Environmental Occurrence, Source Identification, and Health Hazards of Ultrashort-Chain PFAS in the Yangtze River Delta

Ultrashort-chain per- and polyfluoroalkyl substances
(USC-PFAS),
defined by three or fewer carbon atoms in their backbone, represent
an emerging class of environmental contaminants whose prevalence and
hazards remain inadequately characterized. This study conducted a
comprehensive survey of seven USC-PFAS and 37 other PFAS compounds
in aquatic environments within the Integrated Demonstration Zone of
the Yangtze River Delta, a region undergoing continued industrialization.
Results showed that USC-PFAS overwhelmingly dominated PFAS profiles,
with trifluoroacetic acid (TFA) representing the most abundant species.
Mean concentrations of TFA reached 8.7 × 104 ng/L
in surface water, 8.0 × 104 ng/L in source water,
and 6.9 × 104 ng/L in tap water, constituting 90.1%
to 99.6% of total ∑44PFAS across matrices. When
TFA was excluded, the remaining ∑6USC-PFAS contributed
44.0% to 58.8% of the total PFAS burden. Trifluoromethanesulfonic
acid (TFMS) was the second most abundant in surface and source waters,
while trifluoromethane sulfonimide (Ntf2) ranked second in tap water.
Source apportionment analyses implicated battery electrolyte formulations
as major contributors of TFMS and Ntf2. Hazard prioritization based
on persistence, mobility, bioaccumulation, and toxicity (PMBT) metrics,
alongside measured environmental levels, identified TFA, TFMS, perfluoro-2-(perfluoromethoxy)propanoic
acid (PMPA), and perfluorooctanoic acid (PFOA) as high-hazard compounds.
These findings suggest that USC-PFAS constitute a pervasive and underregulated
class of pollutants, whose high mobility and recalcitrance challenge
current assumptions regarding their environmental safety and call
for urgent regulatory reevaluation.