Analysis of Cumulative Cancer Risk Associated with Disinfection Byproducts in United States Drinking Water.
Level 5 - mechanism / opinion, no new human data
Environmental risk assessment and computational modeling study using secondary occurrence datasets.
PubMed 32213849 · doi:10.3390/ijerph17062149
What was done
Researchers conducted a side-by-side cancer risk assessment comparing toxicological and epidemiological risk models for drinking water disinfection byproducts. The analysis evaluated exposure to regulated and unregulated haloacetic acids and trihalomethanes using contaminant occurrence datasets from the U.S. EPA Fourth Unregulated Contaminant Monitoring Rule (UCMR4) alongside standard exposure parameters.
What was found
Toxicological risk modeling indicated that haloacetic acids (especially brominated species) contributed more to carcinogenic risk than trihalomethanes. The toxicologically modeled cumulative lifetime cancer risk using standard default parameters was 7.0 × 10⁻⁵ (range: 3.5 × 10⁻⁵ to 1.3 × 10⁻⁴), rising to 2.9 × 10⁻⁴ (range: 1.7 × 10⁻⁴ to 6.2 × 10⁻⁴) when incorporating age-sensitivity factors for early-life exposure. In contrast, epidemiological models estimated a cumulative lifetime cancer risk of approximately 3.0 × 10⁻³ (range: 2.1 × 10⁻⁴ to 5.7 × 10⁻³), or approximately 3 cases per 1,000 individuals served by community water systems.
Why it matters
The findings suggest that toxicological risk calculations may underestimate human cancer burden compared to epidemiological risk estimates, highlighting unregulated brominated haloacetic acids as key drivers of disinfection byproduct risk.
Limits
The abstract does not state the exact number of water systems evaluated. Findings rely on aggregate population-level exposure models and default physiological assumptions rather than direct individual-level exposure or clinical outcome tracking, leaving potential for residual confounding and exposure misclassification.
Cited by
- context The Environmental Working Group showed that over 122 million Americans drink tap water with high levels of chemicals known to cause cancer.
- context The Environmental Working Group showed that over 122 million Americans drink tap water containing high levels of chemicals known to cause cancer.