Tire Wear Pollution: Rising Concern for Air Quality

Summary

When we talk about car pollution, exhaust fumes usually steal the spotlight, but tire wear is a hidden threat we can’t ignore. Every drive releases tiny tire particles filled with rubber, chemicals, and road dust into the air, soil, and water. These tire wear particles (TWPs) aren’t just microplastic pollutants; they can harm our lungs, disrupt aquatic life, and contribute to long-term environmental damage. Factors like incorrect tire pressure, poor alignment, and rough roads make the problem worse.

TWPs spread through air and water, eventually settling in oceans, rivers, and soil. Tackling this issue needs smarter tire designs, smoother road surfaces, better filtration systems, and stronger regulations. Collaboration across automakers, researchers, and policymakers is critical, and networks like the Indian Air Quality Network (IAQN) are already building momentum. As we move toward cleaner transportation, let’s not overlook what’s happening beneath our wheels, because even the smallest particles can create a lasting impact.

Tire Wear Pollution: Rising Concern for Air Quality

When we talk about “car pollution,” what’s the first thing that comes to mind? For most people, it’s exhaust fumes. But there’s a hidden source we rarely think about, tire wear.

Every drive leaves behind more than just mileage. As tires roll over roads and highways, they shed tiny particles into the air, invisible yet harmful. Unlike visible smog or noisy engines, tire wear pollution often goes unnoticed. But it’s a major contributor to microplastic pollution and air quality degradation, impacting both our ecosystems and our health.

Here’s the reality: Tire wear particles (TWPs), smaller than 5mm, form due to the constant friction between tires and road surfaces. They mix synthetic and natural rubber, heavy metals, chemical additives, and road debris. Research shows that TWPs make up 5–10% of global microplastic pollution, with over 6 million tons released into the environment every year.

And the dangers go beyond just pollution. TWPs can trigger oxidative stress in our lungs, disrupt eye development in aquatic life like zebrafish, and even cause pulmonary fibrosis in mammals. Plus, manufacturing tires itself isn’t clean; it demands huge amounts of fossil fuels and contributes to deforestation.

As we move toward greener transport solutions, it’s time to also rethink what’s happening under our wheels, because even the smallest particles can leave a big impact.

What Are Tire Wear Particles (TWPs)?

Particles with a diameter of 5 mm or less, known as tyre wear particles (TWPs), are primarily created by mechanical shearing force or volatilisation in the presence of physical friction between the tire and the road surface. Typical components of TWPs include tread and road-based materials that incorporate chemical additives and rubber polymer. The latest research shows that tyre emissions constitute around 5-10% of the overall worldwide main sources of microplastics and that yearly TWPs produced by tyre wear can exceed 6.1 million tons. Tyre wear particles (TWPs) contain natural and synthetic rubber, carbon black, plasticisers, antioxidants, sulphur, heavy metals, and other additives. Artificial rubber and natural rubber are the primary components of TWPs.

The toxicity mechanism of TWPs constitutes a prominent area of academic research. According to a literature review, it was found that TWPs have three main toxic mechanisms: oxidative stress, developmental toxicity, and other adverse effects. TWPs can induce oxidative stress in biological cells, thereby triggering host lung cell apoptosis and causing respiratory system depression. At the same time, TWP leachates can inhibit zebrafish eye photoreception by reducing thyroid hormone secretion and cell proliferation, thereby inhibiting eye development. TWPs may additionally inhibit miRNA expression in lung tissue by controlling the cytoskeletal rearrangement function. This stops the production of functional actin in lung tissue and causes pulmonary fibrosis in mice. The diverse ecotoxicological effects and associated toxicity mechanisms of tyre wear products (TWPs) demonstrate that they present significant environmental hazards, while tyre production entails substantial ecological consequences, including ongoing deforestation and the detrimental use of fossil fuels in the synthesis of synthetic rubbers and the manufacturing process. Contemporary automobile tyres necessitate approximately 7 gallons of oil for production, whereas truck tyres demand 22 gallons. Therefore, it is necessary to establish effective source-process-end control measures to mitigate the environmental risks of TWPs.

Factors that accelerate Tire wear

Underinflated tyres

If the air pressure in the tyres is insufficient for an extended period while driving, both shoulders of the tyre will deteriorate. The reason for this is that the tyre surface is not subjected to consistent pressure. Increased rolling resistance, overheating, and irregular wear patterns are the result of the excess strain that the sidewalls of the tyre endure. Therefore, it is imperative that you maintain the appropriate tyre pressure.

Overinflated tyres

Conversely, tyres can maintain excessive pressure for an extended period while on the road. Excessive inflation leads to quicker wear on the central tread, which affects the overall balance of the tyre. This leads to diminished grip, a rougher driving experience, and inconsistent tyre wear. Once more, the straightforward answer: ensure that your tyres are properly inflated to the recommended pressure.

