Tire wear, a largely overlooked environmental concern, poses a significant threat to ecosystems and human health. While tires are essential for modern transportation, their continuous shedding of micro- and nanoparticles into the environment demands urgent attention and regulatory action. Current estimates suggest millions of tonnes of tire particles are released annually, contaminating air, soil, and waterways, and contributing significantly to microplastic pollution in the oceans. The complexity of tire composition, coupled with the lack of mandatory disclosure by manufacturers regarding the precise chemical makeup of their products, hinders comprehensive scientific investigation into their environmental and health impacts. This knowledge gap necessitates a reclassification of tire particles as a distinct pollution category, separate from conventional microplastics, to accurately assess and address the specific risks they pose.
The composition of tire particles differs significantly from the more commonly studied microplastics like polyethylene and polypropylene. Tire particles are a complex mixture of synthetic and natural rubber, carbon black, and a range of additives including heavy metals like zinc and lead. This intricate chemical composition, along with a wider particle size distribution compared to other microplastics, contributes to their unique behavior and breakdown in the environment, leading to distinct toxicological challenges. The opacity surrounding the precise chemical makeup of tires, a consequence of the absence of mandatory disclosure regulations for manufacturers, further complicates the study of their environmental impact and potential harm to human health. This lack of transparency underscores the urgent need for stricter regulations demanding full disclosure of tire composition to facilitate comprehensive scientific assessments.
A growing body of research highlights the concerning role of tire wear as a major source of particulate matter pollution, particularly PM10 and PM2.5. These fine particles, easily inhalable due to their small size, contribute to respiratory and cardiovascular problems, including asthma exacerbation and potentially increased risk of premature death. Studies have even indicated that tire wear may be the dominant source of PM10 pollution in some major cities, surpassing the contribution from exhaust gases. This shift in the source of urban air pollution demands a re-evaluation of mitigation strategies, focusing on the control and reduction of tire wear particles.
The chemical additives used in tire manufacturing also present potential environmental and health risks. 6PPD, an antiozonant added to prolong tire life, has been identified as a significant threat to aquatic life, causing mass mortality events in certain fish populations. While the impact of 6PPD on human health remains largely unknown, preliminary studies have detected its presence in human urine samples, raising concerns about potential long-term exposure effects. The continued use of such chemicals, coupled with the lack of comprehensive toxicity data, necessitates further research to understand the potential risks they pose to both humans and ecosystems.
Recognizing the growing concern surrounding tire wear pollution, scientists are calling for urgent action. An international consortium of researchers recently published a review paper urging for the reclassification of tire particles as a unique pollution category, distinct from conventional microplastics. They argue that grouping tire particles with other microplastics underestimates the specific risks they present, hindering effective mitigation strategies. This call to action emphasizes the need for targeted research and regulatory measures to specifically address the environmental and health challenges posed by tire wear. Furthermore, the consortium advocates for greater attention to tire particles in international discussions on plastic pollution, such as the ongoing UN Plastics Treaty negotiations, where the issue has so far received limited attention.
While the international community struggles to reach a consensus on addressing plastic pollution, some progress has been made at the regional level. The UNECE, for instance, has adopted new regulations to measure and limit emissions from braking systems and tire abrasion. This regulation represents a crucial step towards addressing non-exhaust emissions from vehicles and sets a precedent for future regulations targeting tire wear specifically. The European Union’s Euro 7 emission standards, set to take effect in 2026, also aim to reduce particulate emissions from vehicles, including those from tire wear. The effectiveness and potential adoption of these regulations beyond the EU remain to be seen. However, they represent a significant step towards acknowledging and addressing the environmental and health implications of tire wear, paving the way for the development of comprehensive and globally applicable regulations in the future.
