Nearly a third of people in the U.S. have been exposed to unregulated contaminants in their drinking water that could impact their health, according to a new analysis by scientists at Silent Spring Institute. What’s more, Hispanic and Black residents are more likely than other groups to have unsafe levels of contaminants in their drinking water and are more likely to live near pollution sources.
The findings, published in the journal Environmental Health Perspectives, add to growing concern about the quality of drinking water in the United States and the disproportionate impact of contamination on communities of color.
Close to 100 contaminants are currently regulated under the U.S. Safe Drinking Water Act. This means public water utilities must test for these contaminants and take steps to ensure levels don’t exceed certain limits by installing new treatment systems and taking other measures.
“Yet, 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,” says co-author Laurel Schaider, a senior scientist at Silent Spring Institute.
Schaider and her team looked at data from the U.S. Environmental Protection Agency (EPA) collected between 2013 and 2015 under its Unregulated Contaminant Monitoring Rule program. The team analyzed data from 4,815 public water systems and found 27 percent—serving 97 million residents—had detectable levels of at least one of the following chemicals:
- 1,4-dioxane, a solvent classified by EPA as a probable human carcinogen, also found in consumer products
- PFAS (per- and polyfluoroalkyl substances), non-stick chemicals widely used in consumer products, associated with cancer, thyroid disease, high cholesterol and other health problems
- chlorodifluoromethane (Freon 22), an ozone-depleting gas previously used as a refrigerant and used in the production of fluoropolymers (e.g. Teflon)
- 1,1-dichloroethane, a solvent used in paints, plastics, and pesticides associated with cancer.
Communities with a higher proportion of Hispanic and Black residents generally were more likely to be exposed to these unregulated contaminants in their drinking water and were more likely to be situated close to pollution discharge sites including wastewater treatment plants, airports and military training areas, and industrial sites.
“Our findings show that the percentage of Hispanic and Black residents in a community is a consistent predictor of poorer water quality,” says lead author Aaron Maruzzo, a scientist at Silent Spring Institute.
These racial disparities could not be explained by income or other measures of socioeconomic status, he says, suggesting that factors such as racism and the historical practice of redlining that led to the disproportionate siting of industrial facilities in communities of color could be playing a role.
The study builds on previous research by Silent Spring, which found Hispanic residents are more likely to be exposed to higher levels of nitrate in their drinking water. EPA set a legal limit on nitrate decades ago to protect infants from a fatal condition known as “blue baby syndrome.”. Newer evidence suggests exposure to nitrate at levels below the federal standard also can increase the risk of colorectal and bladder cancer.
A 2023 study, co-authored by Schaider, looked at community water systems in 18 states and found those with a higher proportion of Hispanic and Black residents had higher levels of PFAS in their drinking water. The new Silent Spring analysis is the first to look at disparities in exposure to PFAS and other unregulated contaminants in all U.S. states, as well as Tribal lands and U.S. territories.
In addition, recent testing shows PFAS are significantly more widespread in drinking water than previously thought, so the number of residents impacted by contaminants at the time the data were collected is an underestimate, says Schaider.
In April 2024, EPA announced drinking water standards for six PFAS chemicals. The study’s findings underscore the need for federal action to regulate more contaminants and provide communities of color with more resources to address the impacts of pollution.
“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,” says Schaider.
