Incarcerated Californians — and those who live in neighboring rural communities — may be exposed to dangerous levels of arsenic in their drinking water, a new study has found.

Arsenic concentrations in the water supply of the Kern Valley State Prison and three nearby Central Valley communities exceeded regulatory limits for months or even years at a time, according to the study, published on Wednesday in Environmental Health Perspectives. 

To draw their conclusions, the authors combed through 20 years of water quality data from the prison and the adjacent communities of Allensworth, McFarland and Delano, where groundwater aquifers contain unhealthy levels of naturally occurring arsenic.

Long-term exposure to even small amounts of arsenic in drinking water has been associated with a variety of cancers and other serious health issues, the authors warned.

“There has been a lot of work, primarily by journalists and by incarcerated people themselves, that suggests serious environmental health hazards in prisons,” first author Jenny Rempel, a graduate student in the University of California – Berkeley’s Energy and Resources Group, said in a statement.

“And yet there have been very few studies looking at these environmental health challenges,” Rempel continued. “This is one of the few studies to document ongoing structural challenges to realizing this basic human right to water on both sides of the prison walls.”

California recognized the human right to water in September 2012, when then-Gov. Jerry Brown (D) signed the bill AB-685 into law, the study authors noted. With that step, California became the first state in the country to recognize the human right to water via legislation. 

Yet across the state, about 370,000 Californians rely on drinking water that may contain high levels of the chemicals arsenic, nitrate or hexavalent chromium, another team of Berkeley researchers determined earlier this year. And such contamination, they found, disproportionately impacts communities of color and residents of rural regions.

The Environmental Protection Agency reduced the maximum contaminant level for arsenic from 50 parts per billion to 10 parts per billion in 2006, the authors of Wednesday’s study noted.

Yet the Kern Valley State Prison opened in 2005 without any plans for arsenic remediation, even though water quality data suggested that the system would fail to comply with these new standards, Rempel explained.

In fact, drinking water arsenic levels exceeded 10 parts per billion at the Kern Valley State Prison and in all three surrounding communities at various time in the past two decades, Rempel and her colleagues observed.

Sometimes, these levels persisted even after the region received state funding for arsenic remediation, according to the study.

The prison, for example, showed average arsenic levels of around 20 parts per billion until the completion of a $6 million treatment facility in 2013. But even with that system in place, arsenic levels occasionally spiked above 20 parts per billion between 2017 and 2019, the authors found.

“Although all four communities were meeting the federal arsenic standard at the end of our study period, we found persistent water injustices that reached across carceral boundaries,” Rempel said.

In the communities surrounding the prison, residents can choose to drink bottled water or install water filtration systems, the authors acknowledged. Nonetheless, they countered, many low-income households cannot afford to do so.

The researchers observed that the drinking water of Delano — the largest of the communities, with 50,000 residents — has almost never surpassed 10 parts per billion for arsenic since 2013, after new wells and arsenic treatment facilities were constructed.

But in McFarland — with just 12,000 residents — arsenic levels have occasionally exceeded 10 parts per billion, despite the addition of a new treatment system, according to the study. 

The even smaller community of Allensworth, which has only about 600 residents, does not yet have a treatment facility, the authors stressed. Instead, the town relies on water blended from two wells to bring down arsenic levels, as well as state-subsidized bottled water, they explained.

In light of these findings, Rempel and her colleagues called for increased support for water treatment facilities in low-income communities, as well as the implementation of new, affordable technologies that provide access to safe drinking water.

“But to really deliver on the promise of the human right to water, we need to establish adequate technical assistance and other creative approaches to ensure that communities are able to successfully operate treatment systems in the long term,” Rempel said.