Search Results (12)

Compared to traditional dense asphalt concrete mixtures, stone mastic asphalt (SMA) generally offers superior performance in terms of its mechanical resistance and extended pavement lifespan. Focusing on the Norwegian scenario, this laboratory-based study investigated the durability of SMA considering the influence of the aggregate shape and petrography. The rock aggregates were classified according to three different-shaped refinement stages involving vertical shaft impact crushing. Further, the aggregates were sourced from three distinct locations (Jelsa, Tau and Dirdal) characterized by different petrographic origins: granodiorite, quartz diorite and granite, respectively. Two mixtures with maximum aggregate sizes of 16 mm (SMA 16) and 11 mm (SMA 11) were designed according to Norwegian standards and investigated in terms of their durability performance. In this regard, two main functional tests were performed for the asphalt mixture, namely resistance against permanent deformation and abrasion by studded tyres, and one for the asphalt mortar, namely water sensitivity. Overall, the best test results were related to the aggregates sourced from Jelsa and Tau, thus highlighting that the geological origin exerts a major impact on SMA’s durability performance. On the other hand, the different aggregate shapes related to the crushing refinement treatments seem to play an effective but secondary role. Full article

Tyre wear particles (TWPs), generated from tyre-road abrasion, are a pervasive and under-regulated environmental pollutant, accounting for a significant share of global microplastic contamination. Recent estimates indicate that 1.3 million metric tons of TWPs are released annually in Europe, dispersing via atmospheric transport, stormwater runoff, and sedimentation to contaminate air, water, and soil. TWPs are composed of synthetic rubber polymers, reinforcing fillers, and chemical additives, including heavy metals such as zinc (Zn) and copper (Cu) and organic compounds like polycyclic aromatic hydrocarbons (PAHs) and N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD). These constituents confer persistence and bioaccumulative potential. While TWP toxicity in aquatic systems is well-documented, its ecological impacts on terrestrial environments, particularly in agricultural soils, remain less understood despite global soil loading rates exceeding 6.1 million metric tons annually. This review synthesizes global research on TWP sources, environmental fate, and ecotoxicological effects, with a focus on soil–plant systems. TWPs have been shown to alter key soil properties, including a 25% reduction in porosity and a 20–35% decrease in organic matter decomposition, disrupt microbial communities (with a 40–60% reduction in nitrogen-fixing bacteria), and induce phytotoxicity through both physical blockage of roots and Zn-induced oxidative stress. Human exposure occurs through inhalation (estimated at 3200 particles per day in urban areas), ingestion, and dermal contact, with epidemiological evidence linking TWPs to increased risks of respiratory, cardiovascular, and developmental disorders. Emerging remediation strategies are critically evaluated across three tiers: (1) source reduction using advanced tyre materials (up to 40% wear reduction in laboratory tests); (2) environmental interception through bioengineered filtration systems (60–80% capture efficiency in pilot trials); and (3) contaminant degradation via novel bioremediation techniques (up to 85% removal in recent studies). Key research gaps remain, including the need for long-term field studies, standardized mitigation protocols, and integrated risk assessments. This review emphasizes the importance of interdisciplinary collaboration in addressing TWP pollution and offers guidance on sustainable solutions to protect ecosystems and public health through science-driven policy recommendations. Full article

Non-exhaust emissions from brakes and tyres are becoming the major transport-related contributor of particulate matter (PM) pollution in cities. Furthermore, tyre microplastics are the major contributor of unintentionally released microplastics in all environmental compartments. The European Union introduced for the first time worldwide limits for brakes (PM₁₀) and tyres (total abrasion mass) with the Euro 7 regulatory step. Thus, the interest in brake and tyre particles regarding health and environmental impacts has significantly increased in recent years. In this review, we summarise studies that assessed the impact of brake and tyre particles on human, mammalian, aquatic, and terrestrial cells and organisms. Furthermore, we summarise the studies that compared the impact of brake and tyre particles to other sources. We also critically examine the sampling methodologies of brake and tyre particles for health and environmental impact studies. Full article

(1) Car tyre microplastic particles (TMPs) significantly contribute to global microplastic pollution, with an estimated annual production of 6 million tonnes. However, the impact of TMPs, particularly tyre and road wear particles (TRWPs), resulting from tyre abrasion on the road on terrestrial organisms, is poorly understood. This study investigated the effects of TMPs and TRWPs on the growth, immune response, behaviour, and cognition of the woodlouse Armadillidium pallasii over 30 days; (2) TMPs and TRWPs were mixed together in the first experiment and provided at different concentrations of 1.25%, 2.5%, 5%, and 10% (w/w), and with soil at 5% and 10% (w/w) concentrations in the second experiment. (3) No differences in survival or immune responses were observed in both experiments. However, isopods exposed to TRWPs showed significant weight gain at lower concentrations but no gain at higher levels. Behavioural tests revealed increased vigilance in TRWP-exposed animals. Micro-FTIR analysis showed that the number of TMPs and TRWPs in the isopods correlated with soil concentrations, and particle size decreased during the experiment. (4) The study highlights the physiological and behavioural effects of TRWPs and the role of detritivorous species in the biofragmentation of TMPs and TRWPs, contributing to the biogeochemical plastic cycle. Full article

