Study on the ecotoxicological effects of airplane tire wear particles versus automobile tire wear particles on earthworms

Adverse effects of tire wear particles (TWPs) as emerging pollutants on soil ecosystems have garnered widespread attention. Current research primarily focuses on automotive TWPs and the toxic effects of airplane TWPs on soil organisms remain unclear. Using earthworms as model organisms, we aimed to compare the toxicities of both TWP types. The results indicated that at the same exposure concentration (3% w/w), neither type significantly inhibited earthworm body weight. However, pronounced differences emerged at the sublethal levels. The aeroplane TWP exposure groups exhibited stronger inhibitory effects on the key antioxidant enzyme indicators. Histopathologically, airplane TWP (particularly in the Three Rings aircraft tire [AT] group) induced severe intestinal damage, including villus disruption, epithelial cell detachment, and sparse longitudinal muscle arrangement. Concurrently, aircraft TWP exhibited stronger suppression of soil and earthworm gut microbial diversity, specifically enriching bacterial genera associated with pollutant degradation and heavy metal tolerance traits. To further trace the origins of toxicity, we combined liquid chromatography-tandem mass spectrometry (LC-MS) with the Toxicological Priority Index (ToxPi) model to assess the risks of the 25 target compounds across six TWP types. N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine (6PPD), 1,2-dihydro-2,2,4-trimethylquinoline (RD), and dicyclohexylamine (DCH) were determined to be the most concerning high-risk compounds, corroborating the strong toxicity observed in TWPs. This study further clarifies the high toxicity of airplane TWPs to soil organisms, providing crucial scientific evidence to refine environmental risk assessment systems for airplane tire-wear particles and to develop targeted control measures.