EPA legal limit
4 ppt
Maximum Contaminant Level
EWG health guideline
0.004 ppt
Science-based, stricter target
IARC classification
Group 2B
Cancer research classification
Health effects
PFOA is classified as a probable human carcinogen (IARC Group 2A; NTP: reasonably anticipated to be a human carcinogen). Documented associations include kidney cancer, testicular cancer, thyroid disease, ulcerative colitis, elevated cholesterol, pregnancy-induced hypertension, reduced vaccine response in children, and adverse birth outcomes including low birth weight and preterm delivery. PFOA bioaccumulates in blood, liver, and breast milk, with a human serum half-life of approximately 3.5 years — meaning a single exposure persists for years. The EWG health guideline of 0.004 ppt is 1,000 times stricter than the 4 ppt EPA MCL because no safe threshold has been established for carcinogens. Both EPA and NTP classifications are based on epidemiological evidence and animal carcinogenicity data.
Where it comes from
Primary industrial source: DuPont and Chemours fluoropolymer manufacturing, most notably at the Washington Works plant in Parkersburg, West Virginia, and along the Cape Fear River in North Carolina where GenX contamination brought national attention to legacy PFOA discharge. Secondary source: aqueous film-forming foam (AFFF) used at military bases and civilian airports, where decades of fire-suppression training have created significant groundwater plumes. Consumer pathways include residue from non-stick cookware (Teflon), grease-resistant food packaging such as pizza boxes and microwave popcorn bags, and stain-resistant coatings on carpets and clothing. PFOA persists in groundwater for decades after contamination ends and has been detected in remote environments and rainwater due to atmospheric long-range transport.
How it's regulated
EPA issued the first-ever federal PFOA limit — a Maximum Contaminant Level of 4 ppt — on April 10, 2024, under the Safe Drinking Water Act PFAS National Primary Drinking Water Rule. Water systems detecting PFOA above 16 ppt must notify the public immediately; all systems exceeding 4 ppt must reduce levels to compliance by April 2026. The EWG health guideline is 0.004 ppt — 0.4% of the legal limit — derived from a carcinogen risk model with no safe threshold. Prior to 2024, the only federal benchmark was a non-enforceable EPA Lifetime Health Advisory of 70 ppt (2016), tightened to 0.004 ppt in 2022 before the binding MCL was finalised. UCMR5 national monitoring (2023–2025) produced the first comprehensive dataset of PFOA detection across U.S. public water systems.
The EPA vs EWG gap
The legal limit (4 ppt) is 1000× higher than the EWG health guideline (0.004 ppt). Water can be legally compliant while still exceeding the science-based threshold.
How to filter pfoa
Not all filters address pfoa. Look for independently certified filters — NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is pfoa?
PFOA is a long-chain, 8-carbon per- and polyfluoroalkyl substance (PFAS) classified by IARC as a Group 2A probable human carcinogen. First regulated by EPA in April 2024 at 4 ppt under the Safe Drinking Water Act PFAS rule, it is found in non-stick manufacturing effluent, AFFF firefighting foam, and contaminated groundwater, and is both persistent and bioaccumulative.
What are the health effects of pfoa?
PFOA is classified as a probable human carcinogen (IARC Group 2A; NTP: reasonably anticipated to be a human carcinogen). Documented associations include kidney cancer, testicular cancer, thyroid disease, ulcerative colitis, elevated cholesterol, pregnancy-induced hypertension, reduced vaccine response in children, and adverse birth outcomes including low birth weight and preterm delivery. PFOA bioaccumulates in blood, liver, and breast milk, with a human serum half-life of approximately 3.5 years — meaning a single exposure persists for years. The EWG health guideline of 0.004 ppt is 1,000 times stricter than the 4 ppt EPA MCL because no safe threshold has been established for carcinogens. Both EPA and NTP classifications are based on epidemiological evidence and animal carcinogenicity data.
Is pfoa regulated in drinking water?
EPA issued the first-ever federal PFOA limit — a Maximum Contaminant Level of 4 ppt — on April 10, 2024, under the Safe Drinking Water Act PFAS National Primary Drinking Water Rule. Water systems detecting PFOA above 16 ppt must notify the public immediately; all systems exceeding 4 ppt must reduce levels to compliance by April 2026. The EWG health guideline is 0.004 ppt — 0.4% of the legal limit — derived from a carcinogen risk model with no safe threshold. Prior to 2024, the only federal benchmark was a non-enforceable EPA Lifetime Health Advisory of 70 ppt (2016), tightened to 0.004 ppt in 2022 before the binding MCL was finalised. UCMR5 national monitoring (2023–2025) produced the first comprehensive dataset of PFOA detection across U.S. public water systems.
Where does pfoa come from?
Primary industrial source: DuPont and Chemours fluoropolymer manufacturing, most notably at the Washington Works plant in Parkersburg, West Virginia, and along the Cape Fear River in North Carolina where GenX contamination brought national attention to legacy PFOA discharge. Secondary source: aqueous film-forming foam (AFFF) used at military bases and civilian airports, where decades of fire-suppression training have created significant groundwater plumes. Consumer pathways include residue from non-stick cookware (Teflon), grease-resistant food packaging such as pizza boxes and microwave popcorn bags, and stain-resistant coatings on carpets and clothing. PFOA persists in groundwater for decades after contamination ends and has been detected in remote environments and rainwater due to atmospheric long-range transport.
How do I remove pfoa from tap water?
The most effective methods for removing pfoa are: Reverse osmosis (RO), NSF 58 certified RO system, Activated carbon block filter, NSF 53 certified filter. Look for NSF-certified systems — independent certification confirms removal claims have been verified.
Is pfoa in your water?
Enter your ZIP code to see the measured level in your specific utility.