Are tire wear particles toxic
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Toxicity of Tire Wear Particles: An Overview
Introduction to Tire Wear Particles and Their Environmental Impact
Tire wear particles (TWPs) are a significant source of microplastics in the environment, generated from the abrasion of tires during driving. These particles not only contribute to microplastic pollution but also release various chemicals into the environment, raising concerns about their potential toxicity to both aquatic and terrestrial organisms .
Chemical Composition and Toxicity of Tire Wear Particles
Environmentally Persistent Free Radicals (EPFRs) and Photoaging
Research has shown that photoaged TWPs, which are exposed to sunlight, generate environmentally persistent free radicals (EPFRs). These EPFRs significantly increase the toxicity of TWPs by inducing oxidative stress and inflammatory responses in cells. The presence of metals and organic compounds in TWPs further exacerbates their harmful effects.
Leachates from Tire Wear Particles
Leachates, the chemicals released from TWPs into water, have been found to be highly toxic. Studies have demonstrated that both pristine and worn TWPs release harmful compounds such as benzothiazole, 1-indanone, aluminum, and zinc. These chemicals can cause acute and long-term toxicity in aquatic organisms like Hyalella azteca, affecting their growth, reproduction, and survival .
Specific Toxic Compounds
Among the various chemicals leached from TWPs, 6PPD-quinone has been identified as particularly toxic to aquatic life. This compound, along with other tire additives, increases significantly during storm events, leading to elevated concentrations in urban water bodies and prolonged exposure for aquatic organisms .
Ecotoxicological Effects on Aquatic and Marine Life
Freshwater Organisms
TWPs and their leachates have been shown to cause significant harm to freshwater organisms. For instance, exposure to TWP leachates resulted in decreased heart rates, hatching success, and increased deformities in fathead minnow embryos. The presence of benzothiazoles and aryl-amines in the leachates was correlated with these toxic effects.
Marine Sediments and Algae
In marine environments, TWPs accumulate in coastal sediments, altering bacterial community structures and affecting nitrogen metabolism. Aged TWPs, in particular, exhibit higher toxicity due to changes in their surface characteristics. The leachates from TWPs also pose a significant threat to marine macroalgae like Ulva lactuca, primarily due to the release of zinc and other organic components .
Human Health Risks and Environmental Fate
Airborne and Inhalation Risks
While the risk of human health impacts via inhalation of airborne TWPs is considered low, the potential for exposure through the food chain remains unclear. The degradation of TWPs in the environment is slow, with a half-life of up to 16 months in soils, indicating prolonged environmental persistence.
Need for Further Research
Despite the known risks, there is still a lack of comprehensive data on the long-term environmental fate and ecotoxicological impacts of TWPs. More research is needed to develop better analytical methods, conduct long-term monitoring, and understand the degradation processes of TWPs under realistic environmental conditions .
Conclusion
Tire wear particles pose a significant environmental and health risk due to their chemical composition and the toxicity of their leachates. The presence of harmful compounds like EPFRs, benzothiazoles, and 6PPD-quinone highlights the need for improved risk assessment and management strategies. Further research is essential to fully understand the long-term impacts of TWPs and to develop more environmentally friendly tire materials.
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