Drinking water guide
PFAS in Drinking Water: What You Need to Know
A comprehensive guide to "forever chemicals" - what they are, how they enter water supplies, what the federal limits mean, and what you can do about them.
Key Takeaway
PFAS are synthetic chemicals that do not break down in the environment or the body. EPA's UCMR5 program tested 143,000+ water systems and found widespread detections. The 2024 federal rule set the first-ever enforceable limits for PFOA and PFOS at 4 parts per trillion, near the detection threshold. Water systems must comply by 2029. If your water has PFAS detections, a certified reverse osmosis filter is the most effective household protection.
What PFAS Are and Why They Matter
Per- and polyfluoroalkyl substances (PFAS) are a group of over 12,000 man-made chemicals that have been manufactured since the 1940s. They share an extremely strong carbon-fluorine bond, one of the strongest in chemistry, that makes them resistant to heat, water, oil, and biological degradation.
This resistance is what made PFAS useful in products like Teflon, Gore-Tex, Scotchgard, and aqueous film-forming firefighting foam (AFFF). It is also what makes them an environmental and health concern: once released, PFAS do not meaningfully break down in soil, water, or living organisms. They accumulate in the food chain and in human tissue over decades. Studies have detected PFAS in the blood of approximately 98% of Americans tested.
The two most-studied compounds, PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) - were phased out by major manufacturers in the early 2000s after research linked them to health effects. However, they persist in the environment for decades after production stops. Newer "short-chain" PFAS replacements are now also under scrutiny.
How PFAS Contaminates Drinking Water
PFAS contamination of drinking water comes from several well-documented sources:
- Military bases and airports. Decades of AFFF firefighting foam use during training exercises and emergency responses contaminated groundwater at hundreds of military installations and civilian airports. These are the largest single-source contamination sites in the country.
- Industrial manufacturing. Facilities that manufactured or used PFAS-containing products have discharged these chemicals into waterways and groundwater. Major contamination sites include former DuPont and 3M plants.
- Landfills. Consumer products containing PFAS, food packaging, clothing, carpet, electronics, end up in landfills. Leachate from these sites carries PFAS into surrounding groundwater.
- Biosolids (sewage sludge). Treated sewage sludge applied as fertilizer on agricultural land can contain elevated PFAS concentrations. These leach into wells and surface water, contaminating both drinking water and food crops.
- Wastewater discharge. Municipal wastewater treatment plants are not designed to remove PFAS. What goes into the sewer, from industrial users, carpet cleaning, and consumer products, passes through treatment and is discharged to rivers that serve as drinking water sources downstream.
Once PFAS reaches groundwater, it migrates slowly through aquifers and is extraordinarily expensive to remediate. Cleanup costs at known contamination sites run into billions of dollars. Browse PFAS detection rates by state to see where contamination is most prevalent.
The UCMR5 Testing Program
EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR5) is the most comprehensive national PFAS screening of drinking water ever conducted. Between 2023 and 2025, water systems serving more than 10,000 people, plus a representative sample of smaller systems, were required to test for 29 PFAS compounds and lithium.
The program generated approximately 1.93 million individual test results, which PlainWater makes searchable. Key compounds monitored include:
| Compound | 2024 MCL | Significance |
|---|---|---|
| PFOA | 4 ppt | Most-studied long-chain PFAS; linked to cancer, immune effects |
| PFOS | 4 ppt | Major AFFF component; persistent in blood for years |
| PFNA, PFHxS, HFPO-DA, PFBS | Hazard Index ≤ 1 | Mixture of emerging PFAS; combined limit based on additive toxicity |
Use PlainWater to search UCMR5 results for your water system, county, or state.
The 2024 Federal Drinking Water Rule
In April 2024, EPA finalized the first-ever National Primary Drinking Water Regulation for PFAS. At 4 parts per trillion, the PFOA and PFOS limits are set near the current laboratory detection threshold, reflecting EPA's conclusion that there is effectively no safe level of exposure for these compounds.
The timeline for compliance:
- By 2027: Water systems must complete initial PFAS monitoring
- By 2029: Systems exceeding MCLs must have treatment in place
- Ongoing: Quarterly monitoring for systems with detections
EPA estimates that water systems serving approximately 100 million Americans will need to install PFAS treatment to comply. The federal government has allocated $9 billion through the Bipartisan Infrastructure Law to help systems fund treatment upgrades.
Health Concerns: What the Research Shows
PFAS health research is evolving rapidly, but several associations have been consistently documented across multiple studies:
- Cancer: PFOA is classified as a possible carcinogen by the International Agency for Research on Cancer (IARC). Studies have found elevated rates of kidney and testicular cancer in communities with high PFAS exposure.
- Immune effects: PFAS exposure has been associated with decreased vaccine antibody response, a finding that has been replicated across multiple populations, including children.
- Thyroid disease: Several studies link PFAS exposure to thyroid hormone disruption and increased rates of thyroid disease.
- Pregnancy complications: Research associates PFAS with pregnancy-induced hypertension, pre-eclampsia, and reduced birth weight.
- Cholesterol and liver: Even at relatively low exposure levels, PFAS has been associated with increased total cholesterol and changes in liver enzymes.
The 2022 National Academies of Sciences report recommended clinical exposure assessments for people with blood PFAS levels above certain thresholds, including monitoring for thyroid disease, lipid disorders, and certain cancers.
How to Check Your Water for PFAS
Follow this process to determine your PFAS exposure through drinking water:
- Identify your water system. Check your water bill for the utility name or search PlainWater by county.
- Check UCMR5 results. Search for your system on PlainWater. If it was tested under UCMR5, you will see results for 29 PFAS compounds with detected levels and whether they exceed the 2024 MCL.
