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Electric Vehicles and Air Pollution
Tyre particles: How EVs are a climate solution with pollution problem
Context: A new study published in Soft Matter, a journal of the Royal Society of Chemistry, by researchers from the Tata Institute of Fundamental Research (TIFR), IIT Bombay, and Columbia University, reveals that EVs release significantly more plastic particles from tyre wear than conventional vehicles. This is due to their increased weight and unique driving dynamics, which accelerate the degradation of tyres and release of harmful airborne microplastics.
EVs: A Solution with a Hidden Cost
- Electric vehicles (EVs) are widely hailed as a critical solution to combat climate change, primarily due to their potential to eliminate greenhouse gas (GHG) emissions from road transport.
- However, while addressing the global challenge of climate change, EVs may be inadvertently contributing to a different environmental problem—air pollution.
Understanding Tyre Degradation and Pollution
- Tyres disintegrate over time due to wear and tear, releasing small rubber particles into the air—a largely overlooked source of pollution. These particles are broadly classified into two size ranges:
- Small particles: Between 1 to 10 micrometres, which can remain suspended in the air.
- Larger particles: Over 100 micrometres, which tend to settle on the ground due to gravity.
- The study, titled “Mechanism of Microplastic and Nanoplastic Emission from Tire Wear” (Shankar Ghosh et al.), establishes a clear relationship between vehicle weight, speed, and the size and quantity of tyre particles released.
- Heavier and faster-moving vehicles, like EVs, tend to produce more smaller particles—the ones most likely to pollute the air and pose health risks.
- Importantly, the study also distinguishes between two different degradation processes:
- Primary fragmentation, caused by sudden braking or impact (like potholes), releases mostly small particles.
- Sequential fragmentation, resulting from gradual wear, leads to larger particles.
- This distinction implies that while improving road conditions may reduce larger particles, it would do little to curb the emission of smaller, more dangerous particles.
Why Are EVs More Problematic in This Context?
- EVs are, by design, significantly heavier than their internal combustion engine (ICE) counterparts due to the massive batteries they carry—typically weighing between 300 to 900 kilograms.
- This added weight necessitates stronger vehicle frames and results in an overall 15–20% increase in weight over similar petrol vehicles.
- Additionally, EVs can accelerate faster, generating more friction and heat on the tyres. This combination of heavier loads and faster acceleration increases the incidence of primary fragmentation, resulting in a higher release of fine plastic particles into the atmosphere.
- These emissions are not from tailpipes but from non-exhaust sources, which currently fall outside the scope of many air quality regulations, most of which focus on PM2.5 and PM10 particles.
Global Context and Adoption Trends
- The findings of this study are globally significant. Road transport contributes nearly 10% of global GHG emissions, mostly from burning fossil fuels.
- EVs currently make up only 2% of the global vehicle fleet, yet they represented around 20% of new vehicle sales globally in the previous year.
- In India, only 2.5% of vehicles sold in 2024 were electric, but the government aims to raise this to 30% by 2030.
- In China, nearly half of all car sales in 2024 were EVs.
- As EV adoption accelerates worldwide, the implications of tyre-based microplastic emissions grow in parallel.
What Needs to Be Done?
- The study’s authors argue that urgent policy responses and technological interventions are needed to address this emerging challenge. Key recommendations include:
- Updating air quality regulations to account for particles smaller than PM2.5, especially microplastic emissions from tyres.
- Encouraging tyre manufacturers to develop stronger, more durable tyres that can withstand the stress of heavier EVs without excessive degradation.
- Expanding emissions standards to include non-exhaust emissions, such as those from tyre wear.
- Exploring technological solutions, like capturing tyre particles at the point of release to prevent their dispersion into the environment.
This study highlights a critical but overlooked downside of EV deployment and calls for holistic strategies that ensure air pollution is not exacerbated while pursuing climate goals.
About EVs
- An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. Unlike conventional vehicles, which rely solely on fossil fuels, EVs use electric motors that run on gasoline or batteries.
- Battery Electric Vehicle (BEV): BEVs operate solely on electricity, drawing energy from the on-board battery. They don’t have petrol or diesel engines and don’t use tailpipe emissions. Compared to other types of EVs, BEVs offer longer electric driving capabilities.
- Hybrid Electric Vehicle (HEV): HEVs combine an internal combustion engine (usually gasoline) with a battery-powered electric motor. The engine can drive directly or charge the battery when needed. HEVs are not as efficient as fully electric vehicles or plug-in hybrids.
- Plug-in Hybrid Electric Vehicle (PHEV): PHEVs use both an internal combustion engine and an external (via plug) charger. They offer more performance than HEVs but less than BEVs.
- Fuel Cell Electric Vehicles (FCEV): FCEVs generate electricity from chemical energy, similar to hydrogen fuel cells. They do not emit tailpipe emissions and are considered zero-emission vehicles.
