As sales of zero emission electric cars surge across Europe and the end of the internal combustion engine is in sight, the industry is clutching at straws to keep the polluting engine alive.
Toxic emissions from tailpipes of diesel and petrol cars have caused air pollution problems in European towns and cities for decades and cause tens of thousands of unnecessary, premature deaths each year. Now, as sales of zero emission electric cars surge across Europe and the end of the internal combustion engine is in sight, the industry is clutching at straws to keep the polluting engine alive. One claim, covered in a number of newspapers, is that electric cars will make air quality worse due to particle emissions from non-exhaust sources, such as tyres and brakes. This is wrong.
Here’s why.
First, conventional internal combustion engine (ICE) cars mainly use disc brakes to slow the car down and this emits particle pollution. Electric cars on the other hand are able to use the electric motor for braking, reducing the need to use the brakes and therefore reducing particle emissions. This process is called regenerative braking as it restores braking energy back to the car’s battery, where it can be used to power the car. While there is little data at present on the particle emission saving from using regenerative braking, it is expected that this technology will result in a large reduction in particles as electric cars seek to use regenerative braking as much as possible to increase the electric range of the car.
When it comes to tyre pollution many reports suggest that switching to BEVs will increase particle pollution due their heavier weight compared to conventional cars. However, there is yet to be a comprehensive study measuring particle emissions from tyres, especially of electric cars. It is often forgotten that electric cars are mostly fitted with special tyres designed to cope with the specific needs, including the heavier weight, of BEVs to ensure that they do not wear out too quickly. Therefore, studies which make assumptions on tyre emissions from BEVs on the basis of normal tyres are potentially overestimating the problem. And Blaming BEVs for tyre pollution when all road vehicles – including heavy SUVs – are to blame, is wrong.
Most comparisons of particle emissions from BEVs and ICE cars only focus on ‘primary’ particle mass (PM) emissions – those particles which are emitted directly from the exhaust, tyres and brakes. However, they fail to take into account the ‘secondary’ particle pollution also caused by ICE’s. These particles are not emitted directly out of the tailpipe but form in the air due to other pollutants such as nitrogen oxides (NOx), hydrocarbons (HC) and ammonia (NH3) emitted from the tailpipe. Like primary particles these ‘secondary’ particles also contribute to PM2.5 (particles smaller than 2.5 microns) and PM10 (particles smaller than 10 microns) pollution, thereby worsening air quality. According to a recent study by the Organisation for Economic Co-operation and development (OECD), these secondary particles can contribute up to 29% of the total PM emissions of a car, so ignoring them can greatly underestimate total PM pollution of ICE cars.
Most importantly, the OECD study found that when all particle sources associated with cars are counted, including secondary particles, BEV passenger cars and SUVs contribute less PM2.5and PM10 than diesel or petrol cars. PM emissions are reduced by 6-42% on switching to a BEV from a conventional ICE car, depending on the size of the BEV and which car it replaces (for example a bigger decrease is seen for diesel cars).
A reduction is seen even for heavier BEVs with a longer electric range of 460km, enough to get from Brussels to Frankfurt in a single charge. Cars currently on sale with this range include the Kia e-Niro (451 km), Hyundai Kona Electric (445km) and the Jaguar i-Pace (467km). This indicates that even heavier, longer range EVs will have a positive impact on air quality.
Switching from an ICE to a BEV instantly eliminates all toxictailpipe pollution such as nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC) – not just particles. This is down to there not being a polluting combustion process. As these pollutants are only emitted from cars, out of the engine, if there is no engine there are no emissions.
One of these harmful pollutants, nitrogen dioxide (NO2), is responsible for over 50,000 premature deaths per year in Europe. It causes respiratory and cardiovascular disease and can be a death sentence for those suffering from asthma. Recently, a UK court ruled that air pollution, including NO2, contributed to the death of Ella Adoo-Kissi-Debrah, a nine-year-old asthma sufferer living in London. She was living just 30 metres away from the South Circular road – one of the city’s busiest and most polluted.
NO2 is a big problem in cities where heavy traffic emits toxic fumes right next to where people breathe, go to school and live. Nitrogen oxides (NOx) emissions from conventional cars, which includes both NO2 and NO (NO is converted to NO2 in the air and therefore both gases contribute to air pollution), is the main reason why many urban areas in Europe are still choking on air that exceeds legally mandated air quality limits.
ICE car engines also emit other pollutants which contribute to poor air quality. These include carbon monoxide, hydrocarbons, ammonia as well as other less known but toxic and cancer causing chemicals including benzene and polycyclic aromatic hydrocarbons. Car makers themselves acknowledge that it is not possible to eliminate harmful emissions from the engines of conventional cars. There is no technology available which can completely remove pollutants made during the combustion process before they are emitted out of the exhaust. Even future e-fuels (made from renewable electricity instead of fossil fuels) will not solve the problem.
Therefore, the only option for eliminating emissions of these harmful pollutants from cars is to switch from engines to electric motors. The quicker this happens, the sooner the air quality benefits will be felt across Europe.
Expected improvements to air quality due to switching to BEVs do not mean however that non-exhaust pollution should be ignored. Instead of demonising EVs and trying to slow down the transition to electric mobility, which will improve air quality for all, particle pollution from brakes and tyres should be reduced from all cars as quickly as possible through smart regulation.
A method for measuring brake wear emissions is already being developed by the UN Particle Measurement Programme, so soon emissions from brakes can be accurately measured. Technologies for reducing brake wear emissions are already available. The EU funded LOWBRASYS and REBRAKE projects succeeded in reducing particle mass emissions from brakes by over 50%, while French company Tallano has developed a ‘vacuum’ brake pad which claims to remove 85% of braking PM. The upcoming EU pollutant emission standard currently in preparation (“Euro 7”), should set a brake particle limit for all cars regardless of their powertrain. This will drive innovation and adoption of low emission brake technologies and reduce their contribution to air pollution for all cars.
For tyre wear particles the latest EU tyre labelling regulation (2020/740) requires the European Commission to develop a method for measuring tyre-wear emissions and subsequently to assess the feasibility of adding abrasion and mileage information to tyre labels. This is something NGOs like T&E, as well as many cities, have been calling for, for years. T&E now recommends that the Commission goes one step further and bans the sale of the most polluting and least durable tyres from the EU market, since these have a disproportionately negative effect on air quality.
BEVs therefore do not produce more air pollution than fossil fuel cars. In fact they eliminate emissions from engine exhaust and significantly reduce emissions from brakes. The evidence on tyres is more mixed but claims that battery cars create more particle pollution due to tyres are misleading as they ignore the overall air quality benefits of EVs. Particle emissions should not be used as an excuse to slow down the transition to zero emission mobility which will beyond doubt improve air quality across Europe. Instead, regulation should address pollution from brakes and tyres to ensure that emissions from these sources are reduced for all road vehicles.
