Do electric cars have a problem with air pollution? | Car industry

TOxic smog has been part of life in big cities since the Industrial Revolution: a pea-soup blanket of harmful particles that can be so thick that it makes seeing and breathing difficult. But in many cities across the rich world, that dirty body has been banished as car engines have become cleaner and factories have moved. (Poorer cities are not so lucky.)

Some people believe the shift to electric cars could reverse some of that progress: that heavier cars and the particles they produce through friction mean we may sacrifice cleaner air on the altar of zero carbon emissions.

In its EV mythbusters series, The Guardian has investigated claims about electric vehicles (EVs), looking at issues ranging from CO2 emissions and battery fires to the idea that hydrogen will overtake them. The latest in our series asks: Do electric cars have an air pollution problem?

The claim

Electric cars reduce engine pollution to zero, but their brakes and tires still rely on friction to work. This friction breaks down materials, which can then end up in the environment. Some people argue that the shift to electric vehicles, which tend to be heavier and therefore cause more wear and tear, could lead to an increase in overall air pollution.

In 2022, Britain’s then Environment Secretary George Eustice expressed “skepticism” to parliament about air quality improvements. “Some say the wear and tear on the roads and the fact that these vehicles are heavier means the profits may be less than some people hope, but at the moment this is somewhat unknown,” he said.

The Daily Mail reported that tire pollution was the “dirty secret of electric cars”, while the Sun reported that “EV drivers have been warned about ways their super-heavy electric cars end up causing MORE pollution than petrol and diesel engines”.

The science

EVs do not directly burn fossil fuels – and would produce no emissions at all if they were produced exclusively with carbon-free energy. In addition to carbon dioxide, this means that there are no emissions of carbon monoxide, nitrogen oxides and a cocktail of carbon, metals and unburned hydrocarbons in built-up areas. (Fossil fuel power plants still pose a problem for charging electric cars, but in richer countries they tend to be located far away from population centers.)

However, all cars produce particulate matter (PM) from friction on the brakes, tires and road surfaces, leaving a dusty trail of pollution in the air and on the ground. That pollution contains harmful chemicals: one additive, washed from roads into rivers, was found to be the cause of the mass die-off of coho salmon on the US West Coast.

Brakes and tires rely on friction to work, which breaks down materials. Photo: ftwitty/Getty Images

In terms of braking, electric cars generally produce less particulate matter because they use regenerative braking to stop, said Euan McTurk, a battery chemist who has been investigating the particulate matter problem for the RAC. EV brakes wear out much more slowly, he said.

But electric cars do have a case for roads and tires, because greater weight means greater wear and tear. Transport & Environment, an action group, has calculated that electric cars are on average about 400 kg heavier due to the large batteries.

Many of the claims about electric vehicles causing air pollution are reference figures from Emissions Analytics, a private company. Founder Nick Molden said measurements show particulate matter emissions can be 1,850 times higher than those of modern car exhausts, which have become cleaner through regulations. But this key finding needs some context: The tests have not been peer-reviewed by scientists, and the industry disputes the findings.

Crucially, all cars produce these pollutants – not just the electric versions. Measuring small particles is very difficult and there have been relatively few comparative studies to date. That means there is still uncertainty about whether the extra weight of EV batteries will result in greater particulate matter pollution.

The shift to SUVs means vehicles are becoming bigger, wider and heavier, which will worsen CO2 emissions. Photo: Mike Kemp/In Images/Getty Images

German tire manufacturer Continental said that the design of the vehicle and tire is less important in determining wear than driving style and the curves of the road (a point also made by Molden). A Continental spokesperson said: “In principle, EVs do not produce more particles than an otherwise comparable internal combustion engine vehicle simply because of the higher weight caused by the battery.”

There are a lot of moving (and rubbing) parts in any calculation, but there have been some attempts to add it all up. A 2020 study by the Organization for Economic Co-operation and Development estimated that “the introduction of electric vehicles will lead to a very marginal reduction in total PM emissions from road traffic in the coming years.” The study found that heavier electric cars cause marginally more road and tire wear for the larger PM 10 particles and the smaller PM 2.5. But once engine pollution is added in, petrol and diesel cars were marginally worse.

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Any comments?

There is broad agreement that tire pollution is still harmful. Many scientists believe that smaller PM 2.5 particles are more harmful because it can enter the bloodstream and end up in the brain or placenta.

Tire makers are looking at adjustments in their chemistry. The Tire Collective, a British startup, has an elegant potential solution: an electrostatic device that captures tire particles so they can potentially be recycled into new tires.

“Tyre wear has always been a problem,” says Hanson Cheng, the founder of the Tire Collective. “It’s just been overshadowed. You can’t really claim the title of zero-emission vehicle when there are all these non-tailpipe emissions.”

All car tires produce pollutants when they are worn – not just the electric versions. Photo: Aitor Diago/Getty Images

Whether gasoline or electric, tire pollution will get worse if the SUV giant continues. Cars are becoming bigger, wider and heavier (which will worsen CO2 emissions and energy efficiency).

Anna Krajinska, Transport & Environment’s vehicle emissions and air quality manager, said there is no conclusive evidence that electric cars will increase particulate emissions, but added that we should try to limit the shift to SUVs.

The verdict

There is no doubt that the auto industry still needs to answer questions about pollution. As the end of the internal combustion engine approaches, expect more attention to particulate matter pollution from tire wear, as this is one of the few sources of pollution while the car is in use. This can provide major health benefits for people, flora and fauna.

It is certainly true that increasingly heavier cars almost certainly produce more tire dust. Electric cars are – for the time being – even heavier than comparable cars. Yet tire pollution appears to be roughly comparable between petrol, diesel and electric cars. The other benefits of switching to electric cars – particularly lower CO2 pollution – are enormous.

Combating air pollution is an important cause, but does not seem to provide a reason to postpone the transition to electric cars.

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