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.

Eurogrip Tyres, the leading tyre manufacturer in India, showcased its premium two-wheeler tyres at the 17th edition of Feria 2 Ruedas (F2R) International Motorcycle exhibition held at Plaza Mayor, Medellin, Colombia. The dates of this high-profile business event in South America's two-wheeler sector are 15–18 May 2025.

For more than 17 years, the Feria de las 2 Ruedas (F2R) has been the leading motorcycle industry event in Latin America. The expo, which takes place every year in Medellín, Colombia, is a vibrant venue for commerce, innovation and growth in the motorcycling sector. Additionally, it gives aficionados the chance to investigate the most recent developments and trends in the industry. The company showcased its premium lineup at exhibit N24 in the Tented Pavillion, which included a range of sport touring, off-road and trail tyres. High-performance versions including the Roadhound, Protorq Extreme, Trailhound STR, Climber, Bee Connect, Terrabite DB+ and Badhshah LX were on display.

P Madhavan, Executive Vice-President – Marketing & Sales, TVS Srichakra Ltd, said, “Eurogrip is focused to deliver innovative products for the global markets. Latin America is a priority market for us, and F2R Expo is a promising platform to engage with our target audience. We are looking forward to interesting business opportunities arising from this expo. Such specialised industry tradeshows add exceptional value to our quest in becoming a leading global tyre brand delivering world class tyre technology.”

Denka Company Limited announced it would record an extraordinary loss of approximately 16.1 billion yen (£85.8 million) as an impairment on manufacturing facilities at its US subsidiary. It will indefinitely suspend chloroprene rubber production at the Louisiana plant.

The Japanese chemical manufacturer, which holds a 70 percent stake in Denka Performance Elastomer LLC (DPE), cited mounting operational challenges, including unexpectedly high costs for pollution control equipment and declining production volumes at the American facility.

“DPE has faced significant cost, production and other challenges at its facility in the United States,” the company said in a statement. “Rising costs are attributable to, among other factors, identification, design, purchase, installation, and operation of pollution control equipment to reduce chloroprene emissions that DPE did not anticipate being required when it acquired the facility from E.I. DuPont de Nemours and Company.”

The subsidiary was established in December 2014 and acquired the chloroprene rubber business from DuPont in November 2015. The Louisiana facility was intended to serve as a second manufacturing site in North America, complementing Denka’s Omi Plant in Itoigawa, Niigata, Japan.

However, according to the company statement, DPE has struggled with multiple operational issues, including “rising energy costs and a shortage of qualified staff necessary to operate new pollution control equipment and implement other emission reduction measures. “

Production volumes have declined partly due to “operational restrictions arising from the pollution reduction measures and unscheduled plant outages associated with supply chain disruptions and severe weather events,” Denka said.

The company noted that these challenges, combined with changes in the global economic environment for chloroprene rubber, have pressured profitability, making near-term improvement difficult.

Denka confirmed that DPE employs 250 people as of December 2024 and will not restart its chloroprene rubber manufacturing facilities following a regular maintenance shutdown. Instead, “all options for the business, including a potential sale of the business or its assets, will be considered,” the statement said.

The company emphasised that “no decision regarding a permanent closure of the facility has been made at this time.”

Customers will continue to be supplied from current inventories and production at the company’s Omi Plant in Japan.

DPE is 70 percent owned by Denka USA LLC, a wholly owned subsidiary of Denka Company Limited, and 30 percent by Diana Elastomers, Inc., a subsidiary of Mitsui & Co., Ltd.

Yokohama Rubber reported a 56.9 percent year-on-year decline in profit attributable to owners for the first quarter of 2025, despite posting a 9.0 percent increase in sales revenue.

The Japanese tyre maker recorded a profit of 8.53 billion yen for the three months ended 31 March, down from 19.8 billion yen in the same period last year. Business profit fell 3.2 percent to 24.07 billion yen, while sales revenue rose to 275.12 billion yen.

