducts may have carcinogenic potential. This has encouraged the quest for safe and effective alternatives [ 49 ].…”

Invited Perspective: Existing Rules for Disinfection By-Products Are Good, but They Are Not Enough

“…conducted the largest risk assessment of DBPs in the United States to date, focusing on bladder cancer cases associated with chlorinated drinking water. 3 The authors, most of them from the U.S. Environmental Protection Agency (EPA) Office of Water, obtained DBP data from public water systems serving 198 million people from 42 states. These data were collected as part of the third Six-Year Review of the DBP regulations.…”

“…Despite the difficulty in proving causality for suspected carcinogens, the weight of evidence supporting the link between DBPs and bladder cancer has increased since the Stage 2 DBP Rule. 3 Something interesting (and a bit unexpected) was the finding by Weisman et al. of greater risk of bladder cancer from large drinking water systems compared with small systems.…”

“…of greater risk of bladder cancer from large drinking water systems compared with small systems. 3 It is well known that DBP exceedances occur more often in small systems, 4 which typically do not have the resources of larger systems to install innovative treatment methods to reduce DBP levels.…”

“…also considered sources of uncertainty and whether the four regulated THMs (also known as THM4) are good surrogates for unregulated DBPs that have higher toxicity. 3 Emerging evidence suggests that haloacetonitriles and iodoacetic acids should be considered for future drinking water regulations. For example, a recent forcing factors study, which measured 72 DBPs and whole water cytotoxicity in a variety of impacted drinking waters across the United States, found that haloacetonitriles are important drivers of cytotoxicity.…”