Air pollution remains a persistent global issue, with particulate matter (PM) pollution posing significant health and environmental challenges, particularly in urban areas. As exhaust emissions decrease, non-exhaust emissions (NEEs) – particles from brake, tire, and road wear – are now a dominant source of urban particulate matter (PM). NEEs contribute to poor air quality and water and soil contamination through microplastic pollution, raising concerns for the ecosystem and public health. However, regulation is hampered by data gaps around emission factors, chemical composition, and health impacts of NEEs.
NEEs are responsible for 78% of PM10 and 65% of PM2.5 emissions from road transport in Barcelona. Like London, PM10 emissions are dominated by brake wear in passenger cars. However, for heavy trucks, exhaust emissions are the primary contributor among all sources (brake, tire, road wear, and exhaust). For lighter trucks, PM2.5 is almost equally distributed among the different sources.
A recent report by e:misia, in partnership with EIT Urban Mobility, Transport for London (TfL), and the Greater London Authority (GLA), focuses on NEEs in London and explores their sources, impacts, and mitigation strategies. Among the NEEs, brake wear is the dominant source in urban settings, accounting for significant airborne particle emissions. The report finds that through regenerative braking, electric vehicles (EVs) can reduce brake wear by over 80%, thus substantially improving air quality. Additionally, EVs eliminate tailpipe emissions, offering clear benefits.
Tyre wear is the second-largest source of NEEs. Although only 1–5% of tire particles become airborne, the remainder accumulates in road dust and enters water systems. This issue is exacerbated in urban environments and warmer climates. Heavier vehicles, including EVs, which are, on average, 20% heavier than conventional internal combustion engine (ICE) vehicles, increase tire wear—raising long-term concerns. Road wear, the third component, is difficult to isolate but adds to PM levels, particularly where road maintenance is poor.
Despite increased tire and road wear, the overall impact of fleet electrification remains positive due to the elimination of exhaust emissions and significant reductions in brake wear. The forthcoming Euro 7 regulation, taking effect in late 2026, will impose limits on brake wear emissions, with tire wear limits to follow in 2028. These regulatory steps represent a significant move toward NEE mitigation, though their benefits will accrue gradually as they only apply to new vehicles. Caution is advised regarding using new materials in brakes and tires, as some low-wear components may introduce other environmental or health risks.
The report recommends a multi-level policy response. At the local level, cities should integrate NEEs into air quality strategies, expand Low-Emission Zones (LEZs), and promote public transport and active mobility options. Crucially, a modal shift—reducing reliance on private vehicles—can yield up to five times the impact of electrification alone in cutting NEEs. Driving behavior also matters: smoother driving, lower speeds, and optimized traffic flow can reduce wear-related emissions.
At the national level, early adoption of low-wear components and public awareness campaigns should complement fleet electrification. Internationally, harmonized monitoring standards, toxicity assessments, and coordinated research are needed to address existing knowledge gaps.
In summary, while fleet electrification and regulations like Euro 7 are vital, they are insufficient. The most impactful strategy is reducing vehicle kilometers through modal shifts. A comprehensive mix of regulation, urban planning, behavioral change, and technology adoption is essential to effectively mitigate NEEs, protect public health, and ensure long-term air quality and environmental sustainability.
Source: EIT Urban Mobility