At a glance
| Chemical family | Per- and polyfluoroalkyl substance (PFAS) — ether-bonded perfluoroalkyl ether carboxylic acid; fluoropolymer manufacturing processing aid; the chemistry-class replacement for PFOA in DuPont/Chemours fluoropolymer production |
| CAS number | 13252-13-6 (HFPO-DA, acid form); 62037-80-3 (HFPO-DA ammonium salt, the manufactured commercial form); trade name "GenX" |
| Classification | Not formally evaluated by IARC as a separate compound; US EPA Final PFAS NPDWR April 2024 established Maximum Contaminant Level at 10 ng/L (10 ppt) for HFPO-DA; HFPO-DA also included in the four-compound Hazard Index (HI ≤ 1, HBV 10 ng/L); US EPA Toxicity Assessment of GenX Chemicals (2021); ECHA REACH Substance of Very High Concern (SVHC) listing July 2019; North Carolina DEQ Consent Order with Chemours 2019 (amended multiple times since) |
| Where you encounter it | Drinking water in regions downstream of Chemours/DuPont fluoropolymer manufacturing facilities (Fayetteville NC, Parkersburg WV, Dordrecht NL); ambient air near fluoropolymer manufacturing sites; surface water and groundwater in contamination zones; trace residuals in finished fluoropolymer products (Teflon, Tedlar, technical films, fluoropolymer membranes); indoor dust in Cape Fear region homes; mixtures with legacy PFOA/PFOS in many PFAS-contaminated sites |
| Sleep micro environment relevance | Indirect but real in contaminated regions. The drinking water and ambient air exposure happens outside the bedroom but contributes to total body burden. Households in active contamination zones see measurable GenX in indoor dust, which is the bedroom-relevant exposure surface. For populations outside contaminated regions, residential GenX exposure is generally below the 10 ng/L MCL |
| Activated carbon capture | Not applicable for VOC-phase capture. For drinking water, both granular activated carbon (GAC) and reverse osmosis (NSF/ANSI 58) are effective for GenX removal; certified residential systems substantially reduce GenX concentrations from contaminated source water. Inferred from established residential PFAS water-treatment performance applied to GenX-specific contamination scenarios |
What it is
GenX — hexafluoropropylene oxide dimer acid (HFPO-DA), CAS 13252-13-6 (acid form), 62037-80-3 (ammonium salt) — is an ether-bonded perfluoroalkyl ether carboxylic acid. It differs from PFOA in two important ways: it contains an ether-oxygen bridge in the perfluoroalkyl chain, and it is shorter overall (a 6-fluorocarbon structure with ether-bridged C3 architecture vs PFOA's 8-fluorocarbon straight chain). DuPont introduced GenX commercially in 2009 as a polymerization processing aid for fluoropolymer manufacturing, replacing APFO (the salt of PFOA) that DuPont was phasing out under the 2006 EPA/industry PFOA Stewardship Program.
GenX is itself a PFAS — all perfluoroalkyl bonds are intact, and the compound shares the environmental persistence that defines the class. The "Gen X" trade name was a marketing reference to the next-generation chemistry, not a designation that the compound is non-PFAS. Human half-life is shorter than PFOA's; the 2021 EPA chronic toxicity assessment supported a low chronic oral reference dose and informed the 2024 federal MCL of 10 ng/L.
Where you encounter it
Drinking water near fluoropolymer manufacturing
The dominant population-level GenX exposure pathway in known-contaminated regions. The Chemours Fayetteville Works plant (formerly DuPont) discharged GenX into the Cape Fear River for an estimated decades before Sun, Arevalo, Strynar, Lindstrom and colleagues at US EPA published the foundational detection paper in Environmental Science & Technology Letters in November 2016. Peer-reviewed — foundational Cape Fear contamination paper The Cape Fear Public Utility Authority serves Wilmington NC and downstream communities — the contaminated water reached approximately 300,000 people through the municipal supply. The Chemours plant in Parkersburg WV (the same historical APFO/PFOA contamination site that generated the original DuPont PFOA litigation) shows similar GenX contamination patterns. The Chemours plant in Dordrecht NL has documented GenX in surrounding surface and drinking water. Outside these documented fluoropolymer-manufacturing zones, GenX in US drinking water is generally below the EPA 10 ng/L MCL, though monitoring under the 2024 federal rule implementation is still expanding.
