Environmental factors ultraviolet a and ozone exacerbate the repeated inhalation toxicity of 6PPD in mice via accelerating the aging reaction

The burden of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its oxidized products on human health can no longer be ignored due to the detection types and concentrations in the environment continue to increase. Environmental ozone (O₃) and ultraviolet A (UVA) may induce ozonation and photoaging of 6PPD to produce toxic products. However, the impact of specific environmental conditions on the aging and toxic effects of 6PPD is unclear. This study investigated the aging effects of O₃ and UVA on 6PPD, and compared the repeated inhalation toxicity of differently aging 6PPDs in C57BL/6 male mice. The result showed that UVA and O₃ accelerated 6PPD aging, and the aging products varied depending on the O₃ and irradiation conditions. After 10 weeks of inhalation intoxication at human comparable level, mice exhibited significant neurobehavior alterations, respiratory dysfunction, and DNA damage in the blood, showing significant heterogeneity among groups. Notably, 6PPD treated with perozonation and UVA aging may be the most toxic. The study suggests inhalation health risks of transportation derived tire pollutants under the influence of ground-level ozone and ultraviolet light need more attention, and provides new insights into risk assessment and pollution control of 6PPD and other pollutants from the perspective of environmental factors.