Environmental Occurrence, Influencing Factors, and Toxic Effects of 6PPD-Q

The antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is widely incorporated into tires to extend their service life. However, in the presence of ozone, it is readily transformed into N-(1,3-dimethylbutyl)-N'-phenyl-p-benzoquinone (6PPD-Q). Owing to the large-scale production and widespread utilization of rubber-related products, 6PPD-Q is continuously released into the environment with tire and road wear particles, becoming ubiquitous across multiple environmental compartments. It possesses bioaccumulation potential and exhibits significant toxicity, while multiple exposure pathways enable it to enter human body, posing risks to public health. This review summarizes the environmental distribution of 6PPD-Q in atmospheric, aquatic, and terrestrial systems, and examines key factors influencing its occurrence, including precipitation patterns, traffic characteristics, sunlight, and particle size. The toxicological effects of 6PPD-Q are also discussed. Based on these findings, a comprehensive management framework encompassing "source reduction-process regulation-end-of-pipe treatment" is proposed. Finally, current knowledge gaps are identified and future research directions are highlighted.