Ambient air emissions and atmospheric transport
GenX has been measured in air, rainwater, and surface water at substantial distances from manufacturing facilities. Air emissions from the Chemours Fayetteville plant contributed to contamination of the surrounding region not only through direct atmospheric deposition but also via rainwater recharge of groundwater. The Cape Fear regional contamination footprint extends well beyond the Cape Fear River itself partly because of this atmospheric pathway. Air emissions monitoring at Chemours plants has been part of the NC DEQ Consent Order requirements since 2019.
Trace residuals in finished fluoropolymer products
GenX is used as a polymerization processing aid in the manufacture of Teflon, Tedlar, fluoropolymer membranes, and other fluoropolymer products. Trace residual amounts can remain in finished products. The parallel to the historical PFOA-from-Teflon concerns applies in part: the dominant population-level GenX exposure pathway is manufacturing-area water and air, not consumer use of fluoropolymer products. Inferred from the established PFOA exposure-pathway literature; finished-product residual GenX concentrations have not been extensively characterized at the consumer-product level For households outside contaminated regions, consumer fluoropolymer products are not a meaningful GenX exposure source.
Mixtures with legacy PFOA/PFOS
Many PFAS-contaminated sites show GenX in mixtures alongside legacy PFOA, PFOS, and other PFAS — indicating environmental persistence and mobility of all PFAS in groundwater systems. The EPA 2024 Hazard Index regulatory approach for mixed PFAS in drinking water (HI ≤ 1 across HFPO-DA + PFHxS + PFNA + PFBS) explicitly addresses dose-additive effects when multiple PFAS co-occur. In Cape Fear sampling, GenX, PFOA, PFOS, and a longer list of novel PFAS were measured simultaneously, and the regulatory and remediation response treats the mixture rather than single compounds.
Indoor dust in Cape Fear region homes
Indoor dust sampling in homes within the Cape Fear contamination footprint has documented GenX at measurable concentrations, indicating that contaminated outdoor air and water translate to indoor accumulation. For populations outside known-contaminated regions, indoor dust GenX concentrations are generally low or undetectable. The household-dust contribution to total body burden is meaningful only in active contamination zones.
What the research says
The 2016 Cape Fear detection — Sun, Strynar, Lindstrom
The foundational paper was Sun, Arevalo, Strynar, Lindstrom, Richardson, Kearns, Pickett, Smith, and Knappe 2016 in Environmental Science & Technology Letters — "Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina." Peer-reviewed The paper used non-targeted analytical methods to identify a previously unrecognized population of novel PFAS in the Cape Fear River downstream of the Chemours Fayetteville plant. The detection triggered the regulatory cascade that produced the NC DEQ Consent Order (2019), the EPA 2021 toxicity assessment, the 2024 federal MCL, and ongoing multi-billion-dollar litigation.
The EPA 2021 Toxicity Assessment and Conley developmental studies
The EPA Toxicity Assessment of GenX Chemicals (October 2021) established the federal chronic oral RfD at 3 × 10⁻⁶ mg/kg/day based on hepatic effects in mice. Regulatory The 2021 assessment was the technical basis for the 2024 NPDWR MCL of 10 ng/L. Conley, Lambright, Evans and colleagues 2019 in Environmental Science & Technology reported gestational exposure rat studies showing GenX reduces fetal weight and produces placental effects at environmentally relevant oral doses. Peer-reviewed Animal studies consistently document hepatic toxicity from GenX exposure — liver weight increase, hepatocyte hypertrophy, lipid metabolism disruption — at lower doses than PFOA in some comparisons. Cape Fear human epidemiology is emerging but long-latency outcomes have not yet been studied with adequate follow-up time. Inferred from the general PFAS-class epidemiology timeline
The NC DEQ Consent Order and EU REACH SVHC listing
The NC DEQ Consent Order with Chemours entered February 2019 required substantial discharge reduction (Chemours reduced facility GenX discharge by over 99% under the order), on-site treatment installation, off-site water supply remediation for affected users, and ongoing monitoring. Regulatory The order has been amended multiple times since. ECHA listed HFPO-DA on the REACH Candidate List of SVHC in July 2019 on persistent, mobile, and toxic (PMT) grounds. Regulatory HFPO-DA is also covered under the 2023 EU universal PFAS restriction proposal.
