For a long time, efforts to reduce traffic-related air pollution have focused mainly on vehicle exhaust emissions. However, as engines become cleaner and electric vehicles grow in popularity, non-exhaust emissions are becoming a dominant source of particulate matter (PM). Road surface wear, tire-road interactions, and the resuspension of accumulated road dust all contribute significantly to airborne PM2.5 and PM10 concentrations.
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Recent research suggests that non-exhaust emissions now represent a major source of road transport particulate pollution, highlighting the need to better understand the role of road surface chemistry in particle formation and release.1 While tire and brake wear have received considerable attention, the chemical composition of pavement materials themselves remains comparatively understudied. Yet the properties of asphalt binders, mineral aggregates, surface treatments, and deposited contaminants directly influence the quantity, size, and chemical characteristics of traffic-generated particles.
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How Road Surfaces Generate Particulate Matter
Particulate matter is generated in several ways. Mechanical abrasion occurs when vehicle tires rub against the road surface, gradually wearing both the tire tread and the pavement. These processes release particles containing a mixture of asphalt fragments, mineral materials, and other materials from the tires and road. As traffic increases, these particles accumulate on road surfaces and can become airborne through traffic or wind-blown resuspension, creating what is known as road dust.2,3
Importantly, particles arising from road surface wear differ from those generated by tires and brakes. Tire wear particles usually contain synthetic rubber, carbon, silica, zinc, and additives, whereas brake wear particles often contain iron, copper, zinc, lead, and other metallic compounds.1 But road surface particles usually come from asphalt and the fragmentation of mineral aggregates.1,4 Although separating these sources in air remains challenging, their combined contribution shows just how important the chemistry of the road surface is in determining overall non-exhaust emissions.
The Influence of Asphalt Composition
Asphalt is a mix of different materials, including binders and mineral aggregates. The chemical behavior of these components influences both pavement durability and particle generation. During aging, asphalt binders undergo oxidation, making them more brittle. This reduces flexibility and makes the pavement more likely to crack and fall apart under traffic.
Research investigating particulate emissions from asphalt wearing courses has shown that different asphalt mixtures release varying concentrations and compositions of particulate matter under abrasion.4 The differences in surface materials affect road wear and tire wear. Concrete is a harder material than asphalt, resulting in a higher abrasion rate and therefore a higher pavement and tire wear emission.3
Environmental Conditions and Surface Chemistry
Road surface chemistry does not operate in isolation. Temperature affects the mechanical properties of asphalt binders, with high temperatures softening pavements while low temperatures increase brittleness and cracking potential. Moisture also plays a dual role. Wet conditions can suppress dust emissions to the surface, yet repeated wetting and drying cycles may damage roads and increase wear.3
Chemical contaminants accumulate on road surfaces from numerous sources, including vehicle fluids, brake pad wear, tire wear residues, de-icing salts, and road wear. These substances can alter road dust chemistry and increase the complexity of emitted particles. Studies of road runoff have identified more than 170 chemicals derived from tire wear, exhaust emissions, and brake pad abrasion.5
Health and Environmental Consequences
The health implications of traffic-generated particulate matter are well established. Fine particles smaller than 100 nanometers can penetrate deep into the respiratory system and cross biological barriers, causing inflammation and oxidative stress.6 Non-exhaust particles may also carry metals such as zinc, which pose significant health risks.6
Beyond human health, these particles contribute to environmental contamination. Road-derived particles accumulate in soils, waterways, and urban sediments. Chemical constituents originating from tires, pavements, and traffic-related residues can impact aquatic ecosystems and alter soil chemistry. Road runoff studies increasingly identify traffic-derived contaminants as an ecological risk.5
Vision For Cleaner Road Infrastructure
Reducing particulate pollution requires a broader approach than simply improving cars. Improved road design represents one promising strategy. More durable asphalt mixtures, high-performance aggregates, and alternative surface materials can reduce wear rates and extend durability. Regular maintenance that prevents road surface deterioration can also minimize emissions of tire and road wear particles.3
Dust suppression methods, including road washing and vacuum-based cleaning systems, may reduce the accumulation and subsequent resuspension of road dust. Researchers are also investigating modified binders, alternative pavement coatings, and sustainable materials designed to improve wear resistance while reducing environmental impacts. As non-exhaust emissions become increasingly important, integrating road engineering with air quality management will be essential.
Conclusion
The chemical composition, physical properties, and interaction of road surfaces with traffic directly influence particulate matter generation. Through pavement wear, tire-road abrasion, and road dust resuspension, roads contribute substantially to airborne PM2.5 and PM10 concentrations.
As cars become cleaner, we must focus on how roads can produce less pollution. Recognizing the role of road surface chemistry offers an opportunity to develop cleaner pavements, improve maintenance practices, and create healthier urban environments.
References and Further Reading
- Costagliola, M. A., et. al. (2024). Non-Exhaust Particulate Emissions from Road Transport Vehicles. Energies, 17(16), 4079. https://doi.org/10.3390/en17164079
- Woo, S.H., et. al. (2024). Correction Method for Resuspended Road Dust Emission Factors according to Vehicle Speed Using a Mobile Monitoring Vehicle. Aerosol Air Qual. Res. 24, 230322. https://doi.org/10.4209/aaqr.230322
- UK Department for Transport. (2025). Road Wear and Dust Resuspension. Department for Transport. Issue 2, T0414 TETI0037
- Fullová, D., et. al. (2017). The Road Surface as a Source of Particulate Matter. IOP Conference Series: Materials Science and Engineering, 236, 012026. https://doi.org/10.1088/1757-899X/236/1/012026
- Poyntz-Wright, I. P., & Tyler, C. R. (2026). Road-Runoff Pollution in English Surface Drains: Chemical Composition and Potential Associated Environmental Risks. Environmental Toxicology and Chemistry, 45(7), 1737-1743. https://doi.org/10.1093/etojnl/vgag105
- Wei, Y., & Kumar, P. (2024). Beyond the Tailpipe: Review of Non-Exhaust Airborne Nanoparticles from Road Vehicles. Eco-Environment & Health, 4(1), 100130. https://doi.org/10.1016/j.eehl.2024.11.003
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