Heavier battery cars are causing greater wear and more tyre particle pollution than from car exhausts, suggesting the urgent need for stronger regulation.
Particle pollution produced by tyre wear is found to be 1,850 times higher than emissions from the tailpipes of modern cars, according to the latest testing.
Research done by UK-based independent testing company Emissions Analytics showed that used tyres produce 36 milligrams of particles each kilometre, which is nearly 2,000 times higher than the 0.02 mg/km average from exhausts.
In testing more than 250 different types of tyres, usually made from synthetic rubber, a material that is derived from crude oil, it found that particles from tyre wear contain a wide range of toxic organic compounds, including known carcinogens. They then go straight into soil and water, polluting the sources. Car exhaust emissions, on the other hand, remain in the air for a period of time and affect air quality.
The study’s results also suggest that around 11% of the mass of tire emissions is smaller than 2.5 microns in diameter, the standard unit for fine particle dust (Particulate Matter 2.5) in the atmosphere. This means that the small sizes make them easier to enter the body through inhalation and organs via the bloodstream.
Every year, at least one in 10 people around the world suffer from premature deaths from air pollution-related diseases. Many developed countries have regulated particle emissions from tailpipes to ensure clean air quality. In California for example, the state has imposed stringent state standards (more so than federal) that limits how much pollution and greenhouse gas vehicles can emit. Design advancements such as better filters mean that pollution from car exhaust has significantly lowered. Across Europe, tailpipe emissions from cars are now far below the legal limit.
“Tyres are rapidly eclipsing the tailpipe as a major source of emissions from vehicles,” said Nick Molden from Emissions Analytics. “Tailpipes are now so clean for pollutants that, if you were starting out afresh, you wouldn’t even bother regulating them.”
However, the increasing weight of cars – as well as torque – is causing tires to wear out faster and harder, rapidly producing more particle pollution. Battery electric vehicles tend to be heavier than conventional, fossil fuel-powered cars. Half a tonne of battery weight can result in tyre emissions that are almost 400 times greater than tailpipe emissions. Despite their zero emissions and their importance in decarbonisation, EVs are potentially generating more tyre particle pollution.
While driving styles are also a factor – ‘aggressive’ drivers can emit up to 5,760 mg/km – there is growing discussion on regulating the wear rate of tyres and on the chemicals that they contain, as well as the need to impose a ‘tyre tax’ on EVs to combat air pollution from them.