The 2024 federal MCL — current regulatory landmark
The April 10, 2024 EPA Final PFAS NPDWR established the HFPO-DA MCL at 10 ng/L. Regulatory GenX is one of only six PFAS with specific federal MCLs (PFOA/PFOS 4 ng/L; PFHxS/PFNA/HFPO-DA 10 ng/L; plus Hazard Index ≤ 1). The 10 ng/L value places GenX among the strictest drinking water standards in the federal inventory. Compliance deadline was originally 2029; EPA proposed modifications and an extension in 2025.
What helps reduce exposure
For drinking water in affected regions: install certified PFAS-removal filtration. Both NSF/ANSI 58 (reverse osmosis) and certain NSF/ANSI 53 (GAC) certified filters are effective for GenX. The certification language matters — verify the specific PFAS-reduction claim and that HFPO-DA is included in the certification scope. For households in the Cape Fear, Parkersburg, or similar contaminated regions, point-of-use reverse osmosis at the kitchen sink is typically the cost-effective intervention.
For municipal water customers: review the annual Consumer Confidence Report (CCR). EPA-regulated public water systems report PFAS results under the 2024 NPDWR implementation. If GenX is detected near or above the 10 ng/L MCL, contact the water utility for current treatment status and the timeline for compliance.
For private well households in contaminated regions: certified laboratory testing is the actionable verification. State environmental agencies in affected states (NC, WV, OH, and others) maintain lists of laboratories certified to analyze GenX and other PFAS at the low-ng/L concentrations relevant to the EPA MCL. State-funded testing programs exist in several affected states for households in defined contamination zones.
Participate in state-level biomonitoring and exposure assessment programs. North Carolina, Ohio, and several other states run blood biomonitoring for affected populations. Participation contributes to the human epidemiology that will eventually inform clinical guidance, and provides individual exposure-burden information that can inform medical follow-up.
For utility-level intervention: advocate for granular activated carbon or anion-exchange treatment at the municipal water plant. The Cape Fear Public Utility Authority installed substantial GAC treatment in response to the contamination, reducing GenX concentrations in delivered water substantially. Utility-level treatment is generally more cost-effective per household than point-of-use filtration, but takes longer to implement and requires customer-base demand to justify the capital investment.
What does NOT help
- "GenX-free" labels without third-party verification. Marketing claims about GenX absence in consumer products are typically not the relevant exposure pathway — the manufacturing-area water and air contamination is the dominant pathway, not consumer product use.
- Assuming non-stick cookware is the main GenX exposure route. Properly used Teflon and other fluoropolymer-coated cookware at recommended temperatures is not the dominant GenX exposure source for general populations. The manufacturing-process contamination is the substantially larger pathway.
- Avoiding all Teflon products as a primary GenX mitigation. The products themselves are not the main exposure route. The mitigation strategy is water filtration in contaminated regions, not category elimination of fluoropolymer products.
- Boiling water. Concentrates rather than removes PFAS including GenX — as water evaporates, PFAS stays in the smaller volume.
- Standard activated carbon pitchers without specific PFAS certification. Variable performance for PFAS reduction. NSF/ANSI 58 or NSF/ANSI 53 with specific PFAS certification language is required for reliable performance.
Open research questions
- Long-term effects of chronic GenX exposure at residential levels — the Cape Fear population is being studied but the long-latency disease outcomes that define the PFOA literature (cancers, cardiovascular disease, fertility) require multi-decade follow-up that has not yet been completed for GenX-specific exposure. Speculation re: long-latency outcomes; established at higher chronic exposures in animal studies
- Reservoir effects in soil, biota, and biosolids downstream of Chemours plants — environmental persistence questions are characterized at the broad PFAS class level but GenX-specific transport and accumulation patterns continue to be studied. Speculation
- Regulatory variation across jurisdictions — EPA 10 ng/L MCL vs European RIVM 18 ng/L vs other national values — and what would drive convergence or divergence over the next regulatory cycle. Inferred from current PFAS regulatory landscape; the convergence timeline is uncertain
