New Maps Show Most Congressional Districts Have a PFAS Problem

Per- and polyfluoroalkyl substances (PFAS) are a large class of thousands of synthetic chemicals widely used for their oil and water repellency, temperature resistance, and friction reduction. They are used to produce items such as cookware, packaging, electronics, and cleaning products. PFAS can be harmful, even at extremely low doses. The EPA has found that there is no safe level of exposure to some of the most widely detected PFAS. They have been linked to serious health effects such as cancer, hormone disruption, kidney and liver damage, developmental and reproductive harm, and immune system toxicity. And due to their widespread use and our constant exposure, PFAS are now found in the bodies of virtually all Americans. They have earned the moniker “forever chemicals” because they do not break down easily and can accumulate in the environment. Some can last in the environment for thousands of years.

In April 2024, the EPA restricted six PFAS chemicals (PFOA, PFOS, PFHxS, GenX/HFPO-DA, PFNA, and PFBS) in drinking water, which it estimated could benefit up to 105 million people. The chemical industry sued to block the rule; water utility trade associations, which are responsible for protecting their customers’ health from toxic chemicals in tap water, joined the chemical industry to challenge the PFAS rule. NRDC and its allies are intervenors in that litigation, seeking to protect the standards.

In the wake of pressure from industry and congressional Republicans who urged the EPA to weaken these rules, on May 14, 2025, EPA Administrator Lee Zeldin announced plans to repeal health standards for the four PFAS that make up the “hazard index”: 

• GenX, the forever chemical that replaced PFOA, is widely used and has, for example, contaminated the drinking water source of 500,000 people in North Carolina
• PFHxS and PFNA, which are found in the blood of more than 95 percent of people living in the United States
• PFBS, a replacement for PFOS that is still actively being produced and used in the United States

The agency also plans to extend the compliance deadline for the other two legacy PFAS covered by the rules (PFOA and PFOS) by two years, from 2029 to 2031. If formally enacted, the EPA’s new actions would be unlawful under the Safe Drinking Water Act’s “anti-backsliding” provision, which says the agency cannot legally weaken drinking water standards. The law also provides that water systems get a maximum of five years to comply with drinking water standards, which the EPA’s April 2024 rule already provided. Any additional time for compliance can only be authorized on a case-by-case basis, and generally only by states, under strict conditions, after an opportunity for a public hearing on the extension.

To date, at least 73 million people are served by community water systems with at least one UCMR5 result above the EPA’s PFAS thresholds; 13 million of those people’s systems have at least one UCMR5 result above the thresholds that the EPA plans to roll back. It is important to note that UCMR5 monitoring covers an additional 23 PFAS that are not regulated by the EPA. When all of this data is included, almost half of the people whose water has been tested under this program are served by systems with some amount of PFAS contamination. As additional monitoring is completed, the populations affected by PFAS contamination of tap water will surely increase.

Representatives from Florida, Pennsylvania, and Texas serve congressional districts with the largest populations supplied by systems having PFAS that were detected above federal thresholds (Table 2). These representatives should be particularly interested in the UCMR5 results and upholding the MCLs to protect the health of their residents. 

The largest community water systems with one or more PFAS detected above a federal threshold are located in Florida, Pennsylvania, and Texas. However, there are also very large water systems with PFAS that were detected above federal thresholds located in California, Kentucky, New Jersey, New York, North Carolina, Ohio, Virginia, and Puerto Rico (Table 3).

The true number of people impacted by PFAS in their water is likely to be much larger, as current monitoring excludes most PFAS and the vast majority of small community water systems (serving under 3,300 people) are not tested under UCMR5. Thus, there are tens of thousands of these smaller water systems and private wells that are not represented in UCMR5 and the maps presented here. Furthermore, these numbers will increase as more results from the UCMR5 monitoring program are reported and as PFAS contamination continues to spread from pollution sources.

This is further supported by previous testing conducted by some states, which the EPA reviewed when setting the PFAS national drinking water standards. That testing revealed, for example, that GenX has been found at numerous locations across the country, beyond what the current UCMR5 testing reveals. It is likely that GenX—along with most PFAS—is present in far more water systems than is found by the limited UCMR5 testing.

These maps demonstrate that tens of millions of people across the country are currently at risk of drinking PFAS-contaminated water, and that risk may only increase for many years to come if the EPA successfully rolls back and delays PFAS standards. These actions are not only a violation of the Safe Drinking Water Act, but they would present a significant threat to public health in America. 

¹ Surprisingly for many people, the EPA’s drinking water standards for PFAS allow many sleights of hand that let water systems be in technical compliance with a Maximum Contaminant Level (MCL), even though they have detected PFAS at a level exceeding the stated threshold number in the MCL. For example, the rules require water systems to test their water multiple times and allow a system to average those sample results, subject to certain restrictions. Therefore, even if one or more samples exceed the MCL threshold, the running annual average might not exceed that level, and the system would technically not be in violation of the standard. The agency also allows water systems to report detections of PFAS at levels below the “practical quantitation limit” as zero—even though the lab found PFAS in the sample—and to use that zero in calculating the average level in the water. In addition, the EPA’s rule uses a “significant figure” sleight of hand to allow water systems to round their results downward when their test results would otherwise exceed the standard. So, for example, if a system’s average level of PFNA is 14 parts per trillion (ppt), the system can round down and say it’s in compliance with the MCL, since the standard is 10 ppt, with only the first digit being significant. See “PFAS National Primary Drinking Water Regulation.” The UCMR5 monitoring results reported here show at least one sample tested above an EPA threshold that was stated in the PFAS drinking water standards or multiple samples that tested above the threshold. We do not use the EPA’s averaging or significant figure approach in this map, so technically, systems may not be in violation of the MCLs even though their test results exceed the EPA’s MCL numerical thresholds. Only ongoing monitoring over time will determine whether a water system technically exceeds the EPA drinking water standard, consistent with the EPA’s rules. The EPA’s PFAS MCLs will not become enforceable until April 2029. As discussed in the text, however, in May 2025, the EPA announced that it intends to delay the compliance dates for two of these standards (PFOA and PFOS) by two years and to rescind the four other PFAS drinking water standards.