Harmful chemicals in the California water supply could lead to more than 15,000 cases of cancer, according to the findings of a new study.
Researchers from the Environmental Working Group, a consumer watchdog group, indicate that chemicals and contaminants in water are currently measured separately, instead of together. However, when combined, the cumulative effect suggests that many people throughout the state may be developing cancer due to the California drinking water.
The findings were published earlier this week, in the journal Environmental Health.
Researchers calculated the combined impact of carcinogens and other toxic contaminates in more than 2,700 community water systems in California, using data from the California State Water Resources Control Board. These water systems serve 98% of the state’s populations and regulated by the Federal Safe Drinking Water Act and overseen by state regulators.
The EWG study assessed the cumulative effect of all contaminants. It then provided a toxicity score reflecting potential health impacts of all contaminants present in drinking water.
Overall, 43% of the state’s water systems posed a high cancer risk. Furthermore, 500 of the community water systems evaluated were in the highest risk category. The data indicated drinking water from just these high risk systems alone, over a lifetime, would result in 4,860 cancer diagnoses.
While some large systems carried high cancer risks, according to the findings, water systems with the highest risk serve small communities of fewer than 1,000 people. Contaminants included arsenic, hexavalent chromium, disinfection byproducts, and radioactive elements like uranium and radium.
Of the contaminants found, 47% of estimated lifetime cancer cases were due to arsenic. Even at low level, arsenic is considered to be carcinogenic, and there are no safe levels, the researchers noted. Following arsenic, one-third of cancer cases were attributed to disinfection byproducts, or products used to treat drinking water.
The researchers indicated the risks have previously been missed, because health risks from drinking water contaminants are assessed one chemical at a time, which misses the health impacts of all the contaminants together.
“This cumulative approach is common in assessing the health impacts of exposure to air pollutants but has never before been applied to drinking water contaminants,” Dr. Tasha Stoiber, a senior scientist at EWG and the lead author of the study, said in an April 30 press release. “Right now, policymakers set health limits one chemical at a time. This doesn’t match reality. Multiple contaminants are often detected in drinking water across the U.S.”
This is the first study to assess the combined effect, instead of individual effects of each contaminant. The researchers said it underscores the need for improved water evaluation infrastructure and resources to provide safe drinking water to the general population.