Vehicle-related particulate matter (PM) emissions may arise from both exhaust and non-exhaust mechanisms, such as brake wear, tyre wear, and road pavement abrasion, each of which may be emitted directly and indirectly through resuspension of settled road dust. Several researchers have indicated that the proportion of PM2.5 attributable to vehicle traffic will increasingly come from non-exhaust sources. Currently, very little empirical data is available to characterise tyre and road wear particles (TRWP) in the PM2.5 fraction. As such, this study was undertaken to quantify TRWP in PM2.5 at roadside locations in urban centres including London, Tokyo and Los Angeles, where vehicle traffic is an important contributor to ambient air PM.

The sources of PM2.5 vary spatially with long-range transport sources generated mainly from secondary PM and local sources generated mainly from combustion processes associated with industrial operations and road transport. A recent literature review of various PM2.5 local source apportionment studies conducted in 51 different countries concluded that 25% of urban ambient air pollution from PM2.5 is contributed by traffic, 15% by industrial activities, 20% by domestic fuel burning, 22% from unspecified sources of human origin, and 18% from natural dust and salt. Both primary and secondary PM were accounted for in the analysis and the contribution was dependent on the source. For example, the researchers generally apportioned traffic sources by primary PM emissions and the unspecified sources of human origin based on secondary PM emissions. PM2.5 also varies spatially and temporally.

Over the last 20 years, environmental agencies worldwide have enacted regulations, including those for motor vehicles, in an effort to reduce the emissions of PM2.5; and, indeed, a decline is observable in areas with established monitoring networks. For example, in the US, from 2000 to 2016, the nationwide levels of PM2.5 have decreased 42%; with the vast majority of the measurements below the national standard of 12 μg/m3 since 2012. In Europe (EU-28), the emissions of primary PM2.5 decreased by 16% from 2003–2012.

Vehicle-related PM emissions may arise from both exhaust and non-exhaust mechanisms, such as brake wear, tyre wear, and road pavement abrasion. Several researchers have indicated that the proportion of vehicle traffic attributable to PM2.5 will come increasingly from non-exhaust sources, due to additional regulations limiting vehicle exhaust emissions. The current and future contributions of non-exhaust sources have been evaluated primarily through indirect methods such as various receptor-modelling approaches or air dispersion modelling paired with emission inventories. A recent literature review of non-exhaust emissions reported more than 250 estimates of contribution to ambient air PM.

When tyres interact with the roadway surface, tyre and road wear particles (TRWP) are produced, containing both the tread rubber and embedded road material.

The contribution of tyre wear to ambient PM10 and PM2.5 has been estimated to be between 0.8–8.5% and 1–10% by mass respectively, although the data are sparse and most estimates are indirectly calculated with only a few observational studies. Given the complex composition of the TRWP, a variety of analytical techniques have been proposed, but the only ones with sufficient specificity to the particles are chemical markers associated with the tread rubber, which include monomers styrene and 1,3-butadiene, as well as the dimers vinylcyclohexene and dipentene. Given the predicted increases in non-exhaust emission contributions to PM2.5, the current study was undertaken to measure levels of TRWP in PM2.5 in urban environments where traffic-related PM is significant. Sample locations were chosen to be representative of likely human exposure in various roadside microenvironments. To facilitate comparison to our earlier work and estimates published by others, we present mass-based concentrations and relative contribution to PM2.5 for both TRWP and tread for each sampling location.

Materials, methods

To select the cities for inclusion in this study, data were assembled for large urban areas in Europe, Asia, and the United States. A selection matrix was developed to identify cities based on several criteria including, levels of ambient PM2.5, traffic loads, population density, and local regulatory actions to reduce PM2.5.

In Europe, five cities were considered, including Barcelona, London, Milan, Paris and Rome, with London being ultimately selected. In Japan, six cities were considered, including Nagoya, Osaka, Tokyo, Saitama City, Yokohama, and Kyoto, with Tokyo being ultimately selected. In the US, three cities were considered, including Atlanta, Los Angeles and New York City, with Los Angeles ultimately selected.

