PFHpA in the Bedroom

At a glance

What it is

PFHpA — perfluoroheptanoic acid, CAS 375-85-9 — is the 7-carbon perfluoroalkyl carboxylic acid. Structurally, PFHpA is identical to PFHxA except for one additional perfluorinated carbon (C7 vs C6), and identical to PFOA except for one fewer perfluorinated carbon (C7 vs C8). The chain-length-versus-properties relationship across the perfluoroalkyl carboxylate spectrum is reasonably smooth: half-life, lipophilicity, and bioaccumulation potential all increase with chain length; PFHpA sits between its neighbors on these axes.

PFHpA has not been a major commercial fluorochemical in its own right. The compound has historically appeared in environmental matrices as an impurity in PFOA-precursor manufacturing, as a co-emission from fluoropolymer plants alongside PFOA, and as an environmental degradation product of certain fluorotelomer precursors. The result is that PFHpA shows up consistently in PFAS-contaminated water — not as a primary contaminant but as part of the characteristic mixed-source signature that defines fluoropolymer-manufacturing or AFFF-impacted contamination zones. The biological half-life in humans is intermediate between PFHxA (~32-42 days) and PFOA (~2-3+ years); precise PFHpA values are less well-characterized than for the neighboring chain lengths because PFHpA has not been a primary research target.

Where you encounter it

From drinking water as PFOA co-contaminant

The dominant population-level PFHpA exposure pathway. The "mixed PFAS signature" in fluoropolymer-impacted water — PFOA dominant, PFHpA at lower but characteristic concentrations alongside it — is a pattern that has been documented across the major US PFAS contamination zones. Hu, Andrews, Lindstrom and colleagues 2016 in Environmental Science & Technology Letters conducted the foundational analysis of PFAS occurrence in US drinking water under EPA's third Unregulated Contaminant Monitoring Rule (UCMR 3), documenting PFHpA at hundreds of US public water systems alongside PFOA, PFOS, and other perfluoroalkyl acids. Peer-reviewed The Cape Fear NC, mid-Ohio River Valley (Parkersburg WV downstream), Cottage Grove MN, and Decatur AL regions show PFHpA at the higher end of the distribution.

From historical fluoropolymer manufacturing

DuPont/Chemours's historical APFO/PFOA manufacturing chemistry produced PFHpA as an impurity in the C8 process feedstock and as a co-emission during fluoropolymer polymerization. The Chemours Fayetteville NC plant has been documented to discharge PFHpA along with PFOA, HFPO-DA (GenX), and other PFAS. The 3M Cottage Grove MN and Decatur AL plants have similar historical signatures. The contamination footprint extends downstream and into ambient air around these facilities. Even after the 2006-2015 PFOA Stewardship Program eliminated long-chain PFAS from US manufacturing, the historical contamination persists in groundwater and surface water systems.

From AFFF firefighting foam degradation

Aqueous Film-Forming Foam (AFFF) used at fire training facilities historically contained C6-C8 fluorotelomer chemistry that degrades in environment to mixtures of perfluoroalkyl acids including PFHpA. The training-area soil and groundwater contamination at military bases, civilian airports, and fire academies shows PFHpA as part of the broader PFAS contamination signature alongside PFOA, PFOS, PFHxS, and others. Communities served by water sourced near AFFF-impacted sites show PFHpA in routine monitoring.

From EPA UCMR 5 monitoring

EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5) requires all US public water systems serving 3,300+ people, plus a representative subset of smaller systems, to sample for 29 PFAS plus lithium between 2023 and 2025. Regulatory PFHpA is among the 29 PFAS monitored. The UCMR 5 published results provide the most comprehensive national PFAS occurrence dataset currently available and are the technical basis EPA will use for the next round of PFAS regulatory prioritization. PFHpA detection rates and concentration distributions in UCMR 5 will inform whether PFHpA enters the federal regulatory framework in a future NPDWR amendment.

From food packaging and indoor dust

Food packaging migration contributes low-level PFHpA exposure as residual or impurity from PFOA-precursor chemistry historically used for grease-resistance applications. Indoor dust accumulates PFHpA at low concentrations from textile treatments and fluorotelomer breakdown products. These pathways are smaller than drinking water contamination for affected-area populations but contribute to total population-level exposure.

