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PFDA

Perfluorodecanoic acid

2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-nonadecafluorodecanoic acid

Also known as PFDA
Perfluorodecanoic acidNonadecafluorodecanoic acidPFDANdfdaPerfluoro-N-decanoic acid2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Nonadecafluorodecanoic acidNonadecafluoro-n-decanoic acidPerfluorocapric acid

A 10-carbon long-chain perfluorocarboxylic acid (PFCA) with high environmental persistence and human bioaccumulation. 2024 EPA IRIS RfD for immune/developmental effects yields the strictest UCMR 5 health benchmark.

Group
PFAS
Regulatory status
UCMR
Unregulated Contaminant Monitoring Rule
Top removal tech
Activated carbon

Primary concern: Immune and developmental effects

Affected organ systems

Liver Immune Developmental Endocrine Affecting the body's hormone system — thyroid, adrenal, reproductive, or metabolic hormones.

Health effects

Immunotoxin Suppresses or alters the immune system. Can increase risk of infection or reduce vaccine effectiveness. Developmental toxin Causes harm during development before birth or in early childhood — birth defects, low birth weight, delayed growth, or learning problems later in life. Endocrine disruptor Mimics or blocks the body's hormones (estrogen, thyroid, testosterone). Can affect development, reproduction, and metabolism at very low doses. Hepatotoxin Damages the liver. Effects range from elevated liver enzymes on a blood test to fatty liver disease and, with prolonged exposure, liver cancer.

Exposure routes

Drinking water Dietary Occupational In utero Breast milk

Vulnerable populations

Pregnant Infants Children

Overview

Perfluorodecanoic acid (PFDA) is a 10-carbon perfluoroalkyl carboxylic acid — two carbons longer than PFOA and at the upper end of the long-chain PFCA family. Its long perfluoroalkyl chain gives it low water solubility (about 14 mg/L), strong affinity for protein-rich tissues, and a multi-year human serum elimination half-life: published estimates span roughly 1.6 to 12 years depending on cohort and sex, with most recent peer-reviewed values landing in the 3–5 year range. The combination of extreme environmental persistence and human bioaccumulation drives PFDA's EPA toxicology profile: EPA finalized an Integrated Risk Information System (IRIS) toxicological review of PFDA in 2024, yielding the most conservative drinking-water health benchmark of any UCMR 5 analyte. PFDA has been detected in 265 U.S. public water systems serving roughly 5.8 million people across 19 states.

Pollution sources

Industry Manufacturing Consumer products

Sources

PFDA enters drinking water through the same channels as other long-chain PFCAs: (1) industrial discharges and atmospheric deposition from fluoropolymer and fluorochemical manufacturing — North Carolina dominates the UCMR 5 PFDA detection list (49 utilities, including a tight cluster of Harnett County and Cumberland County systems all measuring 3.90 ppt), reflecting the Chemours Fayetteville Works plume in the Cape Fear River basin that drives much of the regional PFAS contamination story; (2) AFFF firefighting-foam release sites at military installations and civilian airports — Fort Liberty (formerly Fort Bragg) appears in the NC cluster; and (3) environmental biotransformation of long-chain fluorotelomer precursors used in stain- and grease-resistant coatings on textiles, paper, and food packaging. The chronic-source pattern at Pico Rivera, CA (116 of 157 tests positive at 2.46 ppt) and the Gadsden, AL water complex (14 of 42 tests at 1.48 ppt) point to identifiable localized industrial sources outside the dominant NC cluster.

Health risks

EPA's 2024 IRIS toxicological review of PFDA identifies immune suppression — specifically reduced antibody response to childhood vaccines — and developmental effects as the dose-defining endpoints, deriving a chronic Reference Dose that is among the lowest the agency has set for any PFAS. The chronic Reference Dose is so low that virtually any detection of PFDA above the UCMR 5 reporting limit constitutes an exceedance — 251 of the 265 PFDA-detecting utilities exceed it. PFDA has not been formally classified as a carcinogen by IARC or NTP, but the structural similarity to PFOA (IARC Group 1) means cancer screening pressure on PFDA is likely to grow. Reported human serum elimination half-lives vary widely across published cohorts (1.6 years in Worley 2017 vs ~12 years in Olsen 2009 male average) — the wide range reflects real biological and methodological differences and is one reason a single numeric serum half-life is not pinned in this record.

Effective treatments

Activated carbon Granular or block carbon that traps organic contaminants as water flows through. The most common point-of-use filter media — handles chlorine taste, VOCs, pesticides, and many PFAS. Reverse osmosis A semipermeable membrane that pushes water through under pressure, leaving most dissolved contaminants behind. Removes a very broad range — PFAS, lead, arsenic, nitrate, salts — at the cost of slower flow and some wastewater. Ion exchange Resin beads that swap unwanted ions (lead, calcium, certain PFAS, perchlorate) for harmless ones like sodium. Common in water softeners and PFAS treatment columns.

Does not remove

UV Ultraviolet light that disrupts the DNA of bacteria, viruses, and protozoa as water flows past the lamp. Disinfects but doesn't remove chemicals or particles. Chlorination Adds chlorine or hypochlorite to kill bacteria and viruses. The most common disinfection method in US water systems; leaves a residual that keeps water protected through the distribution pipes. Boil Kills bacteria, viruses, and protozoa after a one-minute rolling boil. Does NOT remove chemicals like lead, nitrate, or PFAS — boiling actually concentrates them as water evaporates.

NSF certifications

NSF/ANSI 53 Health-related contaminants NSF/ANSI 58 Reverse osmosis systems

Water treatment

PFDA's long perfluorinated chain makes it one of the easier UCMR 5 PFAS to remove with granular activated carbon: long-chain PFCAs adsorb strongly onto GAC media and resist early breakthrough, comparable to or better than PFOA. Anion exchange resins and high-pressure membranes (reverse osmosis, nanofiltration) are also highly effective. Conventional treatment processes — coagulation, sand filtration, disinfection, UV, and ozonation — do not remove PFDA. Boiling concentrates rather than removes it. NSF/ANSI 53 and NSF P473 certify point-of-use filters for general PFAS reduction; NSF/ANSI 58 covers RO systems. The IRIS-derived health benchmark sits below analytical reporting limits, so no treatment process — including RO at >99 percent rejection — is guaranteed to produce finished water below it; utilities should expect the federal Hazard Index calculation (which excludes PFDA) and the eventual regulatory limit to be the practical compliance target.

Gallery

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Related contaminants

Perfluorononanoic acid (PFNA) A 9-carbon long-chain PFCA with 2024 NPDWR individual MCL of 10 ppt. Same regulatory class as PFOA; principal source is Solvay's South Jersey manufacturing plume. Detected at 894 U.S. utilities serving 26M people across 28 states. Perfluoroundecanoic acid (PFUnA) An 11-carbon long-chain PFCA between PFDA (10C) and PFDoA (12C). No PFUnA-specific RfD; 0.006 ppt benchmark from EPA's 2024 IRIS PFDA value. Detected at 172 utilities serving 4.3M people across 17 states; NJ-dominated occurrence.

Chemistry + classification data sourced from public databases (PubChem, EPA CompTox, IARC monographs); 3D molecular models from 3d.nih.gov where available.