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.

Zeon Corporation has secured a Bronze rating in the sustainability assessment conducted by EcoVadis SAS, a gobally recognised sustainability rating agency based in France.

EcoVadis SAS uses four criteria – environment, labour and human rights, ethics and sustainable procurement – to assess the sustainability performance of more than 150,000 businesses and organisations in 185 countries. Zeon Group received the Bronze rating, which is granted to the top 35 percent of assessed businesses and organizations, in recognition of their efforts.

With the aim of attaining sustainable growth alongside society and in accordance with the company’s corporate philosophy of ‘Contributing to the preservation of the Earth and the prosperity of the human race’, Zeon has been advocating for sustainability management. The company reaffirmed its continuous support to tackle environmental and social challenges while striving to live up to societal expectations.

Hoosier Racing Tire, a subsidiary of Continental AG specialising in the production of racing tyres, has expanded its range of 13-inch radial slick tyres with new sizes and compounds designed specifically for F4, F3 and Radical race cars.

The MS compound combines exceptional performance with unmatched reliability. In terms of operating range, longevity and repeatability across several heat cycles, the compound's special formula has been race-proven in numerous formula car spec tyre series and is regarded as the industry standard by many open wheel racers.

Starting in 2025, the North and Central American (NACAM) Formula 4 Championship series will use the new Hoosier MS tyres, which come in sizes 200/540R13 and 250/575R13. As the exclusive tyre for the Hoosier Formula Cup Championships in the Ultimate Cup European Series, the Hoosier MS tyres in the 240/580R13 and 300/590R13 are starting their second season.

Nokian Tyres has started delivering tyres from its new factory in Oradea, Romania. Winter and all-season tyres are the first to be delivered to clients and consumers in Central Europe via Nokian Tyres distribution centres.

Strategically located close to Central and South European consumers and customers, the factory will focus on passenger car tyres for these markets. The groundbreaking ceremony was held in May 2023 and the first tyre was manufactured in July 2024. The plant uses the most up-to-date technology to manufacture tyres and is the first full-scale, carbon-free tyre factory in the world. All of its energy is produced without the use of fossil fuels. The factory has already received three prestigious awards, namely the 2025 Award for Environmental Achievement of the Year – Industry Contribution at the Tyre Technology International Awards for Innovation and Excellence, Business Review’s Award for The Most Impactful Investment of the Year 2025 in Romania and the Sustainable Manufacturing Award 2025 in Romania – Industry Tomorrow.

The first passenger car tyre line made at the Romanian facility, the Nokian Tyres Seasonproof 2, was just introduced by the firm. By the fall of 2025, customers in Central and South Europe will be able to purchase the all-season tyre line in sizes suitable for contemporary passenger cars, SUVs, and CUVs. In addition to offering outstanding performance and a comfortable driving experience in the summer, the tyre offers outstanding grip on snow and slush. Up to 38 percent of the materials used in Nokian Tyres Seasonproof 2 are recycled, renewable, and ISCC PLUS certified. It is the first tyre produced commercially by the firm that has such a large percentage of recycled and renewable materials. The firm plans to provide additional Romanian-made products for drivers throughout Central and South Europe in the upcoming months and years.

Along with plants in Dayton, US, and Nokia, Finland, the Romanian plant is the company's third production facility. To draw in competent workers, the company is actively recruiting in Romania, particularly in Bihor County. The factory currently employs around 300 workers and expects the workforce to be over 500 when the factory is at full capacity.

Paolo Pompei, President and CEO, Nokian Tyres, said, “This week marks the start of the tyre deliveries from our factory in Oradea, Romania. The first truck loaded with Oradea made tyres left from the factory taking the tyres to our distribution centres and later to our customer and consumers in Central and South Europe. The factory, which is the world’s first full-scale zero CO2 emission tyre factory, will strengthen our ability to serve our consumers and customers in Central and South Europe and beyond and support our growth. Reaching this milestone in less than two years from the Groundbreaking of the factory is a significant achievement for us and I am very proud of the Nokian Tyres team who has worked hard to make this possible. I also want to thank all partners and Romanian officials who have helped us along the way.”

Linglong Tire, one of the world's leading tyre manufacturers, will make its debut with a stand at Autopromotec in Bologna, Italy, from 21 to 24 May 2025. The company will exhibit its main brand, Linglong, together with the two Group brands, Crosswind and Leao Tire, which are also sold in Europe, in Hall 20 (booth no. C 68).

The company will display the most significant Linglong passenger vehicle profiles, including the Sport Master and the Linglong Sport Master e, which has been tuned for NEVs. Along with new original equipment tyres that Linglong will provide straight to the OEM manufacturing line, the stand's main attraction will be the new Linglong van tyre Dura Master Van e, which will mark its global debut in Bologna. Also on display will be the primary Linglong truck tyres, all of which are produced in the recently constructed European tyre factory in Serbia, together with a variety of special tyres (OTR). The most significant car and truck tyres from the Leao Tire brand will also be on display, along with the newest Crosswind brand profiles, which are made solely in Europe.