According to an analysis by researchers at the University of California at Berkeley and UCLA, the drinking water of approximately 370,000 Californians is heavily contaminated with chemicals that harm human health.
The study, published December 22, 2021, focuses on three widespread chemical pollutants: arsenic, nitrate and hexavalent chromium. Arsenic is found naturally in groundwater, while nitrate and hexavalent chromium are often formed from agricultural and industrial activities.
Lara Cushing, assistant professor of environmental sciences and chair of the UCLA Fielding School of Public Health, said the number of residents affected by unsafe drinking water is likely an underestimate.
“Because this study is limited to three common contaminants, the results likely understate the actual number of Californians affected by unsafe drinking water due to other chemicals,” Cushing said in a statement.
She also said the most concentrated area affected by contaminated water is a poor and rural area in the San Joaquin Valley, about 40 miles east of San Francisco, where people rely heavily on private wells.
Although public water systems are usually monitored for contamination levels under federal law, many do not meet regulatory standards. Despite federal regulation, many private wells remain unregulated.
The analysis also shows that more than 1 million people in California rely on home wells for their water supply.
More than one-third of people whose water supply is likely to contain chemical contaminants now rely on home wells, according to the study.
“I think a lot of people might be surprised to know that given how rich the state of California is, we still don’t have universal access to clean drinking water,” Cushing said.
The team also released an online drinking water tool for Californians to find out where their water is coming from and a map of water pollution.
Drinking water with unsafe levels of contamination can cause gastrointestinal illness, reproductive effects, and chronic diseases such as cancer. According to the US Environmental Protection Agency, long-term exposure to chemicals can lead to severe organ damage, skin discoloration, and developmental effects.
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