A tarnished copper water pipe and spigot with dripping water sits in front of a blurred green outdoor background.
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Unsafe uranium levels have been detected in more than 14,000 community water systems across the United States, and 63% of water records reported at least a trace amount of the contaminant, according to a new nationwide analysis. Concentrations of uranium, along with arsenic, barium, chromium, and selenium, were the highest in community water systems that serve semiurban Latinx communities.

“Hispanic and Latino communities in the U.S. are impacted by high levels of metal concentrations in public water,” said Anne Nigra, an environmental health scientist at Columbia University in New York City and a lead investigator on the analysis. “We really should have federal financial and technological support and regulatory policies that are aimed at reducing exposure in these most highly exposed communities.”

Clean Water Inequities

The EPA monitors community water systems for a long list of potential contaminants that can cause harm to human health. Guided by the Safe Drinking Water Act and medical research, the agency sets maximum contamination levels for 10 metals in public drinking water systems: antimony, arsenic, barium, beryllium, cadmium, chromium, mercury, selenium, thallium, and uranium. The EPA publishes monitoring records from water systems every 6 years. But despite these efforts, regulated water systems across the country frequently report detections of lead, arsenic, and other contaminants in concentrations deemed unsafe by EPA standards. (Water contamination is also frequently reported in tribal water systems, which are not regulated by the EPA.)

“We are really interested in fully characterizing the magnitude of exposure for the entire U.S. population and also inequalities in exposures coming from regulated public drinking water systems,” Nigra said. “We want to understand comprehensively which types of communities and areas are disproportionately exposed to which contaminants.”

The researchers gathered more than 900,000 EPA records on average metal concentrations in nearly 38,000 community water systems nationwide during the early 2000s. Of the 10 metals monitored by the EPA, arsenic, barium, chromium, selenium, and uranium were detected in more than 10% of the records, so the research focused primarily on those contaminants. They found that 2.6% of all community water systems contained levels of arsenic exceeding EPA safe levels (10 micrograms per liter), and 2.1% of water systems contained unsafe levels of uranium (exceeding 30 micrograms per liter). Fewer than 0.1% of water systems contained unsafe levels of the other contaminants.

Four maps of the contiguous United States in a two-by-two grid show average concentrations of barium (top left), chromium (top right), selenium (bottom left), and uranium (bottom right) in community water systems in the early 2000s. Chromium concentrations were elevated in the central plains states. Chromium concentrations were elevated in central and western states, Nebraska, and Wisconsin. Selenium concentrations were elevated in only a few counties in western Texas, western Kansas, and eastern Nebraska. Uranium concentrations were elevated across the western half of the country, North Carolina, and New Jersey.
These maps of the contiguous United States show average concentrations of heavy metals in community water systems, measured in micrograms per liter (μg/L). The lightest shade of orange represents the minimum reporting quantity, and the darkest shade of orange represents the largest reported quantities. Credit: Ravalli et al., 2022, https://doi.org/10.1016/S2542-5196(22)00043-2, CC BY-NC-ND 4.0

In the case of uranium, 63% of all monitoring records reported trace amounts of the contaminant, which although below EPA levels, might still pose a health risk. When they saw how frequently water systems reported detectable levels of uranium, Nigra and her team decided to investigate which communities those water systems serve and who bears that health risk. They gathered data on whether a water system uses groundwater or surface water, the size of the community served, whether the system exclusively serves correctional facilities, the broad geographic region in which it is located, and the broad sociodemographic categories it serves.

They found that even among systems with similar water sources, geographic regions, and sizes, community water systems that serve semiurban Latinx communities contained not only the highest uranium concentrations but also the highest concentrations of arsenic, barium, chromium, and selenium.

“We didn’t expect that would be the case for all the metals that we looked at, and in fact, it was,” Nigra said. “That’s surprising because some of these metals co-occur together, like arsenic and uranium, but others do not tend to co-occur. So the finding that these metals were higher for these communities, across all of these metals which arise from very different geologic contexts, is very noteworthy.” These results were published in The Lancet Planetary Health on 6 April.

It’s Not the Geology

Natural geochemical reactions can cause uranium to appear in groundwater sources, especially in the southwestern and midwestern United States, Nigra explained, and human activities like mining can also release uranium into surface and groundwater. Although technology exists that can remove those contaminants from water systems, the technology sometimes can be too expensive for smaller municipalities to afford or maintain. However, because uranium and other metal concentrations were significantly higher for semiurban Latinx communities compared with other sociodemographic communities of similar size, geology, and water source, the researchers suggested that the unsafe uranium levels represent a consistent failure of regulatory policy to provide safe drinking water for Latinx communities.

“Communities of color as well as communities facing economic difficulties often have to deal with problematic tap water quality.”

This study “adds to the large body of research documenting that communities of color as well as communities facing economic difficulties often have to deal with problematic tap water quality,” said Olga Naidenko, who was not involved with this study. Naidenko is vice president of science investigations at Environmental Working Group (EWG), a nonprofit environmental advocacy group in Washington, D.C. She added that EWG “advocates for consideration of drinking water as a key metric in environmental justice, to ensure that communities that have experienced discrimination have access to sufficient funds for renovating and upgrading both drinking water and wastewater infrastructure.”

“Ultimately, I think we need a regulatory framework that protects the most highly exposed communities and the communities that are the most vulnerable or susceptible to the health impacts that are associated with these exposures,” Nigra said. “We’re trying to identify which types of communities have the highest exposures in order to hopefully influence federal and state financial and regulatory policies, in hopes that we can reduce these exposures and exposure disparities.”

There is little to no research exploring the potential health impacts of chronic exposure to low levels of uranium over long periods of time.

Exposure to uranium and the other metals analyzed in this study has been associated with negative health conditions, including cancers, liver damage, cardiovascular disease, and deterioration of kidney function. Most of these medical studies consider the impacts of exposure to high quantities of a contaminant, Nigra said, but there is little to no research exploring the potential health impacts of chronic exposure to low levels of uranium over long periods of time. It is an underrecognized and serious contaminant, she added.

The team has created publicly available interactive maps to allow people to learn about exposure risk where they live and hopefully to inspire more research into possible health impacts.

“We’re hoping to encourage epidemiologists to use this water concentration data to move the science forward,” she said, “to apply these concentration estimates to studies so that we can really understand the health impact of these low chronic exposures over decades of life.”

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer

Citation: Cartier, K. M. S. (2022), Uranium detected in Latinx communities’ water systems, Eos, 103, https://doi.org/10.1029/2022EO220199. Published on 21 April 2022.
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