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.

Smithers, a renowned provider of testing, consulting, information and compliance services, has announced that its proving ground at Treadwell Research Park in Pearsall, Texas, has achieved ISO 17025 accreditation.

Operated on behalf of Discount Tyre, the facility’s accredited scope currently covers wet grip testing and tyre buffing, with plans to expand accreditation to include rolling resistance and pass-by-noise testing. The site boasts diverse paved and off-road test surfaces for comprehensive tyre performance validation. Additionally, it complies with UNECE Regulation No. 117 for Wet Grip and Pass-by Noise standards. This accreditation underscores Smithers' commitment to delivering high-quality testing services in the tyre industry.

Sean Connolly, Director of Test Track Operations at Smithers Winter Test Centre/Pearsall Test Track, said, “The tyre industry is currently focused on a variety of sustainability initiatives, such as reducing the rate of tread wear to extend the life of the tyre. Understanding tyre performance at varying levels of tread wear is critical for tyre manufacturers looking to get the most out of their designs.”

Jim Popio, PhD, Vice President, Smithers Materials Science and Engineering Division, North America, said, “We’re incredibly proud that our existing processes and procedures meet the rigorous requirements of ISO 17025 accreditation. Accurate data, on time, is central of the Smithers promise on a global scale, and we strive to go above and beyond our clients’ expectations with exceptional service as well.”

Michelin, a leading tyre technology company, has launched its first Michelin Experience Store in India, in partnership with Bharat Tyres. The facility spread across 25,000 sqft is located in Adgaon on the Mumbai-Agra highway, Nashik and is Michelin’s largest store in the country.

It is designed not only to provide a premium experience, but also showcases the company’s global legacy through the Michelin Wall. Customers will also be to experience the Heritage Wall that visualise the heritage of both Michelin and its local dealership partner.

The Michelin Experience Store also has a Display Zone that showcases Michelin’s innovations in electric mobility, materials science and environmental responsibility.

The dealership also includes service areas for cars and trucks, PPF coating, precision wheel alignment, advanced balancing services, innovative puncture repair solutions, professional car detailing and a wide array of car accessories. 

Shantanu Deshpande, Managing Director, Michelin India, said, “We are proud to unveil Michelin’s first Experience Centre in India. The sole purpose of this store is to go beyond traditional tyre retail and provide customers an immersive experience of the brand, of our dealer partners and of the technological prowess of our tyre solutions that are safe and sustainable. Nashik, a key hub with growing premium vehicle ownership, is the first of many such centres that will further strengthen our footprint in the western region while providing state-of-the-art experience and services to evolving customers.”

Radar Tyres, the flagship brand of Omni United, has appointed Sami Jauhojärvi, Olympic gold medallist and one of Finland’s most celebrated cross-country skiers, as its official brand ambassador.

Jauhojärvi's sporting excellence – built on resilience, performance and a profound connection with nature – mirrors Radar Tyres' commitment to delivering premium-quality tyres across all seasons and terrains at accessible prices. The brand's comprehensive range includes Summer, All Season, Winter and specialist Ice tyres, designed to meet diverse driving needs with reliable performance.

This collaboration represents a strategic alignment as Radar Tyres expands its European and UK presence. Jauhojärvi will serve as brand ambassador, featuring in marketing campaigns, digital initiatives and local events while sharing his expertise to support Radar Tyres' mission of making high-performance tyres available to all drivers.

G S Sareen, Founder and CEO of Omni United, said, “We’re excited to welcome Sami to the Radar family. Sami’s authenticity, credibility and strong connection with his audience make him an ideal partner for us. He embodies the spirit of perseverance and performance – the same qualities we build into every Radar tyre. As we continue to grow our brand across Europe, partnerships like this play a key role in building deeper connections with consumers. We’re excited to build on this momentum with more such collaborations in the near future.”

Jauhojärvi said, “I am thrilled to represent Radar Tyres, a brand that has a remarkable mission to make premium quality and performance accessible to all and also has deep-rooted values of giving back to society via various initiatives it has undertaken over the years such as supporting breast cancer research. I’m sincerely surprised about the performance and silence of my Radar Tyres and happy to deliver this feedback to all the people.”

Kenda Tires is celebrating Dan ‘The Flying Dutchman’ Vanden Heuvel's nomination to the Off-Road Motorsports Hall of Fame's Class of 2025, recognising his legendary 49-year career as both a champion racer and community leader.

Since entering his first race at age 15 in 1977 at Crandon International Raceway, Vanden Heuvel has become one of off-road racing's most respected figures. His aggressive driving style earned him 20+ Pro-Class wins, five Crandon World Championships and a PRO-2 title. As owner of Flying Dutchman Racing, he mentored numerous drivers including his son Mikey, who secured Kenda Tires' historic first PRO-2 victory.

Beyond competition, Vanden Heuvel's greatest impact comes from his tireless community work. He co-founded the Midwest Off-Road Racing Association, created the Short Course Kart Series for young racers and established the MORR Injured Driver Fund with his wife Nancy. His hands-on approach – from building tracks to mentoring drivers – has shaped generations of off-road enthusiasts.

Now as Kenda Tires' Product Display Manager, Vanden Heuvel continues supporting the sport, assisting drivers across multiple series while representing Kenda at events nationwide. His dedication embodies the brand's values of community and passion for motorsports.

The formal induction ceremony will be held on 2 November 2025 in Las Vegas. This honour celebrates not just Vanden Heuvel's remarkable racing achievements but his enduring legacy as an ambassador who has profoundly influenced off-road culture.

Brandon Stotsenburg, VP of Automotive Division, Kenda Tires USA, said, “Dan is more than a legend – he is a mentor, a servant-leader and the beating heart of the off-road community. He helped deliver Kenda’s first PRO championship and still shows up for others every single weekend. We are honoured to have him represent Kenda and even more proud to call him family.”