Toxicity and intergenerational accumulation effect of tire wear particles and their leachate on Brachionus plicatilis.

Tire wear particles (TWP) are one of the main sources of microplastic (MP) pollution in the marine environment, causing adverse effects on marine life and attracting increasing attention. This study aimed to investigate the chemical composition of TWP (particles and leachate) and their toxic effects on Brachionus plicatilis. The results showed that Zn and acenaphthene were the most frequently detected compounds in the three TWP treatments. In the single-generation exposure experiment, TWP leachate showed the highest toxicity potential, followed by nano-TWP (<1 μm) and micro-TWP (1-20 μm). Both nano-TWP and leachate had negative effects on the lifespan and population of rotifers. High-concentration TWP leachate significantly shortened the reproductive period of rotifers, slowed down their swimming speed, and reduced the number of offspring. These negative effects were mainly attributed to the toxic mixture of nano-TWP with additives in the leachate. Furthermore, in multi-generation exposure experiments, the toxicity pattern showed a new trend: the toxicity of nano-TWP exceeded that of the leachate, while micro-TWP continued to maintain the lowest toxicity level. Continuous exposure to TWP exerted a significant negative impact on rotifer lifespan, and this effect increases cumulatively between generations. Notably, TWP was trans-generationally toxic to the lifespan of rotifers, and repeated exposure was more toxic than maternal exposure and continuous exposure. In addition, rotifers can ingest and accumulate TWP, and maternal transfer was another uptake pathway of TWP in rotifer offspring. This finding provided a new perspective for understanding the transmission mechanism of TWP in the marine food chain.