Regulated PFAS · EPA MCL in effect
PFNA
Perfluorononanoic acid
A nine-carbon PFAS produced primarily as a byproduct of fluoropolymer manufacturing. Frequently detected alongside PFOA at legacy industrial sites; the New Jersey Drinking Water Quality Institute was the first body to recommend a sub-10 ppt limit on PFNA in 2018.
01Health effects
Linked outcomes
- · Thyroid disruption
- · Immune suppression
- · Liver toxicity
- · Reproductive toxicity
- · Low birth weight
Organs affected
Thyroid, liver, reproductive system
Effects above are summarized from EPA, NIH/NTP, ATSDR, and IARC documentation. Not a clinical or medical claim — see our sourcing standards.
02Where it comes from
Fluoropolymer manufacturing byproduct. Found near plants in NJ, NC, and TX. Less common than PFOA/PFOS but frequently detected together.
03Regulatory status
EPA Maximum Contaminant Level of 10 ppt finalized April 2024. Under reconsideration since May 2025.
04What you can do
If PFNA was detected in your water supply, two filter technologies reliably remove it at the tap:
- RO (reverse osmosis) under-sink systems — 90–99.9% removal across all PFAS chain lengths. Look for NSF/ANSI 58 certification.
- GAC (granular activated carbon) block filters — effective for long-chain PFAS; less reliable for short-chain compounds. Look for NSF/ANSI 53 with NSF P473.
See our certified-filter picks or read the in-depth PFAS removal guide.
Related compounds
Other regulated PFAS
- PFOA →
Perfluorooctanoic acid
The most studied PFAS compound and the namesake of the C8 health crisis. Used for decades in Teflon manufacturing; IARC reclassified it as a Group 1 human carcinogen in 2023.
- PFOS →
Perfluorooctane sulfonic acid
Originally produced by 3M for Scotchgard and AFFF firefighting foam. US production ended in 2002, but PFOS contamination remains widespread at military bases, airports, and downstream of legacy manufacturing sites.
- HFPO-DA →
Hexafluoropropylene oxide dimer acid (GenX)
Marketed as a safer PFOA replacement when introduced in 2009, GenX has become emblematic of the "regrettable substitution" problem — replacing one PFAS with another whose health effects only became clear after widespread environmental release.
- PFHxS →
Perfluorohexane sulfonic acid
Adopted as a shorter-chain alternative to PFOS in fabric protectants and AFFF. Has one of the longest human half-lives of any PFAS — 5 to 8 years — making it slow to clear from the body even after exposure stops.