Per/polyfluoroalkyl Substances (PFAS) in Residential Tap Water: Source-to-Tap Science for Underserved Communities

Science Center Objects

Per- and polyfluoroalkyl substances (PFAS) were detected at low levels in treated drinking water samples from residential taps in the Greater Chicago Area. This study is part of a larger approach to provide an understanding of contaminant mixtures in residential tap water across the Nation including underserved communities in rural, urban, and tribal areas. 

Due to the wide variety of uses and environmental persistence, per- and polyfluoroalkyl substances (PFAS) have been found in ambient and drinking water resources, air, soils, and in humans throughout the Nation. Previous science has shown that human exposure to PFAS typically occurs through ingestion of drinking water and food resources in addition to exposure through inhalation of air and dust.

As a component of ongoing research with a coalition of partners, including the U.S. Geological Survey, U.S. Environmental Protection Agency, National Institute of Environmental Health Sciences, Colorado School of Mines, University of Illinois Chicago, and University of South Carolina, water was collected from the taps of 45 Chicago-area residences and analyzed for 39 per/polyfluoroalkyl substances (PFAS) as part of a complete suite of 540 organic and 35 inorganic chemicals contaminants. This pilot study in the Chicago area complements a 2016 reconnaissance study of 12 business and 13 residential tapwaters in 11 states throughout the United States. 

As a reflection of the efficacy of water treatment by the Chicago area drinking water facilities, no Federal drinking water standards were exceeded in any sample collected and 90 percent of organic chemicals analyzed were not detected in treated tapwater samples. Consistent with previous findings from a reconnaissance study in homes and businesses throughout the United States, low-level concentrations of 11 PFASs were detected in greater than 95 percent of the treated tap water samples collected in this study. The U.S. Environmental Protection Agency 70 nanogram per liter advisory was not exceeded in any sample. 

Person collecting a water sample from a residential tap

U.S. Geological Survey scientist collecting a water sample from a home faucet for analyses of inorganic and organic chemicals. They use an integrated approach to understand drinking water from its sources, through watersheds, aquifers, and infrastructure to tap water where human exposure could occur. (Credit: U. S. Geological Survey. Public domain.)

While the results of this study emphasize the high quality and effective treatment of the drinking water in the area sampled, the results also demonstrate the potential for human exposure to low concentrations of chemical mixtures that are not commonly monitored or assessed at the point of exposure (tapwater). Although beyond the scope of this investigation, this study reveals a potential data gap in drinking water exposure assessments potentially needed for public health and for epidemiological and other researchers studying pathologic and toxicologic disease. The study results also provide information about sources and potential changes in contaminants as water moves from Lake Michigan to residential taps, including incoming contaminants that may be in the untreated source waters, chemical additions or removals through the treatment process, and changes through infrastructure and plumbing carrying treated water to tap. 

This research is designed to support decision makers focused on strategies to reduce human exposure and maintain the safety of U.S. drinking water supplies. Although water purveyors consistently monitor more than 100 chemical and microbial contaminants as part of compliance requirements under the Safe Drinking Water Act, there is a recognized lack of comprehensive data on other known, or suspected, contaminant mixtures such as PFAS in drinking water at the point of exposure in residences. This study continues to be a focus for the  U.S. Geological Survey’s Environmental Health Program in the Ecosystems Mission Area that studies contaminants and pathogens in water resources from their sources through watersheds, aquifers, and infrastructure to human and wildlife exposures. 

This research was funded by the U.S. Geological Survey’s Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology) in cooperation with the U.S. Environmental Protection Agency,  National Institute of Environmental Health Sciences, Colorado School of Mines, University of Illinois Chicago, and University of South Carolina.