Incorrect wheel position

When a wheel is misaligned, it can lead to uneven tread wear because the tyre is not following its intended path. Nonetheless, improper wheel alignment can also lead to uneven tyre wear, a condition that can be easily detected by touch. Adjusting our approach is the key to addressing this issue. Ensuring proper wheel alignment promotes an even weight distribution across the tyres, which in turn extends their lifespan.

Incorrect tyre size for the vehicle

Along with a misaligned wheel position, there’s also a chance that your vehicle may have the wrong tyre size. Make sure your tyre size is appropriate for your vehicle to avoid early damage. To prevent any possible issues, ensure that you verify the appropriate tyre size and check that the wheel is properly aligned.

Bead damage

The purpose of the tyre bead is to ensure that the tyre and wheel are properly connected, without air escaping. As soon as there is even the slightest damage to the bead, it should be replaced immediately for safety. Damaged or corroded tyre beads compromise the seal between the tyre and the wheel, leading to air leaks, uneven wear, and potential safety hazards. The cause of bead damage is often that the mounting head is not properly adjusted or the bead is not properly pressed into the rim bed.

Bad shock absorbers

When there is a large imbalance in the wheel and if there is a gap in the suspension rubbers or steering knuckles, this can cause damage to the shock absorbers. But also, when the tyre lugs are strongly deformed, the shock absorbers can no longer do their job properly. Worn-out or malfunctioning shock absorbers can amplify tyre wear. They fail to dampen road impacts effectively, causing the tyres to bounce excessively and wear unevenly.

Sidewall wear

Sharp edges are the enemies of sidewalls. Damage caused by sharp edges is easy to recognise. In principle, this wear is not dangerous. Another cause of sidewall wear is run-up. Here, check that the tyre is not too large for the vehicle and that the wheel is in the right position. Wear can also come from dying out from the sunlight. If these cracks come down to the carcass threads, then new tyres are needed.

Cutting tooth wear due to poor road conditions or driving conditions

Aggressive driving or traversing harsh terrains can cause cutting tooth wear, leading to premature tyre damage and decreased traction. Cutting tooth wear can occur on non-driven axles. Low tyre pressure and tracking are the cause of this particular type of wear and can be seen around the entire contour of the tyre and often across the entire width of the tread. Regularly inspect your tyres for signs of damage and consider adjusting your driving style based on road conditions. In some cases, it’s best to consider changing the wheel position regularly to counteract tooth wear.

Distribution characteristics of tyre wear particles in environmental media

Tyre wear particles (TWPs), primarily produced through urban road traffic, are widely distributed across various environmental media via two major pathways: air transport and runoff transport. As vehicles move, TWPs are emitted and settle mostly near roadsides due to gravity and wind, with the highest concentrations found in soil sediments within five meters of the road. Smaller particles tend to become airborne and disperse with the wind, while larger particles settle on roads and are carried into soil, surface water, and groundwater by rainwater runoff.

Micro- and nano-sized TWPs can migrate under the influence of rain, wind, and ocean currents, dispersing into the atmosphere, rivers, soil, or even the ocean. It is estimated that 67% of TWPs enter soil, 12% enter air, and 12% enter surface water, with about 50% eventually reaching the ocean. Some TWPs also accumulate in wastewater treatment plants.

The freshwater environment plays a significant role in the migration of TWPs. Rain and surface runoff carry TWPs into surface waters such as rivers and lakes. The concentration of TWPs in surface runoff is about ten times higher than in the receiving water bodies. Studies show that microplastic levels in stormwater treatment wetlands are higher at outlets than at inlets, indicating enrichment during treatment. These particles, mostly black fragments (75%), are largely attributed to tyre wear. Sediment samples show 15–38% of microplastics are synthetic rubber carbon-filled particles likely originating from tyres, as identified by FTIR.

TWPs also enter the soil environment through rainwater runoff or sewage sludge application following wastewater treatment. A study using Zn as a tracer showed a significant decrease in TWP content with soil depth even after 80 years of roadside accumulation. Soil acts as a physical filter, preventing deeper penetration and contamination of groundwater. The concentration of TWPs declines with increasing distance from the road.

In the atmosphere, although most TWPs are not suspended, vehicular motion can resuspend them. Airborne concentrations decrease with distance from the road, with only a small fraction migrating through the air. Using scanning electron microscopy (SEM), Kunze et al. (2022) categorised TWPS into PM1, PM2.5, PM4, and PM10. Fine particles (∼10 μm) can travel over 14-meter-high obstacles, while larger ones (10–100 μm) settle more locally in areas of low airflow. Particle size inversely affects their atmospheric residence time and transport range.

Environmental distribution and migration of TWPs are influenced by both external factors such as airflow, water flow velocity, pH, and ionic strength, and intrinsic particle properties like size, density, and surface characteristics. Due to their persistence and widespread distribution, TWPs present ecological risks. Prolonged exposure may harm organisms at multiple biological levels. Thus, it is essential to study their environmental behaviour and risks comprehensively.

