Exploring the Occurrence and Temporal Variation of ToxCast Chemicals in Fine Particulate Matter Using Suspect Screening Strategy

Existence of emerging contaminants in the environment is of great importance for health risk assessment. The consensus on categories and numbers of the emerging contaminants in airborne fine particulate matter (PM_2.5) is still extremely deficient. In this study, an in-house data set was constructed containing 890 unique ToxCast (Phase I and Phase II) chemicals. Occurrence and temporal variation of the chemicals was investigated by a suspect screening workflow in 60 PM_2.5 samples from January to December of 2016 in Beijing. Eighty-nine compounds were identified in 12 substance categories, which covered a broad range of physicochemical properties. Quantification/semiquantification results showed that phthalates, phenols, and carboxylic esters were the three most predominant categories, with mean concentrations of 7.82, 4.42, and 4.11 ng/m³, respectively. Four diverse temporal variation patterns were discerned, which could be explained by correlations of chemical concentrations (or instrumental responses) with meteorological parameters. An extended retrospective suspect screening was also performed to reveal the presence of several analogues of the identified chemicals that were not included in the data set. Another 75 pollutants were tentatively recognized, and comparison of estimated composition profiles based on instrumental responses suggested the identified ToxCast chemicals are a notable subset of typical emerging contaminants. The results might facilitate ranking of organic pollutants with active biological effects in PM_2.5 samples.