Tire-Derived 6PPD-Quinone in Water: Environmental Fate, Ecological Risks, and Advances in Its Mitigation.

N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q) has been widely detected in aquatic environments and exhibits extremely high toxicity to aquatic organisms, establishing it as the primary culprit behind urban runoff mortality syndrome. This review systematically examines its environmental migration, transformation pathways, and aquatic distribution, toxicity, and removal. The key findings are (1) 6PPD-Q originates mainly from tire wear and undergoes long-range transport via runoff and atmospheric circulation, with microbial processes dominating its condition-dependent biotransformation. (2) It is widely detected in surface water, groundwater, sediments, and wastewater, showing pronounced spatiotemporal heterogeneity driven by rainfall and snowmelt. (3) 6PPD-Q displays strong species-specific toxicity, particularly to salmonids, causing acute lethality and sublethal effects including oxidative stress, neurotoxicity, and developmental toxicity at environmentally relevant concentrations. (4) Removal technologies include advanced oxidation, adsorption, biodegradation, and coupled approaches. Light-driven oxidation shows promise, yet unrealistic experimental concentrations, unknown byproduct toxicity, and economic feasibility remain key barriers. Based on current findings and identified research gaps, we propose recommendations to deepen the understanding of the environmental implications of 6PPD-Q and guide the development of effective mitigation technologies.