Occurrence of Substituted p-Phenylenediamine Antioxidants in Dusts

The substituted p-phenylenediamines (PPDs) represent a suite of effective antioxidants broadly applied in rubber industries. However, knowledge of their environmental occurrences and fate remains extremely limited. Herein, we explored the occurrence of six major PPD antioxidants and one newly defined transformation product in dust particles from different environments, including roads, underground parking lots, vehicles, and houses. The majority of the PPDs exhibited ubiquitous occurrence in these environments. Median concentrations of total PPDs were determined to be 226 ng/g in road dust, 232 ng/g in parking lot dust, and 156 ng/g in vehicle dust, orders of magnitude greater than those in house dust (14.0 ng/g). Different composition profiles of PPDs were also found between house dust and vehicle-related dust, likely indicating the influence of vehicle tires or other rubber products. In addition, a major ozonation product of N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD), 6PPD-qunione, was also identified in dust with levels (median range of 32.2–80.9 ng/g) comparable to that of 6PPD except in house dust. To the best of our knowledge, this is the first systematic investigation of the occurrence of major PPD antioxidants and 6PPD-qunione in various dust matrices. Our findings would attract attention to their environmental fate and ecological and human health risks.