Jan 17, 2022

New Analysis Led by Californian Researchers Identifies Extent of Contaminants in Drinking Water

The study covers arsenic, nitrate and hexavalent chromium


A new analysis led by researchers at the University of California, Berkeley, and the University of California, Los Angeles identified the relationship between Californians and drinking water.

According to the study, an estimated 370,000 Californians rely on drinking water which may contain high levels of arsenic, nitrate or hexavalent chromium. The contamination also disproportionately impacts communities of color in the state, reported Berkley News.

This study is limited to three common contaminants, however, so a limitation is that its results likely underestimate the actual number of Californians drinking unsafe drinking water. 

The study consisted of: combining data on the state’s community water systems; domestic well permits; residential tax parcels; building footprints; and census results. Then, measurements of drinking water and groundwater contamination were used throughout the state to estimate contaminant levels for those served by both community water systems and domestic wells.

This study is published in the American Journal of Public Health, and is the first to quantify average concentrations of multiple contaminants in community water systems and domestic well areas statewide. The study is also the first to systematically analyze demographic disparities in drinking water quality across California.

“California’s Human Right to Water Law articulates the right to clean and affordable drinking water for people served by both community water systems and domestic wells, but implementing this right is a significant challenge for people who rely on domestic wells because of the lack of regulatory infrastructure,” said study co-senior author Rachel Morello-Frosch, a professor of public health and of environmental science, policy and management at UC Berkeley, reported Berkley News. “Our data strongly indicate that a large number of people who rely on domestic wells are likely drinking water with high levels of contaminants and suggest locations where we should begin targeted assessments to ensure that the human right to water is fully implemented.”


According to the analysis, approximately 1.3 million Californians rely on domestic wells for their water supply. Of the estimated 370,000 Californians whose water supply was found to likely contain high concentrations of arsenic, nitrate or hexavalent chromium, more than 150,000 are served by domestic wells. 

Access to safe, clean and affordable drinking water has been recognized as a human right in the state of California since 2012. Berkeley News reports that California community water systems do not meet regulatory standards and many rural households receive tap water from private domestic wells, which also are generally unregulated.

The study mentions that industrial and agricultural activity are potential sources of contaminants.

The team also created a Drinking Water Tool to show Californians how to find out where their drinking water comes from and map groundwater contamination with arsenic, nitrate, hexavalent chromium and 1,2,3-Trichloropropane. 

The study was carried out by UC Berkeley and UCLA scientists in collaboration with researchers at the California Environmental Protection Agency (CalEPA) and the Community Water Center

Co-authors of the study include Carolina Balazs and Komal Bangia from the CalEPA Office of Environmental Health Hazard Assessment, Nicholas Depsky from UC Berkeley and Adriana Renteria. The work was supported by the National Institute of Environmental Health Sciences (NIEHS), Award P42ES004705, and by a California Proposition 1 Sustainable Groundwater Planning Grant Award 4600012684.

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