Within each city, the site selection criteria included the presence of identifiable traffic and historical presence of high PM2.5 levels where possible. All air samples were collected near the roadside, and the distance from road was dictated by logistical constraints such as security of the equipment and available power sources. For London only, an urban background site was also included.

The analytical technique is based on the characteristic fragments generated by the thermal decomposition of the tyre tread polymers that include styrene butadiene rubber (SBR), butadiene rubber (BR) and natural rubber (NR). Briefly, the method consists of the following steps: the tread rubber polymers in environmental samples undergo thermal decomposition at 670 °C by Curie-point pyrolysis; next, the thermal decomposition products are separated using a gas chromatograph (GC); and finally, the pyrolysis fragments are quantified with mass spectrometry (MS).

The data were evaluated using the Analysis of Variance (ANOVA) and regression models to identify differences among the cities and trends in determinants of TRWP concentrations between sampling locations and cities.

Results

In total 80 samples were analysed, and the TRWP detection frequencies ranged from 0–100%. The lowest detection frequencies were recorded in Los Angeles, with four of the six locations showing no detections. The total ambient PM2.5 levels were low in Los Angeles during sampling days, which was surprising due to the historical levels recorded in the area for the same time of year.

The TRWP made a small contribution to total ambient PM2.5 levels, representing 0.1–0.68% of the total PM2.5 across all locations. The range of concentrations of TRWP were 0.012–0.29 μg/m3 in London, 0.010–0.1 μg/m3 in Tokyo, and 0.004–0.072 μg/m3 in Los Angeles. The highest concentrations were recorded at the Blackwall Tunnel Approach in London (mean 0.104 μg/m3 and range (0.03–0.29 μg/m3)) where significant braking activity occurs before the tunnel portal which creates more tyre wear abrasion than constant speed driving.

The highest TRWP PM2.5 concentration measured in Tokyo was at the Kawasaki Industrial Road location, which had the highest traffic count of the Tokyo sites. In both Tokyo and London, the traffic composition was dominated primarily by passenger car and light duty vehicle traffic, with truck traffic generally comprising less than 20% of the total traffic. One exception was Kawaskai Industrial Road, where the truck traffic accounted for nearly 43% of the traffic.

Uncertainties

The data generated from this research provide an initial observation of TRWP in PM2.5 using methods that are specific to tyre tread, however, they are site specific and may not be applicable more broadly given the small sample size and consequent low statistical power. The calculation of the TRWP concentration involves the assumption of 50% of the polymer in the tread and 50% of tread in the TRWP. However, the 50% assumption of tread in the TRWP is based on the characterisation of bulk TRWP in the size range of 0–150 μm. As such, the composition of the <10 μm fraction has not been specifically characterized.

It is currently unknown if the use of the 50% tread assumption overestimates or underestimates that composition in the <10 μm particles. Previously, the tyre wear contribution to the PM2.5 fraction was evaluated using Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) and the researchers concluded that there was both a pavement and tread component, although the researchers did not have a quantitative estimate of the amounts. More recently, roadside airborne particulate in the 10–80 μm range was characterised using SEM EDX and the researchers concluded that the amount of pavement encrustation of the surface area of the ‘tyre core’ (i.e., tread) ranged from approximately 10% to more than 50%. As such, more research may be needed to refine TRWP composition in the PM10 and PM2.5 fractions.

On 18 June, the prestigious 22nd ‘World Brand Conference and Release Ceremony of China's 500 Most Valuable Brands’ was held in Beijing, organised by the World Brand Lab. Demonstrating its industry leadership, Doublestar achieved an impressive brand valuation of CNY 116.208 billion (approximately USD 16.21 billion), securing the 93rd position overall and maintaining its position as the highest-ranked Chinese tyre brand for yet another year.

This recognition underscores Doublestar's strong market presence and consumer trust, built on decades of innovation and quality craftsmanship. Moving forward, the company has committed to strengthening its brand influence through continuous technological advancement and sustainable development. By focusing on research and production of safer, smarter and more environmentally friendly tyre solutions, Doublestar aims to not only meet evolving market demands but also drive the high-quality growth of China's tyre industry.

