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.

Apollo Tyres Ltd has secured a one-season shirt-sleeve sponsorship agreement with AS Monaco, one of French football's most successful clubs, to increase awareness for its premium Vredestein brand.

This partnership will leverage Ligue 1's ranking as the fifth most watched football league in the world to raise awareness of Vredestein's award-winning products among a large audience in France and abroad. On November 22, AS Monaco's home league game against Brest will have the new sleeve branding for the first time. The Vredestein brand will be heavily promoted at Stade Louis-II for the 2024–2025 season, including on player sleeves and LED screens around the field. Exclusive social media initiatives will further help make the brand prominent, reaching a large and interested audience.

Yves Pouliquen, Vice President – Commercial, Europe, Apollo Tyres, said, “This partnership is an exciting opportunity to strengthen Vredestein’s presence in one of our key markets. AS Monaco’s rich history and commitment to excellence mirror our focus on performance and innovation. We look forward to building a successful relationship with the club and celebrating its achievements this season.”

Thibaut Chatelard, Marketing and Revenue Director, AS Monaco, said: “We are delighted to welcome Apollo Tyres and its Vredestein brand to the family of AS Monaco partners. This collaboration makes sense in view of the values we share, such as the constant pursuit of performance and excellence. There’s no doubt that this new support will be precious for the rest of our season, which promises to be thrilling.”

Nexen Tire, a leading global tyre manufacturer, has launched the Nexen N´Blue S tyre, adding to its range of summer tyres and providing drivers with advanced safety, energy efficiency and superior driving stability in wet and dry conditions.

Developed using highly dispersed silica and equipped with an optimised structural design, the Nexen N´Blue S tyre provides reduced road noise and improved driving stability. The tyre features an innovative tread compound, formulated with hydrophilic fillers and microstructure-controlled polymers, and provides lower rolling resistance and exceptional dry and wet grip. The tyre also excelled in test results by demonstrating an 11 percent improvement in wet braking distance compared to its predecessor.

Apart from providing excellent performance, the Nexen  N´Blue S also scores high on the sustainability index. The tyre provides an eco-friendly solution for environmentally conscious drivers by minimising fuel consumption and CO2 emissions. The Nexen N´Blue S summer tyre is available in 58 sizes, which makes it compatible with different types of vehicles.

Kumho Tire Vietnam Co., Ltd. is all set to expand its investment project in Binh Duong province of Vietnam, with the phase 3 of expansion commencing in early 2025. This was discussed at a recent meeting between Vo Van Minh, Deputy Secretary of the Provincial Party Committee and Chairman of the Provincial People's Committee (PPC), and Kim Hyun Ho, General Director of Kumho Tire Vietnam Co., Ltd.

The meeting was held on 13 November at the Administrative Centre of Binh Duong province, as per an official statement. Apart from the company’s investment till date and the planned investment for phase 3, the two also discussed about the challenges and obstacles regarding procedures and processes to have more land funds to expand the manufacturing plant, along with taking measures to tackle the obstacles. Kim Hyun Ho also conveyed to the PPC Chairman that Kumho Tire Vietnam Co., Ltd. belongs to South Korea's Kumho Tire Group and is currently ranked 10th in the car tyre manufacturing industry.

The company had invested in a tyre manufacturing plant in My Phuoc 3 Industrial Park in 2007 with a total initial investment of USD 308 million, which was supplemented by another USD 300 million in 2021. This extended the factory scale to six hectares and increased the production capacity to 12.5 million tyres annually. With the expansion in early 2025, the company will raise its total investment to USD 908 million and increase the factory's production capacity to 17 million tyres annually. The expanded capacity is expected to be operational by early 2026.

Yokohama-ATG, a leading manufacturer of all-terrain and off-the-road tyres, has expanded its Galaxy MFS 101 SDS range of forklift tyres with the launch of white, non-marking tyres.

The Galaxy MFS 101 SDS range consists of puncture-proof SDS tyres with extended wear limits designed for high-intensity working shifts and long durability. These are premium, solid rubber tyres developed for tough demands, a long service life and high driving comfort. The addition of white, non-marking tyres is specifically aimed at clean working environments.

Marked by a 3-stage construction process, the forklift tyres feature reduced heat build-up, effective shock absorption and minimised vibrations. The pattern design guarantees a smooth ride and good steerability thanks to its continuous centre lug and circumferential grooves. Furthermore, the flat walls and wide flat profile offer excellent stability when using a forklift for vertical stacking. The tyres are also equipped with anti-slip steel beads for improved rim fitment

In a case study on a CAT 2.5-tonne forklift that was used for handling heavy pallets on asphalt, the Galaxy MFS 101 SDS outshone the competitors with impressive performance. The tyre delivered an approximate 900 working hours before replacement against competitors’ 500 working hours.