Microplastics pollution is becoming a major environmental concern for air, soil, and water. The European Union (EU) Zero Pollution Action Plan targets to reduce microplastics release to the environment by 30% by 2030. Tyre wear is estimated to be the most important contributor to unintentionally released microplastics to the environment. For this reason, the new Euro 7 vehicle emission standard introduced placeholders for limiting tyre abrasion. In this study, we calculate the environmental pollution from tyres using as a basis a recent review on tyre wear emission factors. We also estimate the impact of reducing the average emission factors following the Euro 7 implementation dates. Additionally, we present the cost savings to the EU by such a reduction over a time horizon until 2050. Even though the final cost saving estimations come with some uncertainty due to lack of accurate and up-to-date emission factors, especially for heavy-duty vehicles, the introduction of tyre wear limits has a significant positive impact under all scenarios examined. Full article

The recently introduced Euro 7 emissions standard regulation foresees the addition of abrasion limits for tyres sold in the European Union. The measurement procedures for tyre abrasion are described in the newly introduced Annex 10 of the United Nations (UN) Regulation 117. However, the limits are not yet defined as there is no data available regarding the new procedure. For this reason, a market assessment campaign is ongoing under the auspices of the UN Task Force on Tyre Abrasion (TFTA). Recent reviews on the topic also concluded that there is a lack of studies measuring the abrasion rates of tyres. In this study, we measured the abrasion rate of one tyre model at two different locations (Spain and China) with the aim of deep diving into possible influencing factors. Additionally, wear rates were studied separately for urban, rural, and motorway routes to get more insight into the impact of the route characteristics. The abrasion rates varied from 22 mg/km to 123 mg/km per vehicle, depending on the route (urban, rural, motorway) and ambient temperature. The overall average trip abrasion rates were 75 mg/km and 45 mg/km per vehicle at the two locations, respectively. However, when corrected for the different ambient temperatures, the rates were 63 mg/km and 60 mg/km per vehicle, respectively. The impacts of other parameters, such as driving dynamics and road surface, on the final results are also discussed. The average tread depth reduction was estimated to be 0.8–1.4 mm every 10,000 km. Full article

Background: People living with asthma are disproportionately affected by air pollution, with increased symptoms, medication usage, hospital admissions, and the risk of death. To date, there has been a focus on exhaust emissions, but traffic-related air pollution (TRAP) can also arise from the mechanical abrasion of tyres, brakes, and road surfaces. We therefore created a study with the aim of investigating the acute impacts of non-exhaust emissions (NEEs) on the lung function and airway immune status of asthmatic adults. Methods: A randomised three-condition crossover panel design will expose adults with asthma using a 2.5 h intermittent cycling protocol in a random order at three locations in London, selected to provide the greatest contrast in the NEE components within TRAP. Lung function will be monitored using oscillometry, fractional exhaled nitric oxide, and spirometry (the primary outcome is the forced expiratory volume in one second). Biomarkers of inflammation and airborne metal exposure will be measured in the upper airway using nasal lavage. Symptom responses will be monitored using questionnaires. Sources of exhaust and non-exhaust concentrations will be established using source apportionment via the positive matrix factorisation of high-time resolution chemical measures conducted at the exposure sites. Discussion: Collectively, this study will provide us with valuable information on the health effects of NEE components within ambient PM_2.5 and PM₁₀, whilst establishing a biological mechanism to help contextualise current epidemiological observations. Full article

Tyre particles are generated by shear forces between the tread and the road or by volatilisation. Tyre abrasion (wear) contributes from one-third to half of microplastics unintentionally released into the environment. The major part ends up in the soil, a considerable amount is released into the aquatic environment, and a small percentage becomes airborne. Nevertheless, tyre abrasion contributes to 5–30% of road transport particulate matter (PM) emissions. This corresponds to approximately 5% of total ambient PM emissions. The particle mass size distribution peak at around 20 to 100 μm, with a second peak in the 2–10 μm range. A nucleation mode has been reported in some studies. The absolute abrasion levels depend on the tyre, vehicle, and road characteristics, but also on environmental conditions and driving style. Most tyre particle emission factors in the literature are based on data prior to the year 2000. We aggregated recent studies and found a mean abrasion of 110 mg/km per vehicle or 68 mg/km/t for passenger cars (based on approximately 300 measurements). Based on a limited number of studies, the PM₁₀ emissions were 1.4–2.2 mg/km per tyre. On the other hand, the particle number emissions were in the order of 10¹⁰ #/km per tyre. The ratio of PM₁₀ to total abrasion was found to be 2.5% on average. Finally, the ratio of PM_2.5 to PM₁₀ was calculated to be around 40%. Various mitigation measures for tyre particle pollution could be envisaged; the most direct is the limitation of the tyre abrasion rate, as proposed by the European Commission for the Euro 7 regulation. Other regulatory initiatives are also discussed. Full article