Continental Tires has achieved a major sustainability milestone with all its European tyre production facilities now certified under the International Sustainability and Carbon Certification (ISCC) PLUS standard. The certification extends to plants in Lousado (Portugal), Puchov (Slovakia), Korbach (Germany), Sarreguemines (France), Otrokovice (Czech Republic) and Timișoara (Romania), along with the supporting Industria Textil do Ave textile plant in Portugal. The company's Hefei facility in China has also earned this recognition, expanding Continental's sustainable manufacturing network globally.

The ISCC PLUS certification verifies Continental's compliance with rigorous traceability and documentation requirements for renewable and recycled materials used in tyre production. This system enables the company to track sustainable inputs throughout the manufacturing process using the mass balance approach, which allows gradual incorporation of eco-friendly materials while maintaining existing production systems. Continental is currently increasing its use of certified materials, including bio-based synthetic rubbers and circular-process carbon black, as part of its strategy to include over 40 percent sustainable materials in tyres by 2030.

As a globally recognised standard established in 2010, ISCC certification promotes climate-friendly, deforestation-free supply chains across multiple industries. It covers sustainable biomass, recycled materials and renewable resources, providing a framework for transparent, responsible sourcing. For Continental, this achievement represents both a validation of current sustainability efforts and a foundation for future innovations in eco-conscious tyre manufacturing. The company's growing network of certified facilities demonstrates its commitment to reducing environmental impact while maintaining product quality and performance standards across its global operations.

Jorge Almeida, head of Sustainability for Continental Tires, said, “The ISCC PLUS certification of all our European tyre plants is an important milestone and a strong signal for a more sustainable industry in Europe. But we're not stopping there. Our plants in other regions will follow step by step, like our Hefei plant, which is already certified. We have a strong ambition to make our tyre production more sustainable worldwide across our entire supply chain.”

Bandvulc has expanded its Wastemaster 5 tyre range with a new 315/70 size, enhancing options for urban waste collection and recycling vehicles. Originally launched in 2021, this robust tyre boasts a high load rating and is manufactured at ContiLifeCycle’s Ivybridge facility in Devon, which produces Bandvulc and ContiRe retread tyres.

The Wastemaster 5 incorporates ARMORBAND technology, featuring a reinforced rubber layer along the sidewall to resist scrubbing damage and prolong tyre life. Its advanced tread design includes wide zig-zag grooves for mud and water clearance, stone ejection features, stepped blocks and deep sipes for superior traction in tough conditions. This upgrade reinforces Bandvulc’s commitment to durability and performance in demanding waste management operations.

Eurogrip Tyres, India’s top 2 & 3-wheeler tyre brand under TVS Srichakra Ltd, today launched two exclusive retail stores in Chennai – at Selaiyur and Villivakkam. These outlets will stock a full range of two-wheeler tyres, tubes and biking accessories like helmets, alongside offering tyre care, puncture repair, fitment services and engine oil changes.

Catering to scooters, commuter bikes, performance bikes and superbikes, the stores provide diverse tyre patterns and sizes. They will also handle warranty claims for customers. The Selaiyur store is located at J C Group, Plot no 3, Agaram Main Road, Chennai - 600 073, while the Villivakkam outlet is at ST Enterprises, Old no 39E/New no 103, MTH Road, Chennai - 600 049. These expansions reinforce Eurogrip’s commitment to premium service and accessibility.

T K Ravi, COO, Eurogrip Tyres, said, “We are happy to reach out to more customers through our new branded retail stores. In a city that has a bustling two-wheeler vehicle population, there is a need to have more outlets to expand our network. Chennai is an important market for us, and we had opened our first branded retail store in Velachery last May. The response from customers and riders has been encouraging and we are happy to be launching 2 more stores in the city – this will help bolster our brand strength here. We plan to have more such signature stores in different cities to make our products and services easily accessible to customers.”