Environmental Occurrence and Biotic Concentrations of Ultrashort-Chain Perfluoroalkyl Acids: Overlooked Global Organofluorine Contaminants

Per- and polyfluoroalkyl substances (PFASs) are a large
group of
anthropogenic fluorinated chemicals. Ultrashort-chain perfluoroalkyl
acids (PFAAs) have recently gained attention due to their prevalence
in the environment and increasing environmental concerns. In this
review, we established a literature database from 1990 to 2024, encompassing
environmental and biological concentrations (>3,500 concentration
records) of five historically overlooked ultrashort-chain PFAAs (perfluoroalkyl
carboxylic and sulfonic acids with less than 4 carbons): trifluoroacetic
acid (TFA), perfluoropropanoic acid (PFPrA), trifluoromethanesulfonic
acid (TFMS), perfluoroethanesulfonate (PFEtS), and perfluoropropanesulfonate
(PFPrS). Our data mining and analysis reveal that (1) ultrashort-chain
PFAAs are globally distributed in various environments including water
bodies, solid matrices, and air, with concentrations usually higher
than those of longer-chain compounds; (2) TFA, the most extensively
studied ultrashort-chain PFAA, shows a consistent upward trend in
concentrations in surface water, rainwater, and air over the past
three decades; and (3) ultrashort-chain PFAAs are present in various
organisms, including plants, wildlife, and human blood, serum, and
urine, with concentrations sometimes similar to those of longer-chain
compounds. The current state of knowledge regarding the sources and
fate of TFA and other ultrashort-chain PFAAs is also reviewed. Amid
the global urgency to regulate PFASs, particularly as countries worldwide
have intensified such efforts, this critical review will inform scientific
research and regulatory policies.