Studies such as this are not new. They can be alarming in their presentation but the ecologic study design does not allow for definitive conclusions. Expect to see more studies like this published and played up in the media this year as arsenic is one of the more popular contaminants to report on in an election year. No one wants arsenic in their drinking water so it is a good media attention grabber even if it adds little to our understanding.
Bulka CM, Jones RM, Turyk ME, Stayner LT, Argos M. Arsenic in drinking water and prostate cancer in Illinois counties: An ecologic study. Environmental Research. 2016 Apr 29;148:450-456. doi: 10.1016/j.envres.2016.04.030.
BACKGROUND: Inorganic arsenic is a lung, bladder, and skin carcinogen. One of the major sources of exposure to arsenic is through naturally contaminated drinking water. While positive associations have been observed between arsenic in drinking water and prostate cancer, few studies have explored this association in the United States.
OBJECTIVES: To evaluate the association between inorganic arsenic concentrations in community water systems and prostate cancer incidence in Illinois using an ecologic study design.
METHODS: Illinois Environmental Protection Agency data on arsenic concentrations in drinking water from community water systems throughout the state were linked with county-level prostate cancer incidence data from 2007 to 2011 from the Illinois State Cancer Registry. Incidence rates were indirectly standardized by age to calculate standardized incidence ratios (SIRs) for each county. A Poisson regression model was used to model the association between county-level SIRs and mean arsenic tertile (0.33-0.72, 0.73-1.60, and 1.61-16.23ppb), adjusting for potential confounders.
RESULTS: For counties with mean arsenic levels in the second tertile, the SIR was 1.05 (95% CI: 0.96-1.16). For counties with mean arsenic levels in the third tertile, the SIR was 1.10 (95% CI: 1.03-1.19). There was a significant linear dose-response relationship observed between mean arsenic levels and prostate cancer incidence (p for trend=0.003).
CONCLUSIONS: In this ecologic study, counties with higher mean arsenic levels in community water systems had significantly higher prostate cancer incidence. Individual-level studies of prostate cancer incidence and low-level arsenic exposure are needed.