New Evidence of Rubber-Derived Quinones in Water, Air, and Soil

p-Phenylenediamines (PPDs) have been extensively used in the rubber industry and found to be pervasive in various environmental compartments for decades, while their transformation products and associated ecological and human health risks remain largely unknown. Herein, we developed and implemented a mass spectrometrybased platform combined with self-synthesized standards for the investigation of rubber-derived quinones formed from PPD antioxidants. Our results demonstrated that five quinones are ubiquitously present in urban runoff, roadside soils, and air particles. All of the identified sources are closely related to mankind's activities. Among the identified quinones, N-(1,3-dimethylbutyl)-N '-phenyl-p-phenylenediamine quinone has been recently found to be highly toxic, causing acute mortality of coho salmon in the Pacific Northwest. Ultrahigh-performance liquid chromatography coupled with triple quadrupole mass spectrometry was then applied for quantification of the five quinones and their corresponding PPD antioxidants. The results revealed interesting distinct distribution and concentration patterns of PPD-derived quinones in different environmental matrices. Daily intake rates of these quinones in a compact city of Hong Kong were estimated to be varied from 1.08 ng/(kgmiddotday) for adults to 7.30 ng/(kgmiddotday) for children, which were higher than the exposure levels of their parent compounds. Considering the prevalence of the use of rubber products, the outcome of this study strongly suggests for additional toxicological studies to investigate potential ecological and human health risks of the newly discovered quinones.

Automated summary

The study found that rubber-derived quinones are widely present in urban environments and are closely related to human activities. One of the identified quinones was found to be highly toxic to coho salmon. Mass spectrometry and liquid chromatography-mass spectrometry were used to investigate the distribution and concentration of these compounds. The results showed that the quinones had distinct distribution and concentration patterns in different environments. The estimated daily intake of these compounds by the population in Hong Kong exceeded the exposure levels of their parent compounds. Therefore, further toxicological studies are recommended to explore the potential ecological and human health risks of these newly discovered quinones.