- GenX breakdown products and their environmental fate — the parent compound is environmentally persistent, but degradation products and their toxicity have not been fully characterized. Speculation
Citations
- Sun M, Arevalo E, Strynar M, Lindstrom A, Richardson M, Kearns B, Pickett A, Smith C, Knappe DRU (2016). Legacy and emerging perfluoroalkyl substances are important drinking water contaminants in the Cape Fear River Watershed of North Carolina. Environmental Science & Technology Letters, 3(12):415-419. DOI 10.1021/acs.estlett.6b00398 Peer-reviewed — foundational Cape Fear contamination paper
- US Environmental Protection Agency (2024). PFAS National Primary Drinking Water Regulation — Final Rule. Federal Register, 89(82):32532-32757. HFPO-DA MCL 10 ng/L; HFPO-DA also in Hazard Index alongside PFHxS, PFNA, PFBS. federalregister.gov Regulatory
- US Environmental Protection Agency (2021). Human Health Toxicity Assessment for GenX Chemicals. EPA/822/R-21/010. Chronic oral RfD 3 × 10⁻⁶ mg/kg/day based on hepatic effects in mice. epa.gov Regulatory
- Conley JM, Lambright CS, Evans N, Strynar MJ, McCord J, McIntyre BS, Travlos GS, Cardon MC, Medlock-Kakaley E, Hartig PC, Wilson VS, Gray LE Jr (2019). Adverse maternal, fetal, and postnatal effects of hexafluoropropylene oxide dimer acid (GenX) from oral gestational exposure in Sprague-Dawley rats. Environmental Science & Technology, 53(8):4622-4633. DOI 10.1021/acs.est.9b00713 Peer-reviewed — GenX developmental toxicity rat studies
- Strynar M, Dagnino S, McMahen R, Liang S, Lindstrom A, Andersen E, McMillan L, Thurman M, Ferrer I, Ball C (2015). Identification of novel perfluoroalkyl ether carboxylic acids (PFECAs) and sulfonic acids (PFESAs) in natural waters using accurate mass time-of-flight mass spectrometry (TOFMS). Environmental Science & Technology, 49(19):11622-11630. DOI 10.1021/acs.est.5b01215 Peer-reviewed — GenX detection methodology development
- Pan Y, Zhang H, Cui Q, Sheng N, Yeung LWY, Sun Y, Guo Y, Dai J (2018). Worldwide distribution of novel perfluoroether carboxylic and sulfonic acids in surface water. Environmental Science & Technology, 52(14):7621-7629. DOI 10.1021/acs.est.8b00829 Peer-reviewed — GenX environmental occurrence including Chemours Fayetteville
- North Carolina Department of Environmental Quality. Consent Order between NC DEQ, Cape Fear River Watch, and The Chemours Company FC LLC — Bladen County Superior Court (February 2019) and subsequent amendments. deq.nc.gov Regulatory
- European Chemicals Agency (2019). HFPO-DA — included in the REACH Candidate List of Substances of Very High Concern (SVHC), July 2019. Listed on grounds of persistent, mobile, and toxic (PMT) properties. echa.europa.eu/candidate-list Regulatory
- Wang Z, Cousins IT, Scheringer M, Hungerbühler K (2013). Fluorinated alternatives to long-chain perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane sulfonic acids (PFSAs) and their potential precursors. Environment International, 60:242-248. DOI 10.1016/j.envint.2013.08.021 Peer-reviewed — regrettable substitution framing applies to GenX
- US Environmental Protection Agency. Per- and Polyfluoroalkyl Substances (PFAS) — main agency PFAS page covering the 2024 NPDWR including HFPO-DA, the GenX-specific regulatory history, and ongoing PFAS regulatory actions. epa.gov/sdwa/pfas Regulatory
Frequently asked questions
What is GenX chemical?
GenX is the DuPont/Chemours trade name for hexafluoropropylene oxide dimer acid (HFPO-DA), CAS 13252-13-6, and its ammonium salt CAS 62037-80-3. It is a per- and polyfluoroalkyl substance (PFAS) that DuPont introduced in 2009 as a replacement for ammonium perfluorooctanoate (APFO, the salt of PFOA) in fluoropolymer manufacturing. GenX is itself a PFAS — the "next generation" marketing framing referred to it being the replacement chemistry rather than a non-PFAS alternative. The compound is used primarily as a polymerization processing aid in the manufacture of Teflon, Tedlar, and other fluoropolymer products.
Is GenX safer than PFOA?
Mixed. GenX has a shorter biological half-life in humans than PFOA, which limits chronic body burden accumulation at equivalent exposure. But the EPA's 2024 Final PFAS National Primary Drinking Water Regulation established HFPO-DA at an MCL of 10 ng/L — one of only six PFAS with a specific MCL — and that low value reflects EPA's assessment that GenX is potent enough to warrant the same regulatory rigor as PFOA. Some animal studies show GenX produces more hepatic toxicity per dose than PFOA. The "safer" framing was the corporate marketing position when DuPont/Chemours introduced the chemistry in 2009; the 2017 Cape Fear contamination discovery and the subsequent EPA toxicity assessment shifted the regulatory consensus.