What the research says

Hepatic and class-level effects

Animal toxicology of PFHpA shows hepatic effects consistent with the broader PFAS class — liver weight increase, hepatocyte hypertrophy, lipid metabolism effects — at chronic exposure doses. The PFHpA-specific toxicology literature is thinner than for PFOA or PFOS because PFHpA has not been a major direct industrial compound and has not received the research attention that the dominant commercial PFAS have. Most human disease-association studies have included PFHpA in PFAS-mixture analyses rather than studied it as a single compound, which limits the strength of single-compound dose-response conclusions. Inferred from the broader PFAS-class toxicology literature; PFHpA-specific single-compound studies are sparse compared to PFOA

UCMR 3 and UCMR 5 occurrence data

The Hu, Andrews, Lindstrom 2016 paper analyzed EPA UCMR 3 data (sampling 2013-2015) to document PFAS occurrence across US public water systems, including PFHpA. Hu et al. 2016. Peer-reviewed The UCMR 3 dataset established the baseline for understanding national PFHpA distribution prior to PFOA phase-out impacts. UCMR 5 (sampling 2023-2025) is updating the national PFHpA occurrence picture nearly a decade later. Comparison of UCMR 3 and UCMR 5 results will reveal whether the PFOA Stewardship Program reduced PFHpA in source waters or whether environmental persistence has maintained the historical contamination footprint.

Sources, mobility, and pathways

Sunderland, Hu, Dassuncao and colleagues 2019 in Journal of Exposure Science & Environmental Epidemiology published the foundational review of PFAS sources, mobility, and exposure pathways in US populations. Peer-reviewed The review covers PFHpA in the broader context of PFAS-class environmental fate and transport, including the co-occurrence patterns that make PFHpA a useful signature compound for source identification.

Regulatory landscape — federal gap, state coverage

PFHpA is NOT in the US EPA's April 2024 Final PFAS National Primary Drinking Water Regulation. Regulatory It is not among the six PFAS with individual MCLs (PFOA, PFOS, PFHxS, PFNA, HFPO-DA each have specific MCLs) and is not part of the four-compound Hazard Index (PFHxS, PFNA, HFPO-DA, PFBS). UCMR 5 monitoring (2023-2025) is the federal data-generation activity for PFHpA — it does not establish enforceable limits but informs future rulemaking. Several states have included PFHpA in state-level PFAS monitoring requirements or advisory programs: Vermont, New Jersey, and others have addressed PFHpA as part of broader PFAS regulatory frameworks. The ATSDR Toxicological Profile for Perfluoroalkyls covers PFHpA as part of the broader perfluoroalkyl acid assessment. Regulatory

Human epidemiology — emerging

PFHpA human epidemiology is one of the less-developed PFAS sub-literatures. Disease-association studies have generally included PFHpA in PFAS-mixture analyses rather than studied it as a single compound, which limits standalone dose-response conclusions. Population biomonitoring (CDC NHANES) detects PFHpA in US adult serum at lower concentrations than PFOA, PFOS, or PFHxS but consistently above detection limits. The next several years of UCMR 5 occurrence analysis combined with the ongoing PFAS-class epidemiology will likely produce the first PFHpA-specific dose-response characterizations at population scale. Speculation re: timeline for PFHpA-specific dose-response characterization

What helps reduce exposure

For drinking water in affected areas: install certified PFAS-removal filtration. The same NSF/ANSI 58 (reverse osmosis) and NSF/ANSI 53 (PFAS-certified) filters that handle PFOA handle PFHpA — water treatment for PFAS reduction targets the broader perfluoroalkyl acid class rather than single compounds.

Check your utility's UCMR 5 monitoring results. EPA publishes UCMR 5 data through the agency's Consumer Confidence Reports framework and online dashboards as monitoring proceeds 2023-2025. If your water system has detectable PFHpA, the result is typically in the same range as co-occurring PFOA — and the filtration technology that addresses PFOA addresses PFHpA simultaneously.

For firefighters and households near AFFF training sites: enforce the take-home contamination protocol. Same protocol as for the broader PFAS class — change at the station, store contaminated gear outside bedrooms, wash work clothing separately. Advocate department-level transitions to fluorine-free firefighting foams.

HEPA-vacuum carpets and upholstery weekly. Indoor dust contributes low-level PFHpA exposure in homes with treated textile inventory. Standard PFAS dust mitigation reduces the contribution.

What does NOT help

• "PFOA-free" labels. Don't address PFHpA. The PFOA Stewardship Program eliminated PFOA from new manufacturing but did not address PFHpA specifically.
• Generic activated carbon water filters without certification. Variable PFAS-reduction performance. Specific NSF/ANSI 53 certification for PFAS or NSF/ANSI 58 reverse osmosis is required for reliable PFHpA reduction.
• Assuming UCMR 5 monitoring includes all PFAS. The rule covers 29 specific PFAS plus lithium. PFHpA is included, but many other PFAS are not.
• Boiling water. Concentrates rather than removes PFAS.

