Environmental fate, toxicity, and mitigation of 6PPD and 6PPD-Quinone: Current understanding and future directions

N'-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a widely used antioxidant in the rubber industry, has garnered global attention due to the high toxicity and ecological-health risks posed by its environmental oxidation product, 6PPD-quinone (6PPD-Q). With the continuous release of tire wear particles (TWPs), 6PPD-Q is ubiquitously distributed in atmospheric, aquatic, and terrestrial environments, as well as within organisms, where it bioaccumulates through food chains. Notably, 6PPD-Q has been detected in human urine, serum, and cerebrospinal fluid, and its association with abnormal α-synuclein aggregation in the brains of Parkinson's patients further underscores its neurotoxic risks. This review systematically examines the environmental occurrence and migration patterns of 6PPD and 6PPD-Q, their multisystem toxicity, highly sensitive detection technologies, and pollution control strategies, while highlighting critical gaps in current research, such as chronic exposure mechanisms, combined pollution effects, and environmental safety thresholds. By synthesizing existing knowledge, this review provides a scientific foundation for elucidating the ecological and health risks of 6PPD-Q, offering critical insights to advance environmental regulatory policies, promote green transformation in the rubber industry, and safeguard global ecological security. Future research should prioritize long-term toxicity studies, refined detection techniques, and sustainable regulatory frameworks to mitigate the ecological and health risks posed by these emerging contaminants.