A new study led by an international team of scientists highlights tyre (or 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 behaviour in ecosystems. Researchers are now advocating for the reclassification of TPs as a standalone category of environmental concern.
Henry Obanya, from the Institute of Marine Sciences and member of the Revolution Plastics Institute at the University of Portsmouth, said: "Tyre particles are classified as microplastics, yet they contain hundreds of unknown chemicals, many of which leach into the environment and pose unknown risks. Our study calls for TPs to be separated from traditional microplastics and recognised as a unique threat to environmental and public health. We need focused research to understand their pathways and impact."
Why tyre particles need unique attention
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 stabilising chemicals that make them chemically unique and potentially harmful as they degrade in the environment. While traditional microplastics are typically smaller than 5 mm, tyre 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 study highlights the gap in current knowledge about the environmental presence, transportation, and toxic impact of these particles. The authors have identified ten priority research questions across four key themes: environmental detection, chemical composition, biotic impacts, and regulation.
The research brought together an interdisciplinary network of experts from countries including the UK, US, Norway, Australia, South Korea, Finland, Austria, China, and Canada. Their findings underscore the need for a standardised framework to quantify and manage TPs and their leachates, especially as the global presence of these contaminants rises.
The researchers call for more transparent information on the chemicals used in tyre production, noting that industrial confidentiality currently limits insight into the specific compounds within TPs. 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 tyre additive 6PPD and its transformation product 6PPD-Q has been associated with mass fish die-offs in North America.
Other recommendations include the establishment of an intergovernmental science-policy panel on chemicals, waste, and pollution to tackle TPs on a global scale. By addressing these research priorities, policymakers and regulators could reduce scientific uncertainties and better assess the risks TPs pose to ecosystems and human health. The researchers envision that a clear classification and targeted regulatory framework could lead to sustainable solutions in the tyre and automotive industries, aligning with global Sustainable Development Goals.
Tyre particles are classified as microplastics, yet they contain hundreds of unknown chemicals, many of which leach into the environment and pose unknown risks.
Henry Obanya, Revolution Plastics Institute
"This study is a clear call for coordinated international efforts," said Henry Obanya. "By recognising TPs as a distinct environmental threat, we can drive meaningful research, guide policy, and ultimately work toward a healthier, more sustainable world."
Dr Farhan R. Khan Senior Researcher at Norwegian Research Centre (NORCE) and one of the contributors to the study, said: "By gathering experts that focus on different aspects of TP pollution, from environmental presence, analytical detection, toxic effects and regulation, this study provides an overview of the current state of research and what questions we should be focussed on next. Importantly, this study provides a road-map for future research needs."
Dr. Imari Walker-Franklin, Researcher at RTI International and one of the contributors to the study, said: "This investigation not only presented some of the most urgent questions to address regarding tire particle pollution but also provided actionable steps for researchers, industry and regulators to take."
Meanwhile, Mr Obanya is currently working on a study investigating the effect of chemicals and particles from vehicle tyres on marine life in UK waters.
The project , a collaboration between the University of Portsmouth and the Emissions Analytics Ltd , aims to determine the concentrations of additives in UK aquatic environments, as well as the varying toxicity of car tyre particles from different tyre manufacturers. Scholarship is sponsored by Petroleum Technology Development Fund (PTDF).