Open research questions

• PFHpA-specific dose-response curves — most studies aggregate with other perfluoroalkyl acids, which limits standalone conclusions. Speculation re: timeline for standalone characterization
• Biological half-life refinement in humans — the precise value falls between PFHxA and PFOA, but PFHpA-specific pharmacokinetic studies are limited compared to neighboring chain lengths. Inferred from chain-length pharmacokinetic patterns; PFHpA-specific values less well-characterized
• UCMR 5 monitoring results and what they reveal about national PFHpA distribution — UCMR 5 sampling proceeds 2023-2025; comprehensive analysis is anticipated 2025-2026. Speculation re: occurrence patterns; established for UCMR 3 baseline
• Federal regulatory action timeline — UCMR 5 data analysis will inform the next round of EPA PFAS rulemaking; PFHpA inclusion in a future NPDWR amendment is plausible but not assured. Inferred from EPA PFAS prioritization framework

Citations

1. US Environmental Protection Agency (2024). PFAS National Primary Drinking Water Regulation — Final Rule. Federal Register, 89(82):32532-32757. Note: PFHpA NOT in Hazard Index or individual MCLs. federalregister.gov Regulatory
2. US Environmental Protection Agency. Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) — covers 29 PFAS plus lithium, sampling 2023-2025; PFHpA is included. epa.gov/dwucmr Regulatory
3. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Perfluoroalkyls — PFHpA coverage. atsdr.cdc.gov/ToxProfiles/tp200.pdf Regulatory
4. Hu XC, Andrews DQ, Lindstrom AB, Bruton TA, Schaider LA, Grandjean P, Lohmann R, Carignan CC, Blum A, Balan SA, Higgins CP, Sunderland EM (2016). Detection of poly- and perfluoroalkyl substances (PFASs) in U.S. drinking water linked to industrial sites, military fire training areas, and wastewater treatment plants. Environmental Science & Technology Letters, 3(10):344-350. DOI 10.1021/acs.estlett.6b00260 Peer-reviewed — foundational UCMR 3 analysis covering PFHpA
5. Sunderland EM, Hu XC, Dassuncao C, Tokranov AK, Wagner CC, Allen JG (2019). A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects. Journal of Exposure Science & Environmental Epidemiology, 29(2):131-147. DOI 10.1038/s41370-018-0094-1 Peer-reviewed — PFAS sources, mobility, and pathways review
6. Cousins IT, Vestergren R, Wang Z, Scheringer M, McLachlan MS (2016). The precautionary principle and chemicals management: The example of perfluoroalkyl acids in groundwater. Environment International, 94:331-340. DOI 10.1016/j.envint.2016.04.044 Peer-reviewed
7. 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
8. Interstate Technology and Regulatory Council (ITRC) PFAS Team. PFAS Technical and Regulatory Guidance Document. pfas-1.itrcweb.org Regulatory — multi-state regulatory consortium covers PFHpA in PFAS class analysis
9. Vermont Department of Health. PFAS in Drinking Water — state-level advisory values including PFHpA in monitoring framework. healthvermont.gov Regulatory — state-level coverage
10. US Environmental Protection Agency. Per- and Polyfluoroalkyl Substances (PFAS) — main agency PFAS page including UCMR 5 and ongoing regulatory prioritization. epa.gov/sdwa/pfas Regulatory

Frequently asked questions

• What is PFHpA?

  PFHpA — perfluoroheptanoic acid, CAS 375-85-9 — is a 7-carbon perfluoroalkyl carboxylate sitting between PFHxA (C6) and PFOA (C8) in the alkyl carboxylate spectrum. PFHpA has been less prominent as a direct industrial chemical than its neighbors but appears widely in environmental monitoring data as a co-contaminant alongside PFOA. The compound has been included in EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5) sampling program 2023-2025 at hundreds of US public water systems, providing the most comprehensive PFHpA occurrence dataset currently available.

• Is PFHpA regulated by the EPA?

  PFHpA is NOT in the EPA April 2024 Final PFAS National Primary Drinking Water Regulation — no individual MCL, not part of the four-compound Hazard Index. EPA's UCMR 5 (Unregulated Contaminant Monitoring Rule, fifth iteration) includes PFHpA in the monitored substance list, with public water system sampling running 2023-2025. UCMR monitoring informs future federal regulatory action rather than establishing current enforceable limits. Several states (Vermont, New Jersey, others) have included PFHpA in state-level PFAS monitoring requirements or advisory programs. Federal regulatory action for PFHpA is plausibly the next phase of EPA PFAS rulemaking but the timeline is uncertain.

