Abstract

In 2021, Science have revealed the cause of “urban runoff mortality syndrome”, i.e., acute and widespread mortality of coho salmon in streams/rivers during rainfall events. N-1, 3-dimethylbutyl-N′-phenyl-p-phenylenediamine quinone (6PPD-Q), an oxidation product of the widely adopted tire rubber additive 6PPD, was identified to induce acute mortality to coho salmon at lower doses (24-h semi-lethal concentration of 95 ng/L). Since then, research interests in the environmental behaviors and toxicities of para-phenylenediamine quinones (PPD-Qs) have greatly arisen. Herein, by applying high resolution mass spectrometry-based suspect screening strategy, we have first identified a series of novel PPD-Qs and revealed their occurrences in the ambient environments of Hong Kong and mainland China. Using synthesized standards, their environmental levels and compositional profiles were specifically characterized, which provided comprehensive data on their multi-route exposures and related human intake doses. Besides that, the environmental characteristics of such emerging contaminants in atmospheric particulate matter (PM2.5) including potential sources, influencing factors, and spatiotemporal variations were investigated with a total of 133 intra- and intercity samples collected over one year. Additionally, health risks regarding the oxidative potential, i.e., ability to induce oxidative stress, of PPD-Qs were evaluated for the first time through an acellular dithiothreitol (DTT) assay. These investigations have provided insights into the occurrences, characteristics, and health risks of emerging PPD-Qs.