- Check your state's data. Some states have conducted their own PFAS testing programs beyond UCMR5, especially Michigan, New Jersey, New Hampshire, and North Carolina, which began testing years before the federal program.
- Request results from your utility. Contact your water utility directly and ask about PFAS testing results. Some systems have tested voluntarily even if not required under UCMR5.
- Consider independent testing. If your system was not tested and you live near a known contamination source (military base, airport, industrial facility), you can send a water sample to a certified laboratory. PFAS testing typically costs $200-400.
Filtration Options That Work
If PFAS has been detected in your water system, household filtration can reduce your exposure while waiting for the utility to install treatment (required by 2029).
Reverse Osmosis (RO)
Most effective. Removes 90-99% of PFAS including short-chain compounds. Under-sink or countertop systems. Look for NSF/ANSI Standard 58 certification.
Cost: $150-500 for point-of-use. Generates waste water.
Granular Activated Carbon (GAC)
Effective for longer-chain PFAS (PFOA, PFOS). Less effective for short-chain compounds. Available as faucet-mounted or under-sink. Look for NSF/ANSI Standard 53 certification.
Cost: $20-200. Requires regular filter replacement.
Important: Do NOT boil water to remove PFAS. Boiling evaporates water but leaves PFAS behind, actually concentrating the contamination. Standard pitcher filters (Brita, PUR) are not certified to remove PFAS unless specifically labeled.
Frequently Asked Questions
What exactly are PFAS "forever chemicals"?
PFAS (per- and polyfluoroalkyl substances) are a family of over 12,000 synthetic chemicals that share an extremely strong carbon-fluorine bond. This bond makes them resistant to heat, water, oil, and biological breakdown, which is why they were used in non-stick coatings, waterproof fabrics, firefighting foam, and food packaging. The same durability that makes them useful makes them nearly impossible to break down in the environment or the human body. They accumulate over time, which is why they are called "forever chemicals."
How does PFAS get into my drinking water?
PFAS enters water supplies through multiple pathways. The most significant sources are: military and airport firefighting foam (AFFF) that has contaminated groundwater at hundreds of sites; industrial discharges from facilities that manufacture or use PFAS-containing products; landfill leachate from consumer products containing PFAS; and agricultural runoff from biosolids (treated sewage sludge) applied to farmland. Once PFAS reaches groundwater, it migrates slowly through aquifers and is extremely difficult to remove.
What are the new EPA limits for PFAS?
In April 2024, EPA set the first-ever enforceable drinking water limits for PFAS: 4 parts per trillion (ppt) for PFOA and 4 ppt for PFOS individually, plus a combined Hazard Index limit of 1 for a group including PFNA, PFHxS, HFPO-DA (GenX), and PFBS. These are among the strictest drinking water standards ever set, 4 ppt is near the current laboratory detection limit. Water systems have until 2027 to begin monitoring and until 2029 to comply. As of May 2026, EPA has proposed (not yet final) rescinding the Hazard Index rule for the four non-PFOA/PFOS compounds and extending the PFOA/PFOS deadline to 2031 for systems that apply; the 4 ppt PFOA/PFOS limits themselves are not proposed to change.
What health effects are linked to PFAS?
Research is ongoing, but studies, including the 2022 National Academies of Sciences report, have associated PFAS exposure with: increased cholesterol, changes in liver enzymes, decreased vaccine antibody response, thyroid disease, pregnancy-induced hypertension and pre-eclampsia, and increased risk of kidney and testicular cancer. Children and pregnant women are considered especially vulnerable. The EPA's 2024 MCL rule cited these effects in setting the 4 ppt limit for PFOA and PFOS.
How can I check if PFAS is in my water?
Search PlainWater's PFAS tracker or your water system page. Under UCMR5, large water systems (serving 10,000+ people) and a sample of smaller systems tested for 29 PFAS compounds between 2023 and 2025. Results are available through PlainWater by system, county, and state. If your system was not tested under UCMR5, check your utility's website for any voluntary PFAS testing results, or contact them directly to ask.
What type of water filter removes PFAS?
The most effective household options are: (1) Reverse osmosis (RO) systems certified to NSF/ANSI Standard 58, these remove the broadest range of PFAS including short-chain compounds. (2) Activated carbon filters certified to NSF/ANSI Standard 53, effective for many PFAS, especially longer-chain compounds, but less effective for some short-chain PFAS. Standard pitcher filters (Brita, PUR) are NOT certified to remove PFAS unless specifically labeled as such. Do not boil water to remove PFAS, boiling concentrates rather than removes these chemicals.
My water system detected PFAS but below the new limits, should I worry?
Any detection of PFAS is worth monitoring, but levels below the 2024 MCLs mean your system currently meets federal standards. The EPA set the PFOA/PFOS limit at 4 ppt based on a determination that there is effectively no safe level, so any detection carries some theoretical risk, particularly with lifetime exposure. If you are concerned, a certified RO filter provides an additional layer of protection. If you are pregnant or have infants, extra caution is reasonable even at sub-MCL levels.
Sources
- U.S. EPA, PFAS National Primary Drinking Water Regulation (April 2024)
- U.S. EPA, Fifth Unregulated Contaminant Monitoring Rule (UCMR5), 2023-2025
- National Academies of Sciences, Engineering, and Medicine, Guidance on PFAS Exposure, Testing, and Clinical Follow-Up (2022)
- International Agency for Research on Cancer (IARC) - PFOA Classification
- U.S. EPA, Drinking Water Health Advisories for PFAS
- NSF International, Drinking Water Treatment Standards (Standards 53 and 58)
- PlainWater, 1.93 million UCMR5 PFAS test results from 143,000+ water systems
This content is for informational purposes only. If you have health concerns related to PFAS exposure, consult your physician. If you have concerns about your drinking water, contact your water utility or state drinking water program.