The company maintained its full-year forecast, projecting an 11.4 percent increase in sales revenue to 1.22 trillion yen and an 8.8 percent rise in profit to 81.5 billion yen for the fiscal year ending 31 December 2025.

Yokohama Rubber attributed the profit decline to one-time costs related to its February acquisition of Goodyear’s off-the-road (OTR) tyre business, which it purchased for approximately 143 billion yen.

“Profit from existing businesses was strong,” the company said in its earnings statement. “In addition to increased sales volume for the company’s consumer tyres, mainly in overseas markets, and continued expansion of sales of high-value-added ADVAN, GEOLANDAR, and Winter tyres as well as high-inch tyres, profit was boosted by the MB segment’s MIX improvements and structural reforms.”

The tyre segment, which accounts for 91percent of the group’s consolidated sales revenue, saw a 10.4 percent increase in sales to 250.32 billion yen. Original equipment tyre sales were higher year-on-year, driven by “strong sales in Japan of vehicle models equipped with YOKOHAMA tyres and expansion of shipments for Chinese automakers’ new energy vehicles,” the company said.

Replacement tyre sales also increased, supported by higher sales of summer and winter tyres in Japan, increased sales of high-inch tyres in Europe, and stepped-up sales efforts in Asia.

The MB (Multiple Businesses) segment, which represents 8.4 percent of total sales, experienced a 3.2 percent revenue decline to 23.02 billion yen. This was attributed to lower demand from construction machinery makers in Japan and automakers in North America.

The company described an “upbeat” business sentiment in Japan for the quarter, noting that “a steady recovery in inbound demand and increasing orders for construction and logistics projects compensated for weak consumption by domestic households curbing spending in response to rising prices of consumer goods.”

Overseas, the company observed rising inflation concerns weighing on consumer spending in the United States, while in Europe, “manufacturing industries are rebounding and corporate business sentiment is improving.” In China, personal consumption was boosted by the Spring Festival holiday, but high US tariffs “reduced China’s exports and created uncertainty about the future that is weakening industrial activity.”

Swedish speciality chemicals firm Nynas reported solid financial results for 2024, posting an Adjusted EBITDA of 1,333 million Swedish kronor, marginally higher than the 1,316 million kronor recorded in 2023.

The company, which specialises in naphthenic speciality oils and bitumen products, attributed its performance to operational efficiency and commercial success in its niche markets.

“We are delighted with the progress made during 2024, evidencing our right-sized cost base and a more targeted commercial and manufacturing footprint. We have redefined our strategic direction, positioning Nynas as a speciality chemicals company, enabling the energy transition and setting our course for 2035,” Nynas CEO Eric Gosse said in a statement.

The firm highlighted strong cash generation from operations, which it said would support planned investments and longer-term growth initiatives. Nynas also mentioned the ongoing transformation of its Harburg site with plans to monetise the asset eventually.

All three of the company’s production facilities maintained high operational reliability between 95 percent and 99 percent. The Nynäshamn refinery achieved a notable milestone: in May 2024, it set a new monthly production record for naphthenic speciality oils at 42,000 tonnes.

Strategic pivot towards sustainability

Nynas outlined a strategic shift focused on higher-margin speciality materials with sustainable characteristics. The company aims to strengthen its position in European markets through innovation and sustainability initiatives.

“Nynas is uniquely positioned to contribute to the energy transition. Our strategy reflects our purpose to advance a more sustainable society, and our product development pipeline is fully aligned with this goal," Gosse added.

In 2024, the company received an EcoVadis Gold rating, placing it in the top 5 percent of globally rated businesses for sustainability performance.

With consecutive years of strong financial performance, Nynas indicated it continues to monitor debt capital markets to optimise its capital structure “at the appropriate time potentially”.

The Swedish chemicals producer noted that, having ceased operations in the United States in 2022, it remains largely insulated from recent global trade tensions surrounding US import tariffs. The company imports only minimal feedstock from America, shielding it from potential cross-border trade disputes.