As the number of discarded tyres continues to increase, causing serious environmental problems, the need of recycling the waste tyre rubber become extremely urgent in worldwide. Today, there is an increasing focus on recyclable materials. The reuse of waste tyre rubber in concrete contributes to sustainable development. In the past 10 years, numerous experiments on the recovery of rubber from waste tyres to produce concrete products have been conducted. In this review, we conclude the major achievement of rubberized concrete (RC) durability, discuss and analyse the influence of rubber replacement rates, replacement patterns, particle size and treatment methods. Results show that an increase in rubber content can improve the chloride penetration resistance, acid and sulphate attack resistance, freeze–thaw resistance, and alkali–silica reaction damage resistance of concrete, and the content of 5–20% has a significant improvement effect. Rubber replacing fine aggregate is the best scheme for durability, followed by cement and coarse aggregate. In addition, the recommended rubber particle size is 0–3 mm. However, the rubber particle has adverse effects on abrasion resistance, impermeability, water absorption resistance and carbonation resistance. The pre-treatment of rubber or the addition of supplementary cementitious materials are effective and viable ways of improving the durability of RC. Further research is needed on the long-term durability of RC, as well as on ductility, energy absorption, and thermal and corrosion resistance. Full article

Road markings must be reflectorised with glass beads to be visible to drivers at night, retro-reflecting light from vehicle’s headlights, which is critical for road safety. Four commonly used types of glass beads were evaluated in a laboratory setting for retroreflectivity and their surfaces were analysed using optical and scanning electron microscopy. The glass beads were subjected to abrasion and a visual correlation was sought between the measured retroreflectivity and the surface damage. Scratching the glass bead surface with corundum in a rotary drum resulted in major differences in the rates of damage development, depending on the type of the glass beads, and it could be correlated with the rate of retroreflectivity decay. The relative results from abrasion testing were confirmed under tyre action during a turntable evaluation. Based on the outcomes of these tests, service lives, defined as maintaining appropriately high retroreflectivity, were predicted and used to calculate the consumption of raw materials—the basic sustainability parameter. It was shown that the use of ‘premium’ glass beads, enhanced with TiO₂ and made in a proprietary process, provided the road marking system characterised by the lowest long-term consumption of resources. Full article

As a rubber annular coat of rim wheels, tyres are inevitable parts of all vehicles in modern times. As to their composition, however, they represent a risk for the environment. During the use of tyres, tyre tread patterns become abraded, which results in its gradual wear and necessary re- placement. These micro and nano particles are then gradually extracted into the environment, namely soils and waters. Our research study was focused on the assessment of subchronical phytotoxicity (pot trial with a mixture of substrate and predetermined ratio of abrasion products lasting 28 days) and biological tests (testing phytotoxicity of leaches with predetermined ratio of abrasion products on Petri dishes). The biological tests were comprised two plant species—seeds of white mustard (Sinapis alba L.) and garden cress (Lepidium sativum L.). In the mixtures of substrate with determined shares of abrasion products (5%, 25%, 50% and 75%), respiration of CO₂ was also established by means of soil microbial respiration (Solvita CO₂-Burst). Substrates with 5% and 25% abrasion proportions showed increased biological activity as well as increased CO₂-C emissions. The increasing share of abrasion products resulted in decreasing biological activity and decreasing CO₂-C emissions. The results of subchronical phytotoxicity ranged from 62% to 94% with values below 90% indicating substrate phytotoxicity. The results of biological tests focused on the phytotoxicity of tested samples exhibiting values from 35% to 70% with respect to the germination index with values below 66% indicating the phytotoxicity of tyre abrasion products. Full article

Problems related to non-biodegradable waste coming from vulcanized rubber represent one of the pre-eminent challenges for modern society. End-of-life tyres are an important source of this typology of waste and the increasingly high accumulation in the environment has contributed over the years to enhance land and water pollution. Moreover, the release into the environment of non-degradable micro-plastics and other chemicals as an effect of tyre abrasion is not negligible. Many solutions are currently applied to reuse end-of-life tyres as a raw material resource, such as pyrolysis, thermo-mechanical or chemical de-vulcanisation, and finally crumbing trough different technologies. An interesting approach to reduce the environmental impact of vulcanised rubber wastes is represented by the use of degradable thermoplastic elastomers (TPEs) in tyre compounds. In this thematic review, after a reviewing fossil fuel-based TPEs, an overview of the promising use of degradable TPEs in compound formulation for the tyre industry is presented. Specifically, after describing the properties of degradable elastomers that are favourable for tyres application in comparison to used ones, the real scenario and future perspectives related to the use of degradable polymers for new tyre compounds will be realized. Full article