Nontarget Discovery of Antimicrobial Transformation Products in Wastewater Based on Molecular Networks

Antimicrobial transformation products (ATPs) in the environment
have raised extensive concerns in recent years due to their potential
health risks. However, only a few ATPs have been investigated, and
most of the transformation pathways of antimicrobials have not been
completely elucidated. In this study, we developed a nontarget screening
strategy based on molecular networks to detect and identify ATPs in
pharmaceutical wastewater. We identified 52 antimicrobials and 49
transformation products (TPs) with a confidence level of three or
above. Thirty of the TPs had not been previously reported in the environment.
We assessed whether TPs could be classified as persistent, mobile,
and toxic (PMT) substances based on recent European criteria for industrial
substances. Owing to poor experimental data, definitive PMT classifications
could not be established for novel ATPs. PMT assessment based on structurally
predictive physicochemical properties revealed that 47 TPs were potential
PMT substances. These results provide evidence that novel ATPs should
be the focus of future research.