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.

Element Fleet Management Corp., the world’s largest publicly traded automotive fleet manager, has nominated Paolo Ferrari and Tracey McVicar to stand for election to its Board of Directors, the Toronto-listed company announced recently.

The nominations, to be voted on at the firm’s Annual General Meeting on 2 May, come as current board members Andrew Clarke and Arielle-Meloul Wechsler have decided not to seek re-election.

Ferrari brings substantial executive experience to the role, having most recently served as Chief Executive Officer of Bridgestone Americas and Bridgestone West, while simultaneously holding the position of Joint Global Chief Operations Officer of Bridgestone Corporation. His prior leadership roles include Chief Executive Officer of Pirelli North America and Latin America, alongside executive positions in telecommunications, technology, and investment banking.

McVicar, a Partner at private equity firm CAI Capital Partners since 2003, previously held senior investment banking positions at Raymond James Ltd. and RBC Capital Markets. Her governance experience includes directorships at Teck Resources Ltd., where she chaired the Audit Committee, and BC Hydro Corporation, where she led the Audit and Finance Committee.

"We are pleased to nominate Paolo Ferrari and Tracey McVicar to our Board," said Element Board Chair Kathleen Taylor. "Paolo and Tracey bring integral skills, perspectives, and experience, and we are confident they will be tremendous assets to the Company. We would also like to thank our outgoing Board members, Andrew Clarke and Arielle Meloul-Wechsler, for their valuable support and contributions to Element."

Hankook Tire’s iON evo electric vehicle (EV) tyre has been voted the test winner with an ‘exemplary’ rating in AutoBild’s 2025 Summer EV Tyre Test.

The testers tested eight tyres in the size 215/55 R 18, all of which were made to be especially appropriate for electric vehicles. The objective for the premium tyre line was to provide unwavering safety while judiciously allocating battery capacity, i.e. to maximise range per battery charge through minimal rolling resistance. The Hankook iON evo, which finished first on the podium with an overall score of 1.1, outperformed all other tyres in the lengthy test.

The Hankook tyre won the top marks in two of the five categories and was the best on the circular track and for handling in the difficult wet surface testing. Also, the high-end tyre made especially for electric cars placed second in the three other categories of braking, aquaplaning and curve aquaplaning. In addition to winning two of the three individual tests, the handling and braking tests, the Hankook tyre dominated the dry surface test. It also placed among the top five drive-by noise comparisons. To further reduce noise levels in the interior, the iON evo is outfitted with Hankook i Sound Absorber technology.

The iON evo performed admirably in both the roll-out and range tests, placing second in the environment category. Lastly, a strong cost rating with continuously high mileage, price per mileage and rolling resistance scores completed the outstanding test result. The final verdict read: “Special EV tyre with good safety reserves during aquaplaning, short braking distances, outstanding driving dynamics, good mileage, good comfort and low rolling resistance.”

Leading tyre-retreading machinery maker Marangoni has unveiled a new strategic sustainability strategy for 2025–2027 that reaffirms its social and environmental pledges.

In order to direct and oversee its ESG (Environmental, Social, Governance) initiatives during the ensuing three years, the tyre retreading expert has voluntarily created a targeted action framework. The framework is in line with the 17 Sustainable Development Goals (SDGs) of the UN's 2030 Agenda. Marangoni claims that the plan was implemented in accordance with globally accepted standards, such as AccountAbility 1000 and the Global Reporting Initiative (GRI) guidelines, and that it is meant to function as a monitoring tool to periodically assess the company's progress as well as a guide for action.

The company has identified 17 specific initiatives as part of this strategy. These were established after a materiality study that took into account input from external stakeholders as well as internal input. Each of the 17 initiatives is built around three core pillars, namely supporting the ecological transition, integrating ESG principles into corporate governance and ensuring a safe, stimulating and inclusive work environment. The result is a ‘balanced approach’ reflecting management’s priorities and stakeholder expectations, said the company.

Trelleborg Group has finalised the purchase of National Gummi AB from the Swedish industrial group National through its Trelleborg Industrial Solutions business unit.

Extruded rubber profiles and gaskets for specialised industrial, automotive and construction applications make up the company offering. Mostly in Northern Europe, sales in 2024 were little over SEK 150 million. The production facility is situated in Halmstad, Sweden. The acquisition is in line with Trelleborg's plan to establish dominant positions in desirable markets. This deal excludes National's activities outside of extruded rubber profiles and gaskets, which will continue to be a part of the National group.

Jean-Paul Mindermann, Business Area President, Trelleborg Industrial Solutions, said, “This is an exciting addition to our portfolio. National has specialist capabilities and knowhow which will allow us to broaden our value-adding offering to customers across Europe.”