Nearly one-third of Americans exposed to unregulated contaminants in drinking water

By Dr. Sanchari Sinha Dutta, Ph.D.Reviewed by Benedette Cuffari, M.Sc.Jan 22 2025

Study reveals racial disparities in drinking water contamination, with Hispanic and Black communities facing higher exposure to harmful chemicals linked to cancer and other health risks

Study: Socioeconomic Disparities in Exposures to PFAS and Other Unregulated Industrial Drinking Water Contaminants in US Public Water Systems. Image Credit: r.classen / Shutterstock.com

In a recent study published in Environmental Health Perspectives, researchers assess socioeconomic disparities in exposure to unregulated contaminants present in public water systems throughout the United States.

Persistent inequalities in safe drinking water

The establishment of the Safe Drinking Water Act (SDWA) led to significant improvements in drinking water quality in the U.S. over the past 50 years. However, many low-income communities and communities of color continue to have limited access to safe drinking water.

Unregulated contaminants refer to chemical, physical, and biological contaminants without enforceable standards under the SDWA. Industries, agricultural and livestock production, landfills, and wastewater are some of the major sources of unregulated contaminants. In 2021, 6,586 public water systems, which serve 19.6 million U.S. residents, exceeded the maximum contaminant levels (MCLs), which increases the risk of chronic diseases and long-term health issues in exposed populations.

Existing evidence has highlighted socioeconomic disparities in exposure to contaminated drinking water in the U.S. One factor contributing to these inequalities is the disproportional settlement of industrial and hazardous waste facilities in areas with poor socioeconomic status and higher percentages of non-Hispanic Black and Hispanic people.

About the study

In the current study, data from the U.S. Environmental Protection Agency (EPA) collected between 2013 and 2015 under its Unregulated Contaminant Monitoring Rule program were analyzed. The levels of four industrial contaminants were measured, of which included per- and polyfluoroalkyl substances (PFAS), 1,4-dioxane, 1,1-dichloroethane (1,1-DCA), and chlorodifluoromethane (HCFC-22).

Study findings

The study analysis included 4,815 public water systems that served over 97 million U.S. residents. One or more target contaminants were identified in 27% of analyzed public water systems, with 1,4-dioxane as the most frequently detected contaminant, followed by HCFC-22, 1,1-DCA, and PFAS.

The levels of PFAS, 1,4-dioxane, and 1,1-DCA exceeded health reference levels in 7.9% of public water systems that served 32 million people. The frequency of contaminant detection was significantly higher in large or urban systems, as well as systems using groundwater or a combination of groundwater and surface water.

Socioeconomic and sociodemographic disparities

Public water systems with detectable levels of contaminants were more likely to be present in counties with higher proportions of Hispanic and Black residents, as well as urban areas. However, this association was not observed in counties with higher proportions of economically deprived residents.

Higher proportions of Hispanic and Black residents were reported in areas close to pollution discharge sites including wastewater treatment plants, airports and military training areas, as well as industrial sites. When pollution sources were controlled for, persistent positive associations were observed between the proportions of Hispanic residents and detections of target contaminants.

About 2% of public water systems serving tribal land or U.S. territories had detectable levels of PFAS and HCFC-22. The PFAS detection frequency was slightly higher in public water systems serving U.S. as territories compared to those serving U.S. states. However, the detection frequencies for other contaminants in U.S. territory-serving public water systems were similar to or lower than those in U.S. state-serving water systems.

Study significance

About 27% of public water systems serving 97 million U.S. residents had at least one of the four targeted contaminants, including PFAS, 1,4-dioxane, 1,1-DCA, and HCFC-22. Each of these contaminants is associated with adverse health effects; for example, exposure to PFAS increases the risk of cancer, thyroid disease, high cholesterol, and other health problems.

Similarly, 1,4-dioxane, a solvent found in consumer products, is classified as a potential carcinogen. Chlorodifluoromethane, an ozone-depleting gas used in fluoropolymer production, is associated with cardiovascular and neurological complications. In contrast, exposure to 1,1-DCA, a solvent used in paints, plastics, and pesticides, increases the risk of cancer. 

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.”

Hispanic and Black residents are more likely to be exposed to these hazardous contaminants through their drinking water and live near pollution sources. Thus, the percentage of Hispanic and Black residents in a community appears to be a consistent predictor of poorer water quality.

Importantly, the racial disparities observed in the current study cannot be entirely explained by socioeconomic status. Other factors,s including racism and the historical practice of redlining, which led to the disproportionate siting of industrial facilities in communities of color, likely contribute to the increased risk of exposure in these communities.

Overall, the study findings confirm the influence of demographic characteristics on drinking water quality and emphasize the crucial need for federal action to regulate these contaminants and provide communities of color with more resources to address the impacts of pollution.