A new study led by an international team of scientists highlights tire particles (TPs) as the leading contributor to microplastics and calls for urgent, targeted research to address their unique environmental and health risks.
Accounting for nearly one-third of all microplastics, TPs differ significantly from conventional microplastics in size, chemical complexity, and behavior in ecosystems. Researchers are now advocating for the reclassification of TPs as a standalone category of environmental concern.
Unlike conventional microplastics, which are predominantly made of simpler polymer chains, TPs are derived from rubber with a complex mix of synthetic and natural materials. TPs contain numerous additives—such as polyaromatic hydrocarbons, heavy metals, and stabilizing chemicals that make them chemically unique and potentially harmful as they degrade in the environment.
Studies have shown that these chemicals, particularly leachates from TPs, are present in rivers worldwide and have been linked to negative impacts on aquatic life. For example, the tire additive 6PPD and its transformation product 6PPD-Q has been associated with mass fish die-offs in North America.
While traditional microplastics are typically smaller than 5 mm, tire particles (TPs) exhibit a broader particle size distribution, with some particles larger than 5 mm, and are dispersed across ecosystems through road runoff and wind, eventually settling in waterways, soil, and even entering food chains.
The researchers call for more transparent information on the chemicals used in tire production, noting that industrial confidentiality currently limits insight into the specific compounds within TPs.