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.

TBC Corporation, a joint venture between Michelin and Sumitomo Corporation, has entered into an agreement to divest its Midas franchise portfolio to Mavis Tire Express Service Corp., which operates a tyre retail chain across the United States.

The deal is expected to be finalised in the first quarter of the fiscal year 2025, subject to the approval of the competent authorities. This deal is a component of TBC's ongoing reorganisation, which intends to concentrate management resources on its core operations.

According to a statement issued by Michelin, “TBC distributes tyres and provides automotive repair and maintenance services in the US, Mexico and Canada. TBC identifies wholesale, distribution and Big O Tires, tyre retail focused franchise portfolio under TBC, as core businesses, leveraging an industry-leading network and scale, whereas Midas activity mostly relies on retail automotive services. The operation will enable TBC to focus on driving accelerated growth and value in its core businesses. It is also an opportunity for Michelin and Mavis to support and reinforce their commercial agreement.”

Pirelli has launched the fifth generation of its iconic P Zero ultra-high-performance (UHP) tyre, the flagship model of the P Zero range.

Thanks to enhanced handling, as demonstrated by track tests on both dry and wet roads, and shorter stopping distances, the P Zero has two main advantages: superior performance and safety. The European wet grip label has given the new tyre an ‘A’ rating since its introduction. In order to improve cornering grip, the contact patch and grooves were updated as part of the development approach, which concentrated on the tread design and tyre structure. To guarantee constant performance over the course of the tyre's life cycle, a more balanced contact patch enhances both braking performance and wear rate. New designs with contrasting marks on the sidewall make the new P Zero visually stand out as well.

With more than 50 models now on the market, the fifth-generation P Zero tyre is available in sizes ranging from 18 to 23 inches. Together with the other P Zero family tyres, these offer comprehensive coverage for the premium and prestige market in all application types. The majority of the new lineup includes Pirelli's specialties, such as Elect, a technology package for electric and plug-in hybrid cars that uses solutions made especially to manage high torque and cut down on noise, increasing range by up to 10 percent because of decreased rolling resistance.

UHP products in the P Zero series are made for a variety of applications, such as track racing, electric vehicles and winter driving. Every driving demand is met by other members of the extended family in addition to this most recent P Zero. These include the P Zero R, which is made to optimise driving pleasure and sporting performance for high-performance cars and SUVs, and the P Zero E, which combines e-mobility and safety (as evidenced by the triple ‘A’ rating on the European tyre label) with a reduced environmental impact (thanks to the use of more than 55 percent natural or recycled materials). Pirelli's P Zero Trofeo RS, which is also approved for road usage, is designed for track driving. The range also includes the P Zero Winter 2 for wet or snowy surfaces.

KraussMaffei Extrusion successfully concluded the KraussMaffei TecDays ‘World of Extrusion’ in Laatzen near Hannover, Germany, with a focus on topics such as pipe & profile, recycling and circular economy.

The three-day event was held from 25 to 27 March and was graced by around 300 visitors from 44 countries. The event provided participants with an ideal platform to exchange ideas on innovations and sustainable solutions in the field of extrusion. Apart from high-profile keynote speeches from industry and research partners and live demonstrations at the state-of-the-art Technology Centre, the event saw the world premiere of the new PVC multi-layer pipe head and a new machine concept for upcycling post-consumer plastic waste.

Extrusion of pipes and profiles was the main topic of the event's first section. Prominent keynote addresses from KraussMaffei Extrusion partners and specialists, including Borealis, Baerlocher, Omya, Plastics Europe and Georg Fischer, offered intriguing perspectives on global extrusion industry difficulties and future trends. The business offered cost-effective and environmentally friendly answers to the urgent problems facing the plastics sector. The ‘Smart Factories’ concept was introduced by Kabelwerk Eupen as a vision of the automated and digitally transformed factory of the future.

A live demonstration of the new PVC multi-layer pipe head, which creates three-layer pipes from virgin material and foamed core, was the focus of the first section. Spider wires and other such weak areas are avoided by the creative distribution method. The new pipe head adds to increased sustainability because of its material versatility, which includes processing recycled materials. Visitors also saw live demonstrations of PVC granulation and PE-PA pipe manufacture.

A novel machine design for the regulated upcycling of post-consumer plastic waste into premium automobile compounds was unveiled during the event's second section, which concentrated on recycling and the circular economy. Accurate, repeatable colours were guaranteed by the groundbreaking ColorAdjust technology. Additionally, a live demonstration of the scalable and energy-efficient manufacture of food-grade rPET granulates was conducted.

The TecDays offered in-depth explanations of several recycling procedures in addition to live demonstrations. The most recent advancements in the circular economy were discussed, along with mechanical, solvent-based and chemical approaches. Prominent research institutes including IKV Aachen and IKK Hannover, as well as industry partners PureCycle Technology, Veolia, Lober, Polymetrix and Exxon Mobil, provided insightful presentations on recent advancements and trends. Innovative technologies including artificial intelligence (AI) in compound production, smart sensors for inline quality monitoring and solutions for cable compounds in an electrified future were included to the programme.

A special event was held in the evening for celebrating 100 years of partnership with Kabelwerk Eupen AG.

Orion S.A., a global speciality chemicals company, has appointed Reciend Group as its distributor of speciality carbon black product lines in Peru. Reciend has been Orion's distributor and agent in Colombia for over 20 years.

Eduardo Belisle, Technical Business Manager, Orion, said, “We know the same dedication and technical work that transformed the Colombian market will be the key factors to drive the evolution for the coatings and plastics market in Peru. We look forward to supporting Reciend on this new journey.”

Highlighting that the collaboration is a strategic milestone that strengthens his company’s mission of bringing specialised solutions to Andean markets, Alejandro Mejía, Chief Strategy Officer of Reciend, said, “It is an excellent opportunity to create even more value for our customers and principals through our talented team, committed to delivering high-performance solutions to industrial markets – such as coatings, plastics, printing systems and battery applications – where we have strong expertise and a broad ingredients portfolio. After decades of working with Orion’s carbon blacks, we’ve established a solid foundation, and now the expansion of our collaboration into Peru enables us to replicate that success in this important and growing market.”