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Unveiling the toxic mechanism of nanoscale tire wear particles to algae: The interplay of particle size, photoaging, and co-existing PFOS.
Summary
Researchers compared nanosized and microsized tire wear particles for algal toxicity, finding that nanosized TWPs caused 23.4% greater growth inhibition at environmentally relevant concentrations due to stronger heteroaggregation with algal cells and greater additive release, while photoaging amplified toxicity in both size classes and co-occurring PFOS played a size- and aging-dependent dual role—reducing nanosized TWP toxicity but exacerbating it after photoaging.
Concerns over the contamination of tire wear particles (TWPs) in freshwater ecosystems are increasing. However, the effects of size, photoaging, and co-exiting pollutants on the environmental fate and toxicity of TWPs are largely unknown. In this study, the algal growth inhibition induced by nanosized TWPs (N-TWPs) was 23.4 % greater than micro-sized TWPs (M-TWPs) at environmentally relevant concentration (1 mg/L). Photoaging significantly enhanced the algal toxicity of N-TWPs and M-TWPs by 5.6 % and 4.6 %, respectively. The presence of PFOS reduced the toxicity of N-TWPs by 24.3 %, while increased the toxicity of photoaged N-TWPs (A-N-TWPs) by 9.3 %. Mechanistically, (1) N-TWPs exhibited stronger heteroaggregation with algal cells and additive release ability as compared with M-TWPs, resulting in greater membrane damage; (2) photoaging enhanced the reactive oxygen species (ROS) generation and additive release by N-TWPs, which subsequently inducing more pronounced algal membrane damage; (3) PFOS showed a size- and aging-dependent dual role in TWPs toxicity. PFOS alleviated the toxicity of N-TWPs through adsorption and metal stabilization, whereas A-N-TWPs combined stronger PFOS adsorption with smaller particle size and enhanced membrane-disrupting ability, facilitating PFOS bioaccumulation and exacerbating algal toxicity. PLS-SEM modeling suggested that metabolic disruption and ROS generation were associated with TWPs-induced algal toxicity. These findings highlight the importance of particulate size, photoaging, and co-existed pollutants when evaluating the environmental risk of TWPs.