Tire-derived antioxidants in terrestrial ecosystems: Occurrence, mechanistic toxicity, and sustainable mitigation...

Annual global emissions of tire-derived antioxidants, including N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), rise due to increasing tire production. Its primary transformation product, 6PPD-quinone (6PPD-Q), persists in terrestrial ecosystems and poses substantial ecological risks. This review synthesizes current knowledge regarding the occurrence, environmental transport, detection methods, and mechanistic impacts of 6PPD and 6PPD-Q in the terrestrial environment. These compounds are frequently detected in urban runoff, reclaimed wastewater, dust, and soils. Exposure to these contaminants inhibits plant growth, induces oxidative damage, and promotes conjugative transfer of plasmid-mediated antibiotic resistance genes within rhizosphere microbial communities. Advanced analytical and molecular techniques have provided mechanistic insights into their environmental persistence and toxicity mechanisms. Engineered biochar-based approaches, particularly those incorporating pyroligneous acid, show promise for contaminant sequestration, mitigation of oxidative stress, and suppression of antibiotic resistance gene dissemination through synergistic adsorption and redox-modulating mechanisms. A comprehensive understanding of the occurrence, transport, and biological interactions of these compounds is critical for predicting ecological impacts, identifying vulnerable soil-plant systems, and developing effective remediation strategies. This review highlights critical knowledge gap and outline framework for sustainable management of tire-derived antioxidants in terrestrial ecosystems.