Millions in US Exposed to Unregulated Industrial Chemicals in Drinking Water

Almost 100 million people in the US may be exposed to unregulated industrial chemicals in their drinking water, with communities of color especially at risk, according to a new analysis of federal monitoring data for water systems across the country.

The study, published Wednesday in the journal Environmental Health Perspectives, analyzed data gathered by the US Environmental Protection Agency (EPA) from 2013 to 2015 for four types of unregulated chemicals, finding that 27% of those nearly 5,000 public water systems had detectable levels of at least one contaminant.

Overall, more than 97 million US residents were served by a public water system with detectable levels of the contaminants examined in the study.

The colorless, flammable solvent 1,4-dioxane was most pervasive, showing up in 22% of the public water systems, according to the study. The researchers also found the refrigerant HCFC-22, as well as a solvent called dichloroethane used in plastics production, and toxic per- and polyfluoroalkyl substances (PFAS) in about 4-6% of the water systems. The EPA data accounted for six types of PFAS, a category including thousands of chemicals: perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), perfluoroheptanoic acid (PFHpA) and perfluorobutane sulfonic acid (PFBS).

Hispanic and Black populations are at especially high risk for exposure to unregulated chemicals in their drinking water, the authors reported. Public water systems with detectable levels of the contaminants served counties with higher proportions of Hispanic residents than those with no detections, for example, the authors said.

“Our analysis found more frequent detections of unregulated industrial contaminants in public water systems serving higher proportions of Hispanic and non-Hispanic Black residents,” the study states. “Although some of the associations between race, ethnicity, and unregulated contaminants can be explained by disproportionate siting of industrial facilities, our analysis suggests that other factors contribute to disparities in exposures to unregulated drinking water contaminants.”

Study co-author Aaron Maruzzo, a researcher at the Silent Spring Institute, which studies links between environmental pollution and women’s health, said that previous research has focused on regulated contaminants, identifying racial and ethnic disparities in exposure to nitrates and arsenic.

In 2021, over 6,500 public water systems serving almost 20 million people across the US had violations for exceeding maximum levels for contaminants, according to EPA data. However, concerns around drinking water safety run deeper — while federal standards have been set for about 90 contaminants, more than 86,000 “potential chemical contaminants” are used in US commerce, according to the study.

The findings highlight “the need to consider both regulated and unregulated contaminants in future nationwide drinking water human health assessments,” said Kelly Smalling, a research hydrologist for the US Geological Survey who was not involved in the study.

Since the authors started their study, the EPA has gathered new data, but using the older data allowed the researchers to assess disparities in demographics of people exposed to the targeted chemicals at a time before any of them were regulated, said Laurel Schaider, a senior scientist at the Silent Spring Institute and another co-author of the study.

“It gave us a chance to kind of tease apart what are the factors that influence the occurrence of contaminants in drinking water maybe separate from the enforcement piece of it,” said Schaider.

The study found that unregulated contaminants were detected more frequently in large drinking water systems, systems in urban areas, and systems that relied on either groundwater or a combination of groundwater and surface water.

Recent data collected by EPA used lower detection limits and required water utilities to test for 29 types of PFAS compared to only six for the prior dataset, suggesting that the older data likely underestimated the number of people exposed to these so-called “forever chemicals,” the authors said.

While the Environmental Health Perspectives study found that about only 4% of the residents exposed to unregulated contaminants had PFAS in their drinking water, the more recent government data reported that more than 143 million people were exposed. The study authors said they plan to compare both sets of EPA data in a future analysis.

Last April, the EPA announced the first legally enforceable limits for six PFAS chemicals in drinking water.

“I’ll be interested to see how future research on drinking water disparities based on more comprehensive PFAS sampling data (i.e. samples with lower detection limits and samples collected from additional small water systems) adds to our understanding of the associations evaluated in this paper,” said Clare Pace, a scientist who studies water equity issues at the University of California, Berkeley and was not involved in the study.

In addition to PFAS, the study’s findings provide “an important reminder that there are still other unregulated industrial contaminants that are in drinking water that we need to be paying attention to,” said Schaider.

As drinking water systems put in place treatments to remove PFAS, they may have the added benefit of filtering out other harmful chemicals, such as pharmaceuticals, flame retardants and personal care products, she said.