Comparative toxicological impacts of tire wear and latex particle leachates on zebrafish embryos: Chemical characterization, oxidative stress, and transcriptomic disruption

Rubber-derived pollutants, such as tire wear particles (TWP) and latex particles (LAP), pose increasing threats to aquatic ecosystems due to their complex chemical composition and potential toxicity. This study systematically evaluated the embryotoxicity of 30-day leachates from TWP and LAP (10 g/L) in zebrafish (Danio rerio) by integrating chemical characterization and toxicological assessment. ICP-MS and GC–MS analyses revealed elevated levels of toxic metals, notably zinc and aluminum that exceeded established ambient water quality criteria for aquatic life, along with numerous organic contaminants including antioxidants, plasticizers, and accelerators. LAP leachates exhibited significantly greater toxicity than TWP, as indicated by a lower LC₅₀ (3.33 g/L), increased mortality and malformation rates, delayed percent hatched, and reductions in spontaneous movement, heartbeat, and body length. Oxidative stress biomarkers revealed disrupted antioxidant enzyme activity and elevated malondialdehyde (MDA) levels, particularly in the LAP group. Transcriptomic profiling revealed that both ferroptosis and arachidonic acid metabolism were commonly enriched pathways. Notably, LAP exposure induced broader alterations in metabolic and inflammatory processes, whereas TWP exposure primarily impacted stress and apoptosis-related pathways. RT-qPCR validation confirmed significant gene expression changes, including the downregulation of cardiac-related genes (tnnt2d, stc1l) and upregulation of oxidative stress and inflammation markers (ptgs2b, mt2). Collectively, these findings demonstrate the heightened embryotoxicity of LAP leachates and the divergent molecular responses elicited by TWP and LAP, underscoring the need for targeted environmental regulation and risk mitigation strategies.