Nearly One-Third of Americans Face Unregulated Contaminants in Water, Hispanic, Black Communities Hit Hardest

Nearly one-third of Americans have been exposed to unregulated contaminants in their drinking water that could impact their health.

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Nearly one-third of Americans have been exposed to unregulated contaminants in their drinking water that could impact their health, according to new research by scientists at the Silent Spring Institute.¹ The findings, published in Environmental Health Perspectives, also reveal significant racial disparities, with Hispanic and Black communities more likely to face unsafe levels of contaminants and live near pollution sources.

The US Safe Drinking Water Act requires monitoring and regulation of nearly 100 contaminants. However, thousands of potentially harmful chemicals are still unregulated. These substances enter groundwater and surface waters through industrial activities and consumer products, posing a hidden threat to public health.

“We know there are thousands of other harmful chemicals that are not regulated that make their way into groundwater and surface waters, and some of these chemicals can ultimately end up in drinking water supplies,” Laurel Schaider, senior scientist at Silent Spring Institute and co-author of the study, said in a statement.²

The researchers conducted an analysis of data collected by the US Environmental Protection Agency (EPA) between 2013 and 2015, as part of its Unregulated Contaminant Monitoring Rule program.¹ They reviewed records from 4815 public water systems and discovered that 27% of these systems, which serve a total of 97 million people, reported detectable levels of at least 1 concerning chemical. Among the identified contaminants were 1,4-dioxane, a solvent recognized as a probable human carcinogen that is also present in various consumer products; PFAS (per- and polyfluoroalkyl substances), often referred to as “forever chemicals,” which are linked to serious health issues such as cancer, thyroid disease, and high cholesterol; chlorodifluoromethane (Freon 22), an ozone-depleting gas commonly used in refrigerants and fluoropolymer production; and 1,1-dichloroethane, a solvent associated with cancer that is utilized in paints, plastics, and pesticides.

The study found significant disparities in the exposure to contaminants. Communities with higher percentages of Hispanic and Black residents were not only more likely to have unregulated chemicals in their drinking water, but they were also more frequently located near pollution sources, such as wastewater treatment plants, industrial sites, and military training areas. Further, the researchers emphasized that these disparities could not be attributed solely to income or other socioeconomic factors. Instead, systemic issues such as racism and historical redlining practices likely contribute to the disproportionate siting of industrial facilities in communities of color.

“Our findings show that the percentage of Hispanic and Black residents in a community is a consistent predictor of poorer water quality,” lead author Aaron Maruzzo, a scientist at Silent Spring Institute, stated.²

This study expands on earlier Silent Spring Institute research, which identified disproportionately high nitrate levels in water systems serving Hispanic communities. Although the EPA set nitrate limits decades ago to prevent "blue baby syndrome" in infants, emerging evidence suggests that even lower levels of nitrate exposure may elevate the risk of colorectal and bladder cancer. Furthermore, a 2023 study co-authored by Schaider revealed significantly higher concentrations of PFAS in water systems serving communities of color across 18 states, underscoring persistent disparities in water quality.

In April 2024, the EPA announced drinking water standards for 6 PFAS chemicals, but advocates argue more comprehensive measures are necessary. As the current analysis is the first to investigate disparities in exposure to PFAS and other unregulated contaminants across all US states, Tribal lands, and territories, these findings underscore the urgent need for stronger federal regulations and resources to address water quality issues. Recent testing indicates that PFAS contamination may be more widespread than previously thought, suggesting that the number of affected residents is likely underestimated.

“Ultimately, we need to do a better job at protecting source waters and reducing discharges of pollutants into water bodies that feed into our drinking water supplies,” Schaider stated.

For communities of color disproportionately affected by water contamination, expanded regulatory efforts and targeted resources could help mitigate health disparities and ensure safer drinking water for all, the study concluded.

References

1. Maruzzo AJ, Hernandez AB, Swartz CH, Liddie JM, Schaider LA. Socioeconomic disparities in exposures to PFAS and other unregulated industrial drinking water contaminants in U.S. public water systems. Environmental Health Perspectives. 2025. doi:10.1289/EHP14721

2. Over 97 million US residents exposed to unregulated contaminants in their drinking water. News release. Silent Spring Institute. January 15, 2025. Accessed January 15, 2024. https://www.eurekalert.org/news-releases/1069996