People can be exposed to PFAS through drinking water, household dust, and food.

Our understanding of the impacts of PFAS in drinking water is limited to a handful of specific chemicals at present but is improving as research is conducted on these chemicals. The most studied PFAS are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). EPA currently identifies PFOA as “likely to be a carcinogen”, which is a step below a “carcinogenic” classification, because there is limited human data. PFOS is currently identified to have “suggestive evidence of carcinogenic potential”, which is less certain than the classification of PFOA.

In June 2022, EPA published interim lifetime health advisories for PFOA and PFOS which are at levels below what can reliably be measured in drinking water. Final lifetime health advisories were published for two replacement compounds, hexafluoropropylene dimer acid (HFPO-DA or “GenX”) and perfluorobutanesulfonic acid (PFBS). Collectively these health advisories noted that the health effects of PFAS may include cancer, liver effects, immunological effects, decreased birth weights, thyroid disease, decreased fertility, and cardiovascular disease.

Drinking water lifetime health advisories are developed by EPA and intended to provide information on contaminants that can cause human health effects and are known or anticipated to occur in drinking water. EPA has published lifetime health advisories for four PFAS: PFOA at 0.004 parts per trillion (ppt), PFOS at 0.020 ppt, GenX at 10 ppt, and PFBS 2,000 ppt. EPA sets advisory levels at concentrations at which there is certainty – with a margin of safety -- that there are no adverse health effects from drinking water exposure over a lifetime of exposure, including sensitive subpopulations like pregnant people, immunocompromised individuals, and children.

EPA develops health advisories by reviewing animal and human health studies to determine the levels of exposure at which individual adverse health effects may occur. EPA will consider strength of the study, how the chemical moves through the body and breaks down, and the applicability of the study to humans. Ultimately, health advisories are reflective of sensitive health endpoints (i.e., the adverse effect that occurs at the smallest concentrations). The health advisory levels for PFOA and PFOS were based on a decreased serum anti-tetanus antibody concentration in 7-year-old children receiving the tetanus and diphtheria vaccine. The GenX and PFBS health advisory levels were derived based on critical liver effects in mice and observed hypothyroidism in newborn mice, respectively.

By basing health advisories on sensitive health effects the advisory level is also protective against other potential health effects that may occur at higher levels.

On April 10, 2024, EPA released its final rule setting drinking water standards for six per- and polyfluoroalkyl substances (PFAS). The rule set maximum contaminant levels goals (MCLGs) and maximum contaminant levels (MCLs) for the following six PFAS and their salts: PFOA, PFOS, perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), HFPO-DA, and PFBS.

Individual MCLGs and MCLs were established for PFOA and PFOS, at 0 ppt and 4 ppt respectively. MCLGs are set at 0 ppt based on the EPA’s determination that these compounds are carcinogenic. Three additional MCLGs and MCLs were set for PFHxS, PFNA, and HFPO-DA at 10 ppt each. EPA also established a regulatory requirement for mixtures of PFHxS, PFNA, PFBS, and HFPO-DA.

The rule requires an initial set of monitoring samples to be analyzed and reported to the state by April 2027. The public will be informed about these detections in these samples through the system’s consumer confidence reports (CCRs). Water systems subject to the rule will be required to comply with the MCLs by April 2029. The public will be notified of violations within 30 days and informed through the system’s CCRs. Beginning in 2027 water systems will monitor for PFAS in drinking water on a regular schedule. The results of this monitoring will also be included in water system CCRs.

On May 18, 2026, EPA announced the release of two proposed revisions to the 2024 PFAS rule described above. One rule seeks to rescind the regulatory requirements for the compounds regulated using the hazard index (PFHxS, PFNA, PFBS, and HFPO-DA). The second rule looks to extend the 2029 compliance deadline for PFOA and PFOS standards using a national exemptions framework.

Exemptions allow water systems additional time to achieve compliance with new drinking water regulations under the Safe Drinking Water Act. This rule proposal, if finalized, would allow eligible water systems to request an additional two-year to comply with the PFOA and PFOS MCLs. So those systems that obtain a federal exemption would come into compliance by April 26, 2031.

The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) includes 29 PFAS compounds. EPA’s latest release of UCMR 5 data (January 2026) included results for over 10,000 water systems. Among the 29 PFAS that EPA monitors, 25 have been detected. PFOA and PFOS were detected above their MCL values of 4 ppt each in 8.0% and 8.9% of systems, respectively. HFPO-DA, PFHxS, PFNA, and the Hazard Index mixture of these three PFAS plus PFBS had low rates of detection above their respective MCL values, at roughly 0.03%, 0.7%, 0.1%, and 0.8% respectively.

Contact your public water system to learn more about PFAS testing and results that may be available for your drinking water supply.

PFAS can be found in drinking in homes relying on private wells. If you get your drinking water from a private well, you should regularly sample your water and have the samples analyzed by a certified laboratory. You can find information on how to sample for PFAS and where to send samples for analysis by contacting your state water laboratory certification officer. Contact information for your state can be found at EPA's drinking water lab certification page. Additional information about well water testing from EPA is available on its private drinking water well FAQ page.

If you are concerned about PFAS in your drinking water, you may want to consider purchasing a home treatment device. However, in order to make a well-informed and cost-effective decision, consider checking with your water system or reading your water system’s CCR to learn more about your water system’s source water and treatment systems. Your water system may also be able to help you understand water quality considerations should you want to select a treatment device for PFAS.

 

Importantly, there are independent certifying organizations that ensure home water treatment devices meet contaminant removal claims. Always consider installing certified home water treatment products. NSF International, the Water Quality Association, Underwriters Laboratories and CSA International all certify home treatment products for removal of contaminants. The relevant PFAS removal standard is NSF/ANSI Standards 53 and 58. If you choose to use a home treatment device, it is very important to follow the manufacturer’s operation and maintenance instructions carefully to make sure the device works properly.

Bottled water quality can vary. Bottled water in the United States is regulated by the U.S. Food and Drug Administration and is required to meet standards equal to the EPA’s tap water standards. There are also individual state standards. However, in most cases, you must contact the bottled water manufacturer for information about PFAS levels. EPA is currently not recommending bottled water based solely on concentrations of PFAS exceeding the health advisories.