Mitigation Strategies and Solutions

A) Technical Mitigation Approaches

1. Tire Design Improvements

• Develop tyres with more wear-resistant compounds

• Utilise advanced rubber formulations that reduce particle generation

• Implement innovative tread designs that minimise abrasion

• Create tyres with longer lifespans to reduce overall particle production

2. Road Surface Engineering

• Design smoother road surfaces with reduced abrasiveness

• Use advanced road materials that minimise particle generation

• Develop polymer-modified road surfaces that reduce wear

• Implement precision road surface finishing techniques

3. Filtration and Capture Technologies

• Install roadside biofilters and vegetation barriers

• Develop specialised drainage systems with particle capture mechanisms

• Create microporous road surface layers that trap wear particles

• Implement roadside collection systems near high-traffic areas

4. Vehicle Technology Interventions

• Develop active tyre wear monitoring systems

• Implement tyre pressure management technologies

• Create vehicle suspension systems that reduce road surface impact

• Design wheel alignment technologies to minimise uneven tire wear

5. Regulatory and Policy Measures

• Establish maximum wear rate standards for tyres

• Implement mandatory tyre particle emission testing

• Create incentives for low-wear tire technologies

• Develop comprehensive tracking and reporting mechanisms for tire wear

6. Environmental Capture Strategies

• Develop specialised urban drainage systems

• Create wetland and green infrastructure to intercept and filter particles

• Implement constructed bioswales along roadways

• Design sediment traps in stormwater management systems

7. Material Innovation

• Research alternative tyre materials with lower wear characteristics

• Develop biodegradable tire compounds

• Create synthetic rubber alternatives with enhanced durability

• Explore nanotechnology solutions for reducing particle generation

B) Emerging Technologies

• Develop advanced sensors for real-time particle tracking

• Create machine learning models to predict and minimise wear

• Explore biomimetic approaches to reduce friction and wear

• Investigate quantum material design for next-generation tyres

C) Collaborative Approach

• Effective mitigation requires collaboration between:

• Automotive manufacturers

• Tyre producers

• Road infrastructure engineers

• Environmental scientists

• Policymakers

• Transportation authorities

Conclusion

Tire wear is a silent yet significant contributor to air pollution and microplastic contamination. While it escapes the attention given to tailpipe emissions, its environmental and health impacts are undeniable. From urban air loaded with particulate matter to aquatic ecosystems polluted with synthetic rubber, the footprint of tyre wear spans across terrestrial, aquatic, and atmospheric domains. Its toxicological effects, ranging from respiratory diseases to developmental disruptions in aquatic species—demand urgent attention.

Tire wear particles (TWPs) are not just an engineering problem but an environmental crisis in the making. Addressing it requires a multifaceted and collaborative response. From redesigning tyres and road surfaces to developing advanced filtration systems and enforcing regulatory standards, a blend of innovation, policy, and awareness is essential. Emerging technologies like real-time sensors and machine learning models further pave the way for smarter, data-driven solutions. At the same time, public education and sustainable transportation practices must also evolve to reflect this often-overlooked source of pollution.

To make meaningful progress, it's crucial to bring together a broad coalition of industry leaders, researchers, environmental advocates, and regulatory bodies. Collaborative platforms like the Indian Air Quality Network (IAQN) provide an excellent opportunity for synergy. IAQN fosters global partnerships among environmental scientists, air quality experts, policymakers, and technology innovators. Through such networks, best practices can be shared, cutting-edge research can be translated into action, and a global response to tyre wear pollution can be coordinated effectively.

As we steer toward a more sustainable mobility future, let’s not overlook what we’re leaving behind: tiny particles with a huge impact.

FAQs

Q1. What are tire wear particles (TWPs)?

A. Tire wear particles (TWPs) are tiny fragments, usually less than 5mm in size, that are released when tires rub against road surfaces. They are made of synthetic and natural rubber, chemical additives, and road dust.

Q2. How do tire wear particles impact the environment?

A. TWPs contribute significantly to microplastic pollution, contaminate soil and water bodies, and degrade air quality, posing a threat to ecosystems and human health.

Q3. Are tire emissions worse than exhaust emissions?

A. While exhaust emissions have stricter regulations, tire emissions remain largely unregulated. Research shows that TWPs can be just as harmful, especially due to their role in microplastic and particulate pollution.

Q4. Can tire wear pollution affect human health?

A. Yes, inhaling fine tire particles can lead to respiratory problems, oxidative stress, and even long-term lung damage.

Q5. How can we reduce tire wear pollution?

A. Solutions include using eco-friendly tires, maintaining proper tire pressure, supporting sustainable transportation methods, and pushing for stronger environmental regulations.