EPA legal limit
No federal limit
Maximum Contaminant Level
EWG health guideline
1 ppt
Science-based, stricter target
Health effects
PFHpA has been shown to affect thyroid hormone levels, liver function, and immune response in animal studies. Its inclusion in the EPA Hazard Index rule reflects agency concern about its combined effects with other PFAS at low concentrations. Research on its individual health effects at drinking water concentrations is ongoing.
Where it comes from
Industrial use as a processing aid in fluoropolymer manufacturing and as a replacement for longer-chain PFAS. Found alongside PFOA, PFOS, and other PFAS in contaminated groundwater near industrial sites, military installations, and in water impacted by PFAS-containing biosolids.
How it's regulated
No individual EPA MCL. Part of EPA's Hazard Index (HI) mixture rule under the 2024 PFAS NPDWR. Note: EPA proposed in May 2025 to rescind the Hazard Index portion of the rule, which would remove PFHpA from federal regulation. Monitored under UCMR5. EWG health guideline: 1 ppt.
How to filter pfhpa
Not all filters address pfhpa. Look for independently certified filters—NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is pfhpa?
PFHpA is a seven-carbon carboxylic acid PFAS detected in water serving 63 million people across 41 states in UCMR5 monitoring. It bridges short-chain and long-chain PFAS in both structure and toxicological properties. PFHpA is one of four PFAS included in EPA's Hazard Index mixture rule alongside PFHxS, PFNA, and HFPO-DA.
What are the health effects of pfhpa?
PFHpA has been shown to affect thyroid hormone levels, liver function, and immune response in animal studies. Its inclusion in the EPA Hazard Index rule reflects agency concern about its combined effects with other PFAS at low concentrations. Research on its individual health effects at drinking water concentrations is ongoing.
Is pfhpa regulated in drinking water?
No individual EPA MCL. Part of EPA's Hazard Index (HI) mixture rule under the 2024 PFAS NPDWR. Note: EPA proposed in May 2025 to rescind the Hazard Index portion of the rule, which would remove PFHpA from federal regulation. Monitored under UCMR5. EWG health guideline: 1 ppt.
Where does pfhpa come from?
Industrial use as a processing aid in fluoropolymer manufacturing and as a replacement for longer-chain PFAS. Found alongside PFOA, PFOS, and other PFAS in contaminated groundwater near industrial sites, military installations, and in water impacted by PFAS-containing biosolids.
How do I remove pfhpa from tap water?
The most effective methods for removing pfhpa are: Reverse osmosis (RO), NSF 58 certified RO system, Activated carbon block filter. Look for NSF-certified systems—independent certification confirms removal claims have been verified.
Is pfhpa in your water?
Enter your ZIP code to see the measured level in your specific utility.