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.

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Dr Suttipong Angthong, Secretary-General of the Association of Natural Rubber Producing Countries (ANRPC), was a distinguished speaker at the World Elastomer Technology and Engineering Forum (WETEF) in Shanghai from 13 to 16 September 2026. Co-organised with RubberTech China, the event attracted over 100,000 professional visitors, industry leaders, scholars and executives from dozens of countries.

His participation delivered strategic benefits for ANRPC and its members by raising natural rubber's profile amid global discussions dominated by synthetic elastomers and advanced materials. Aligning with WETEF's eco-friendly manufacturing focus, he promoted climate-positive practices, traceability and environmentally sound processing methods.

The forum also created direct dialogue channels with major consuming markets and international technical institutions, strengthening trade synergies. It provided valuable insights into breakthrough elastomer science, helping member nations adapt to shifting international market demands.

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Kuraray Co., Ltd. has contributed JPY 9,896,480, roughly USD 64,000, to four international nonprofit organisations. The funds were generated through employee participation in ‘100 Challenge’, a global initiative tied to the company’s centennial observances.

The World Food Programme received JPY 2,804,003, while UNICEF was granted JPY 2,474,120. WaterAid obtained JPY 2,405,394 and WWF was allocated JPY 2,212,963. Each organisation’s share corresponded directly to points accumulated by Kuraray Group staff.

The Group marked its 100th anniversary in June 2026, adopting ‘Possible starts here’ and a related brand story as the guiding concept for its centennial activities. While honouring those who built its first century, Kuraray is pursuing diverse efforts intended to shape the next 100 years, with employees worldwide at the centre. The company seeks to connect staff across departments, countries and languages, fostering unity and connection.

A dedicated app called ‘100 Challenge’, inspired by younger employees, formed one such effort. Participants completed 100 in-app tasks, earning points that supported social contribution activities. The app provided a shared experience regardless of location or role, with individual efforts contributing to both a commemorative mosaic artwork and charitable donations. By combining small individual challenges, the initiative illustrated how personal actions can generate meaningful collective impact, reflecting long-held Kuraray Group values.

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TyreSafe has entered a new partnership with Staffordshire Police, reinforcing a joint commitment to improve road safety and reduce fatalities and serious injuries across the county. The collaboration aims to highlight the critical role tyres play in protecting road users by encouraging simple, regular checks of pressure, tread depth and overall condition.

The value of this preventative approach was recently demonstrated during a multi-agency enforcement operation at the DVSA Vehicle Inspection Site in Doxey. Held on 25 August, Operation Doxey involved Staffordshire Police, West Mercia Police, DVSA, Datatag, the Forensic Collision Investigation Unit and TyreSafe. Inspectors directed 30 vehicles into the site, covering leisure vehicles, towing vehicles, light commercial vehicles and goods vehicles.

Seven tyre and wheel-related defects, mechanical risks and pressure discrepancies were identified. These included a tyre cut through to the cord, which received an immediate prohibition notice, a tyre running roughly 30 percent below recommended pressure, an overweight light commercial vehicle with a nail embedded in a tyre and all four tyres underinflated, a significant rear axle pressure imbalance, a missing wheel nut and an 11-year-old tyre. Leisure vehicle owners generally showed good tread awareness, though pressure maintenance remained an issue, while commercial vehicles presented several preventable defects.

Staffordshire has one of UK’s statistically safest road networks, yet serious collisions remain a concern, particularly on single carriageways. Rural bends, changing speed limits and limited visibility add risk, while motorcyclists and vulnerable road users are disproportionately affected. Common factors include failing to look properly, misjudging speed or path and driving too fast or carelessly. TyreSafe now works with over 260 organisations, and this partnership encourages Staffordshire motorists to make tyre checks routine.

Stuart Lovatt, Chairman, TyreSafe, said, “We are delighted to welcome Staffordshire Police as a TyreSafe partner. While Staffordshire has a strong road safety record, every serious collision has potentially devastating consequences for those involved, their families and their communities. The recent Operation Doxey enforcement activity demonstrates exactly why preventative vehicle maintenance matters. Across just 30 vehicles, inspectors identified a number of serious tyre and wheel defects, including a tyre cut to the cord, significantly incorrect tyre pressures, an embedded nail, a missing wheel nut and a tyre that was 11 years old.

“These findings are a powerful reminder that problems are not always obvious from behind the wheel. Simple checks before a journey can help identify issues before they become a danger on the road. Different roads present different challenges, particularly rural and single carriageway roads where the consequences of losing control or being unable to stop safely can be especially severe. Road safety requires a collective effort, and partnerships such as this are incredibly important. By combining the reach and expertise of Staffordshire Police with TyreSafe’s specialist knowledge and campaigns, we can help more road users understand the simple but crucial role their tyres play in keeping themselves and others safe.”

Police Sergeant Adam Van de Sande, Staffordshire Road Crime – Proactive & Harm Reduction Team, said, “Keeping people safe on Staffordshire’s roads requires everyone to play their part. We are committed to working with partners to reduce the number of people killed and seriously injured on our road network. Operation Doxey demonstrated the value of partnership working, with officers, vehicle examiners and road safety specialists able to identify a range of defects and safety issues before those vehicles continued their journeys.

“Vehicle safety is an important part of that responsibility, and tyres are fundamental to a vehicle’s ability to stop, steer and maintain grip. We are pleased to be working with TyreSafe to raise awareness and encourage motorists to make regular tyre checks part of their routine vehicle maintenance. Our message to road users is simple: don’t wait for something to go wrong. Take a few minutes to check your vehicle and make sure it is ready for the road.”

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The AZuR Network has been honoured with the German Award for Sustainability Projects 2026 in the C2C/Recycling category for its ‘Retreading: Climate Protection on Wheels’ project. The recognition highlights the network's efforts to expand tyre retreading across Germany and Europe, thereby extending the useful life of tyres. Retreading works by reusing a suitable used tyre casing and applying a fresh tread, keeping a substantial share of the original tyre in circulation.

A life cycle assessment commissioned by AZuR and carried out by the Fraunhofer Institute UMSICHT compared retreaded tyres with equivalent new ones. Under the conditions examined, producing a retreaded truck tyre generated roughly 135 kilogrammes less greenhouse gas emissions, a reduction exceeding 60 percent. The process also reuses considerable portions of the existing tyre casing, reinforcing its environmental advantages.

The jury underscored the project's scalability and its relevance to the industry. Official documentation further noted the political integration of the topic as a key strength, with the EU taxonomy confirmation in 2025 representing a tangible milestone. The award places AZuR among well-known companies and innovative projects, including a climate protection cooker initiative in Cameroon, a capsule-free coffee system and a mental health awareness campaign.

Knauf secured first place in the same category with its circular gypsum supply chain, while Schmitz Cargobull led the Mobility and Logistics Solutions category. Other first-place winners included DEKRA, Hansgrohe, Pfleiderer Germany and SBRS. Presented by DISQ with ntv and DUP UNTERNEHMER under Brigitte Zypries' patronage, the 2026 edition saw 433 nominations, with 46 organisations recognised across 19 categories on 17 September in Berlin.

Christina Guth, Network Coordinator, AZuR, said, “This award belongs to our entire network. Retreading only works when many stakeholders collaborate along the value chain – from certified end-of-life tyre recyclers, tyre manufacturers and retreaders to retailers and fleet operators, all the way to academia. The award highlights the potential of using high-quality tyres for longer and keeping their casings in circulation.”

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