Ultrashort-Chain PFAS: Emerging Concerns and Analytical Approaches

What are ultrashort PFAS? Ultrashort PFAS are per- and polyfluoroalkyl substances with very short carbon chain lengths of C1 to C3, in contrast to the more commonly analyzed short-chain (C4+) and long-chain PFAS typically measured in methods like EPA 1633A. These compounds include ultrashort versions of several chemical classes: Perfluoroalkyl Carboxylic Acids (PFCAs), Perfluoroalkyl Sulfonic Acids (PFSAs), Per- and Polyfluoroether Carboxylic acids (PFECAs), and Perfluorinated Sulfonylimides (PFSIs). While they represent a relatively new focus in the scientific community, regulatory attention is growing, with two ultrashorts—bis(trifluoromethylsulfonyl)amine (TFSI) and Perfluoropropanoic acid (PFPrA)—already added to EPA's Regional Screening Limits (RSLs).

Why could ultrashort PFAS be important?

• Mobility – Ultrashort PFAS are highly mobile due to their small size and high water solubility, allowing them to travel rapidly through groundwater and potentially reach drinking water systems more quickly than longer-chain compounds.
• Persistence – Like other PFAS, ultrashorts contain strong carbon-fluorine bonds that resist degradation. These ultrashorts could persist in the environment for decades or longer.
• Removal – Conventional water treatment technologies that work reasonably well for longer-chain PFAS may be less effective at removing ultrashort-chain PFAS, making them particularly difficult to remediate once in the environment.
• Destruction – some destruction technologies may inadvertently create ultrashort PFAS as intermediate byproducts during the destruction of longer chain PFAS, requiring careful validation and monitoring of transformation products.
• Bioaccumulation – Recent biomonitoring studies have detected TFA and PFPrA in human serum, with TFA found at median concentrations of 6.0 ng/mL—higher than legacy PFAS like PFOA. However, significant knowledge gaps remain regarding their bioaccumulation potential, long-term ecological impacts, and health effects.
• Unknowns – Significant data gaps exist regarding ultrashort PFAS toxicity, bioavailability, and health effects. Despite widespread environmental occurrence and confirmed human exposure, comprehensive dose-response data and health risk assessments remain largely unavailable, with EPA's recent health toxicity values based on limited studies.

How do we analyze for ultrashort PFAS? While there is currently no published regulatory method for ultrashort PFAS, the analytical technologies used in existing methods, like EPA 533, 537.1, 1633A, and ASTM D-8421 can be used. The downside is that the solid phase extraction (SPE) methods, as written in these methods, are insufficient to extract many of these ultrashorts from aqueous samples. A co-solvation / direct aqueous injection method was developed for aqueous samples along with a solvent extraction method for solid samples. These methods can be used for potable water, groundwater, surface water, wastewater, leachate, soil, sediment, and biosolid matrices.

Airdate: Tuesday, February 3, 2026 - 1:30 PM ET

Length: 60 minutes 

Presenter: Jonathan Thorn - Eurofins Environment Testing