Tire Wear particles (TWP) generated by the abrasion of tire tread against road surfaces, have been shown to represent the majority of anthropogenic particles released into the environment and are considered as an important category of microplastics (MPs). TWP entering the aquatic environment can be ingested by aquatic organisms and produce toxic effects. However, it is not clear whether the particles chemical composition (including polymers and additives) or particles themselves are driving factor for TWP toxicity. To explore this question, we choose Daphnia magna as a test organism and studied the acute toxicity of original TWP particles, leaching TWP particles and leaching solution under different exposure concentrations. The results showed that original and leached TWP particles with an average size of 40um were ingested by Daphnia magna and accumulated in the intestine, which resulted in the inhibition of the activity. Both particles themselves and particles chemical composition produced a negative impact on Daphnia magna physiological activity, such as reduced swimming vigor, inhibited feeding behavior, increased heart rate, decreased thoracic branch activity rate and oxidative stress. However, this toxic effect mainly depended on particle concentration and leaching time. Generally, higher particle concentration and
longer leaching time contribute to higher pollutant concentration in the leaching solution, and the more likely it is to cause toxic effects on Daphnia magna. Interestingly, no significant dose-dependence was observed in our study. Similarly, Toxic effects of raw TWP particles and extracted TWP particles on Daphnia magna appeared more random. Surprisingly, from the activity of acetylcholinesterase (AChE), they did not induce neurotoxicity in Daphnia magna. However, the induction of AChE activity altered diverse behavioral endpoints, which may affect adaptation and survival of the exposed organisms.
 

TWP Extracted TWP Extracted solution Toxicity Water flea