Annual cancer risks from chemicals in North Carolina community water systems

ABSTRACT

Motivated partly by concerns about cancer, the U.S. Congress in 1986 amended the Safe Drinking Water Act (SDWA) by requiring that community water systems monitor 81 chemicals and remove those detected at concentrations above health-based standards. No prior research has used the resulting 30 years of monitoring data to analyze cancer risks from chemicals in US drinking water. To fill this gap, this paper uses chemical monitoring data from North Carolina's (NC's) 2,120 community water systems along with a risk assessment approach commonly applied in global burden of disease studies to quantify cancer risks of regulated chemicals in drinking water. The results indicate that 0.30% of NC cancer deaths are attributable to regulated drinking water contaminants and that the average annual individual risk is 7.2 × 10⁻⁶. More than 99% of this risk arises from disinfection by-products, with the remaining risk mostly attributable to arsenic and alpha particle radiation. In no water system does the combined risk from chemicals other than disinfection by-products, arsenic, or alpha particles exceed 10⁻⁴. The results suggest that regulated chemicals pose very low cancer risks and that risks from chemicals other than disinfection by-products, arsenic, and alpha particles are negligible in NC community water systems.

KEYWORDS:

• drinking water
• chemical contaminants
• cancer risk assessment
• burden of disease
• SDWA

Acknowledgments

We are grateful to Julia Cavalier and Eric Chai (NCDENR) and to Chandrika Rao and Sohrab Ali (NCDHHS) for providing the data used in this analysis.