Where was GenX contamination found?
The most-cited single GenX contamination case is the Cape Fear River in North Carolina. The Chemours plant in Fayetteville, NC (the former DuPont fluoropolymer manufacturing facility, transferred to Chemours when DuPont spun off its chemicals business in 2015) discharged GenX into the Cape Fear River for years before discovery. Sun, Strynar, Lindstrom and colleagues published the foundational detection paper in Environmental Science & Technology Letters in November 2016, documenting GenX in the Wilmington NC drinking water supply downstream of the plant. The discovery affected hundreds of thousands of people. Subsequent measurement found GenX downstream of the Chemours Parkersburg WV plant (the same historical APFO contamination zone) and at the Chemours Dordrecht plant in the Netherlands. Air emissions extend the contamination footprint substantially beyond direct discharge.
Is GenX in Teflon?
GenX is used as a polymerization processing aid in the manufacture of Teflon and other fluoropolymer products, not as a permanent ingredient in the finished product. Residual amounts of GenX can remain in finished fluoropolymer products at low concentrations, but the dominant GenX exposure pathway is not consumer use of Teflon-coated cookware — it is contaminated drinking water and ambient air near manufacturing facilities. The parallel to the historical PFOA-from-Teflon concerns applies: the manufacturing process and the manufacturing site contamination produced the population-level exposure, not the finished product use in households. Properly used Teflon cookware at recommended temperatures is not the main GenX exposure source for general populations.
What is the EPA limit for GenX?
The US EPA's April 10, 2024 Final PFAS National Primary Drinking Water Regulation established the Maximum Contaminant Level (MCL) for HFPO-DA (GenX) at 10 nanograms per liter (ng/L), also expressed as 10 parts per trillion (ppt). GenX is one of only six PFAS with specific federal MCLs: PFOA and PFOS at 4 ng/L each; PFHxS, PFNA, and HFPO-DA at 10 ng/L each; and the mixture Hazard Index at HI ≤ 1 (which includes HFPO-DA alongside PFHxS, PFNA, and PFBS). The 10 ng/L MCL for GenX is among the lowest PFAS-specific drinking water standards established globally. Public water systems have until 2029 to comply with the rule under the originally finalized timeline; EPA proposed modifications and a compliance deadline extension in 2025 that the agency may finalize.
Is GenX in drinking water?
Yes in contaminated regions, particularly near fluoropolymer manufacturing facilities. The Cape Fear River watershed in North Carolina (downstream of the Chemours Fayetteville plant) has been the most-characterized contamination zone since the 2017 discovery, affecting Wilmington and other downstream municipal water systems serving hundreds of thousands of people. The Chemours Parkersburg WV plant area has similar contamination. Sampling near the Chemours Dordrecht NL plant has documented GenX in surface water and drinking water. Outside fluoropolymer manufacturing areas, GenX concentrations in US drinking water systems are generally below the EPA 10 ng/L MCL, though monitoring is still expanding under the 2024 federal rule implementation.
What happened in the Cape Fear River?
The Chemours Fayetteville Works plant (the former DuPont fluoropolymer manufacturing facility, transferred to Chemours in 2015) discharged GenX (HFPO-DA) and other novel PFAS into the Cape Fear River and the adjacent atmosphere over many years before discovery. Sun, Strynar, Lindstrom and colleagues at US EPA published the detection in Environmental Science & Technology Letters in November 2016, documenting GenX in the Wilmington NC drinking water supply (Cape Fear Public Utility Authority). The discovery triggered substantial state-level regulatory action. The North Carolina Department of Environmental Quality (NC DEQ) entered into a Consent Order with Chemours in February 2019 requiring substantial discharge reduction, on-site treatment, off-site water supply remediation for affected residential and commercial users, and ongoing monitoring. The Consent Order has been amended multiple times since. Multi-billion-dollar lawsuits by affected utilities, states, and class-action plaintiffs are active and produced multi-billion-dollar settlements 2023-2024.
Related compounds
Embr Sleep is a sleep environment company researching the chemistry of the bedroom. See the methodology page for how this Atlas tags claims by evidence strength. For broader context on PFAS exposure pathways and firefighter take-home contamination, see non-toxic bedroom and farm family sleep.
Last reviewed 2026-05-25. If you find a factual error, contact us.