Drinking water could be out of reach for nearly 400,000 Californians, analysis reveals

An estimated 370,000 Californians depend on drinking water which may contain high levels of arsenic, nitrate or hexavalent chromium, and contaminated drinking water has a disproportionate impact on communities of color in the state, according to a new analysis led by researchers at the University of California, Berkeley and the University of California at Los Angeles.

Since this study is limited to three common contaminants, the results likely underestimate the true number of Californians affected by unsafe drinking water from other chemicals. Populations at risk are found throughout the state, but are unsurprisingly concentrated in poor, mostly rural areas of the San Joaquin Valley, which rely heavily on private wells for domestic water. “

Dr Lara Cushing, Jonathan and Karin Fielding Presidential Chair of the Fielding School of Public Health at UCLA and Assistant Professor in Environmental Health Sciences

This study, available in the current edition of the peer-reviewed journal American Journal of Public Health, itself published by the American Public Health Association, is the first to quantify the average concentrations of several chemical contaminants in community water systems and domestic well areas statewide, and to analyze systematically demographic disparities in the quality of drinking water.

California’s human right to water law sets out the right to clean, affordable drinking water for people served by both community water systems and domestic wells, ”said Dr. Rachel Morello-Frosch, professor at the Berkeley School of Public Health at the University of California in the Department of Environmental Science, Policy and Management and senior author with Cushing’s research. “The implementation of this right is a significant challenge for people who depend on national wells due to the lack of regulatory infrastructure. “

Addressing inequalities in access to safe and clean drinking water will only become more urgent as climate change leads to prolonged droughts and limits water availability in the state, added Morello-Frosch.

“Our data strongly indicates that large numbers of people who depend on domestic wells are likely to drink water with high levels of contaminants, and suggest places where we should start targeted assessments to ensure that the human right to water is fully implemented, ”she said. .

Since 2012, access to safe, clean and affordable drinking water has been recognized as a human right in the state of California. Community water systems are required by federal regulations to undergo regular testing for contaminants that are harmful to human health. However, many California community water systems do not meet regulatory standards. In addition, many largely rural households receive their tap water from private domestic wells which remain largely unregulated.

The study focused on three chemical contaminants -; arsenic, nitrate and hexavalent chromium -; depending on their prevalence in the state, as well as their known toxicity. Arsenic is found naturally in groundwater and can be concentrated by depleting the water table. Contamination of groundwater with nitrates is common in agricultural areas due to runoff of fertilizers and factory farming of animals. Hexavalent chromium is produced by industrial and manufacturing activities.

According to the analysis, about 1.3 million Californians -; nearly three and a half percent -; depend on domestic wells for their water supply. Of the estimated 370,000 Californians whose water supplies have been found to likely contain high concentrations of arsenic, nitrate or hexavalent chromium, more than 150,000 are served by domestic wells. The quality of water from domestic wells continues to be a data gap and is critical to ensuring that all Californians know what’s in their water and whether it is safe to drink.

“I think a lot of people might be surprised to learn that, given the state of California’s wealth, we still don’t have universal access to clean drinking water,” Cushing said. For the three chemical contaminants we looked at, we found that places with a higher proportion of people of color experienced higher levels of drinking water contamination. This pattern has already been documented in community water systems, particularly in the San Joaquin Valley, but our work is one of the first to examine the issue statewide and among well communities. domestic not served by public water systems. “

The study was carried out by scientists at UC Berkeley and UCLA in conjunction with researchers from the California Environmental Protection Agency and the Community Water Center. The team released an online drinking water tool where policymakers and members of the public can research where their water is coming from, as well as map areas of the state where groundwater sources are likely. contaminated with dangerous levels of arsenic, nitrate and hexavalent chromium. and 1,2,3-trichrolopropane.

The goal of the Drinking Water Tool is to provide rapid access to data that can inform efforts to protect the state’s drinking water and groundwater supplies, especially in disadvantaged communities. where the threats are greatest, ”said study co-author, postdoctoral fellow Clare Pace. scientist at UC Berkeley. “We would like to continue to refine the Drinking Water Tool in collaboration with the Community Water Center and in response to feedback from other organizations and decision makers who can help verify the data.”

The tool also allows users to compare information on the quality of drinking and groundwater with data on the demographics of communities across the state, and models how drought conditions may impact the availability of water. water for small community water systems (serving less than 10,000 people) and domestic wells. Overall, the San Joaquin Valley had the highest number of people who drink water rich in arsenic and nitrate. For hexavalent chromium, the San Joaquin Valley and Imperial County / Mohave Desert regions had the highest populations.

“In this era of climate change, our groundwater is becoming an increasingly valuable resource, and we are facing historic levels of drought and well failure,” Cushing said. “Even if a well does not fail, the lowering of the water table can impact water quality by concentrating contaminants, further exacerbating these problems.”

MethodsTo conduct the study, the researchers combined data on the state’s community water systems, domestic well permits, residential tax plots, building footprints, and census data to locate households Californians likely to be served by unregulated domestic wells. They then used measurements of drinking water and groundwater contamination statewide to estimate contaminant levels for those served by community water systems and domestic wells.


Journal reference:

Rhythm, C., et al. (2021) Inequalities in drinking water quality between domestic well communities and community water supply systems, California, 2011-2019. American Journal of Public Health. doi.org/10.2105/AJPH.2021.306561.

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