By studying water contaminants in groups, researchers assessed cancer risks over lifetimes
A study of contaminant groups in 2,737 public water systems in California found that the Golden State’s drinking water may cause negative health outcomes. The Environmental Working Group (EWG) study, published in the journal Environmental Health, found that concentrations of contaminants in California public water systems may contribute to approximately 15,500 cancer cases in the state over a lifetime. The water systems examined serve 98% of California’s population.
The study’s new methodology, which considers contaminant groups rather than studying the contaminants in isolation, may be as important as the study’s conclusion. The researchers said that studying the contaminants in isolation can miss health impacts of contaminants that co-occur in public water systems. They said:
Drinking water rarely contains only one contaminant, yet regulators currently assess the health hazards of tap water pollutants one by one. This ignores the combined effects of multiple pollutants, which is how people ingest them […]
A framework of cumulative risk is now frequently applied in evaluations of air quality, such as the National Air Toxics Assessment conducted by the United States Environmental Protection Agency (EPA). The researchers said drinking water assessments would likewise benefit from a more comprehensive framework, and called for further research to refine the methodology.
Contaminant Groups and Public Health
The research team of Tasha Stoiber, Alexis Temkin, David Andrews, Chris Campbell, and Olga V. Naidenko classified the water systems under study into four risk categories. The top risk classification carries an additional projected risk of more than 1 in 1,000 Californians being diagnosed with cancer in their lifetimes if they drink the tap water. Five hundred community water systems in California fall within this highest risk classification, and 4,860 cancer diagnoses are expected among those who drink from them over their lifetimes.
The study breaks down the California contaminant groups along with their estimated number of lifetime cancer deaths:
- Arsenic: 7,251
- Hexavalent chromium (the “Erin Brockovich” contaminant): 2,448
- Grouping of 9 byproducts of disinfection: 5,244
- Radioactive elements (radium and uranium): 345
- Grouping of five volatile organic compound (VOCs) carcinogens: 161
Small Communities Hit Hardest
The highest risks were observed in small and medium-size communities, which need new water treatment systems and water infrastructure to ensure safe drinking water. Finding affordable, up-to-date water treatment technologies is often difficult for these communities, but since 2012, California has promoted a Human Right to Water as a groundwork to aid communities without access to safe, affordable drinking water supplies. This right, coupled with the startling findings of the EWG study, will likely spur action by the state.
The EWG cumulative risk framework is important because it will help triage effective action. Moreover, the methodology can now help community water systems determine which specific water treatment technologies are needed to treat the specific combinations of contaminants found in their local water supplies.
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