Nontargeted Analysis Reveals Organofluorine Pharmaceutical Compounds Responsible for Formation of Toxic Disinfection Byproducts in a Drinking Water Treatment Plant in China

Toxic
disinfection byproducts (DBPs) formed during chlorination
are a significant concern for drinking water safety. These compounds
were analyzed using nontargeted methods, and their chemical formulas
and structures were determined through tandem mass spectrometry combined
with a novel fragmental chain characterization (FCC) algorithm. This
FCC algorithm significantly improved annotation rates, achieving a
four-fold increase compared to traditional mass spectral matching
strategies. Transformation linkages were identified between precursor
compounds and DBPs, based on their shared fragmental chains. Using
this advanced nontargeted analysis approach, we identified organofluorine
precursors as key contributors to the formation of toxic DBPs in chlorinated
water. These findings were validated using chemical standards, including
fluoroquinolone antibiotics (e.g., enrofloxacin and difloxacin) and
fluorosteroids (e.g., fluocinolone acetonide and triamcinolone). Fluoroquinolone-derived
DBPs were found to be 2.5 times more toxic after chlorination, exceeding
the 1.5 times overall toxicity increase observed in actual water samples.
Fluorosteroids showed smaller toxicity increases (1.3–1.5 times),
but their conversion rates in real water were 1.7–2.3 times
higher than in laboratory conditions. This study highlights the role
of organofluorine precursors in DBP formation and provides an innovative
method to identify unknown DBPs, elucidate their formation pathways,
and trace their sources, advancing water treatment safety.