• Where does PFHpA come from?

  PFHpA appears in environmental matrices primarily as a co-contaminant with PFOA rather than as a primary industrial compound. Historical fluoropolymer manufacturing (DuPont/Chemours Parkersburg WV plant area; 3M Cottage Grove MN and Decatur AL) produced PFHpA as an impurity or co-emission alongside PFOA. AFFF firefighting foam degradation contributes to PFHpA in groundwater near training sites. Some fluorotelomer breakdown pathways yield PFHpA among mixed products. The "mixed PFAS signature" in contaminated drinking water — PFOA dominant, PFHpA at lower but characteristic concentrations — is one of the typical patterns that environmental analytical chemists use to identify likely contamination source categories.

• Is PFHpA in drinking water?

  Yes, in many US drinking water systems — most commonly as a co-contaminant alongside PFOA. EPA's UCMR 5 monitoring program (2023-2025) is generating the most comprehensive PFHpA occurrence dataset, sampling at all US public water systems serving 3,300+ people plus a representative subset of smaller systems. Public results published as the monitoring proceeds have documented PFHpA at detectable concentrations in a substantial fraction of sampled systems, generally at lower concentrations than co-occurring PFOA. The Cape Fear North Carolina, mid-Ohio River Valley (Parkersburg WV downstream), and Cottage Grove Minnesota regions show PFHpA at the higher end of the distribution.

• How is PFHpA different from PFOA?

  PFHpA and PFOA are structural neighbors in the perfluoroalkyl carboxylic acid family — PFHpA is the C7 (seven perfluorinated carbons), PFOA is the C8 (eight). Both share the carboxylate head group and the C–F bond chemistry that makes the entire PFAS class environmentally persistent. The chain-length difference produces some toxicokinetic differences: PFHpA has a shorter biological half-life in humans than PFOA, though the precise PFHpA value is less well-characterized than PFOA's well-established 2-3+ year half-life. The regulatory difference matters most: PFOA has the lowest federal MCL of any PFAS (4 ng/L), while PFHpA has no federal MCL and is not in the Hazard Index. In contamination zones the two typically co-occur; remediation that addresses PFOA addresses PFHpA simultaneously.

• What is UCMR 5?

  UCMR 5 is the fifth iteration of the EPA Unregulated Contaminant Monitoring Rule. The Safe Drinking Water Act requires EPA to issue a list of up to 30 unregulated contaminants every 5 years for monitoring by public water systems, with the monitoring data informing future regulatory decisions. UCMR 5 targets 29 PFAS plus lithium for monitoring across 2023-2025. PFHpA is among the 29 PFAS monitored. The rule requires all public water systems serving 3,300+ people to sample, plus a representative subset of smaller systems. The published UCMR 5 results provide the highest-resolution national PFAS occurrence dataset currently available and are the technical basis EPA will use for the next round of PFAS regulatory prioritization.

• Should I worry about PFHpA?

  Context-dependent. If your municipal water utility serves a population in or downstream of a documented fluoropolymer manufacturing area, AFFF training site, or other PFAS contamination zone, PFHpA is likely co-present with PFOA in routine sampling — the same water filtration that addresses PFOA (NSF/ANSI 58 reverse osmosis; certified NSF/ANSI 53 for PFAS) addresses PFHpA. For households outside known contamination zones, PFHpA in drinking water is generally at low concentrations and is one component of total PFAS body burden rather than a standalone concern. The honest framing: PFHpA matters as part of the broader PFAS exposure picture rather than as an isolated single-compound concern.

Related compounds

• PFOA — C8 perfluoroalkyl carboxylate; PFHpA's primary co-contaminant in drinking water and shared-source contamination zones
• PFHxA — C6 perfluoroalkyl carboxylate; structural neighbor (one less perfluorinated carbon)
• PFBA — C4 perfluoroalkyl carboxylate; sibling short-chain PFAS in the alkyl carboxylate spectrum
• PFNA — C9 perfluoroalkyl carboxylate; sibling in EPA 2024 Hazard Index
• PFDA — C10 perfluoroalkyl carboxylate; long-chain sibling at the other end of the spectrum
• PFOS · PFHxS · PFBS · GenX (HFPO-DA) · 6:2 FTS — other PFAS family members

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.