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PFTrDA

Perfluorotridecanoic acid

2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-pentacosafluorotridecanoic acid

Also known as PFTrDAPFTriA
Perfluorotridecanoic acidPentacosafluorotridecanoic acid2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-pentacosafluorotridecanoic acidPFTrDAPFTriA perfluorotridecanoic acidPFTrDA perfluorotridecanoic acid276-745-2Perfluorotridecanoic Acid (>85%)

A 13-carbon long-chain PFCA between PFDoA (12C) and PFTA (14C). No PFTrDA-specific RfD; 0.006 ppt benchmark derived from EPA's 2024 IRIS PFDA value. Detected at 41 utilities serving 371K people across 8 states.

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

Primary concern: Immune and developmental effects (PFDA-surrogate)

Affected organ systems

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

Health effects

Carcinogen A substance known or reasonably suspected to cause cancer based on human or animal studies. Immunotoxin Suppresses or alters the immune system. Can increase risk of infection or reduce vaccine effectiveness. Endocrine disruptor Mimics or blocks the body's hormones (estrogen, thyroid, testosterone). Can affect development, reproduction, and metabolism at very low doses. 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. 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

Perfluorotridecanoic acid (PFTrDA, also abbreviated PFTriA) is a 13-carbon perfluoroalkyl carboxylic acid (C13HF25O2, MW 664) — between PFDoA (12C) and PFTA (14C) at the long extreme of the PFCA chain-length spectrum monitored under UCMR 5. The very long perfluorinated chain gives PFTrDA negligible water solubility, extreme bioaccumulation potential, and a multi-year human serum elimination half-life on par with PFDA (~3-5 years) or longer. PFTrDA has been detected at 41 U.S. public water systems serving roughly 371,000 people across 8 states, with Massachusetts dominating the occurrence list (15 utilities, 234K served) and Alabama second (10 utilities).

Pollution sources

Industry Manufacturing Consumer products

Sources

PFTrDA sources mirror those of PFTA and PFDoA: environmental biotransformation of very-long-chain fluorotelomer precursors used in stain-, grease-, and water-resistant coatings on textiles, paper, food packaging, and carpet treatments accounts for most of the diffuse-background detection in the Massachusetts municipal water systems on the occurrence list. Localized industrial point sources include Lincoln, AL (12.5 ppt) and the Gadsden, AL Etowah County metals-finishing district cluster (Gadsden Water Works, Whorton Bend, Highland Water Authority, Northeast Etowah County Co-op all at 2.92 ppt), and Fort Drum, NY (0.008 ppt over 76 tests) is a direct on-base AFFF-related detection. Long-chain PFAS were phased out under EPA's 2010/2015 PFOA Stewardship Program, so contemporary PFTrDA in source water arises primarily from legacy environmental reservoirs and biotransformation of remaining long-chain telomer feedstocks.

Health risks

There is no PFTrDA-specific EPA Reference Dose or IRIS toxicological review. The 0.006 ppt drinking-water benchmark is derived by applying EPA's 2024 IRIS PFDA toxicity value as a surrogate, on the basis of structural similarity and shared toxicological endpoints across long-chain PFCAs: hepatotoxicity, immune suppression, thyroid disruption, and developmental effects. PFTrDA has not been classified as a carcinogen by IARC or NTP. Human pharmacokinetic data is essentially absent; serum half-life is expected to be multi-year. PFTrDA is not included in the 2024 NPDWR Hazard Index mixture and has no individual federal MCL.

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

PFTrDA is among the easiest UCMR 5 PFAS to remove with granular activated carbon: very-long-chain PFCAs adsorb extremely strongly onto GAC and break through later than shorter PFCAs at comparable loading rates. Anion exchange resin and high-pressure membranes (reverse osmosis, nanofiltration) are also highly effective. Conventional treatment processes — coagulation, sand filtration, disinfection, UV, and ozonation — do not remove PFTrDA. 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. As with PFDA, PFDoA, PFUnA, and PFTA, the 0.006 ppt PFDA-surrogate guideline sits below analytical reporting limits and is not operationally verifiable — utilities meeting the long-chain PFAS NPDWR MCLs with GAC, AIX, or RO will incidentally control PFTrDA at the same time.

Gallery

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Related contaminants

Perfluorododecanoic acid (PFDoA) A 12-carbon long-chain perfluorocarboxylic acid, more bioaccumulative than PFDA. Risk-assessed by surrogate to PFDA's 2024 IRIS RfD; detected in 93 U.S. public water systems serving 2.1M people under UCMR 5. Perfluorotetradecanoic acid (PFTA) A 14-carbon long-chain PFCA — the longest PFCA in UCMR 5 (with PFTrDA at 13C). No PFTA-specific RfD; 0.006 ppt benchmark derived from EPA's 2024 IRIS PFDA value. Detected at 64 utilities serving 605K people. 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.