Electric cars will not eliminate fine dust pollution caused by tyres and brakes

Electrical cars may eliminate harmful exhaust gases and CO2 emissions, but they will not do away with fine dust pollution, a new study shows.

Researchers from the University of Malta showed that only 3.4% of particulate matter (PM10) originated from car exhaust pipes. Dust caused by tyre and brake friction is an overlooked reality that will not go away with electric vehicles. 

Particulate matter is finely divided solids or liquids that are dispersed through the air via a combustion process, industrial activity or natural process. They are microscopic particles that remain suspended in the air.

Exposure to such particles can affect both lungs and the heart. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including premature death in people with heart or lung disease.

The researchers found that non-exhaust emissions contributed to 35% of the particulate matter collected in their experiment on Malta’s roads.

Non-exhaust emissions are caused by friction between the tyre and road surface, the resuspension of dust particles previously deposited on the road, and the abrasion between the brake pad and the wheel. 

Road dust or ‘crustal’ contributed to 18% of the findings, while tyre and brake wear contributed to 17% of the collected matter. 

Marine aerosol (23%), Saharan desert dust (21%), secondary sulfate aerosol (9.4%) and aged marine/shipping aerosol (8.9%) were the other contributors.

To understand which sources could be contributing to the emissions, researchers from the Institute of Earth Systems collected data at an Msida traffic site with a sampler over the course of a year. 

The collection site forms part of the Maltese air quality monitoring network operated by the Environment and Resource Authority. Samples were collected between 19 January 2018 and 31 December 2018. 

The particles collected were then chemically analysed to identify their source. 

Tyre and brake dust

Matter stemming from exhaust tail pipes consists mainly of iron particles from engine corrosion, zinc from car catalytic convertors, and black carbon. Tyre and brake dust on the other hand has large amounts of copper and heavy metals. 

Exhaust material is normally finer and is associated with long term health complications, while larger particles from tyre and brake dust cause short term damage. 

The findings may expose gaps in environmental policy related to the use of private cars and public transportation. 

Malta is among other countries pushing for the transition from internal combustion engines to electrical vehicles. Transport Malta recently launched a €15 million scheme aimed at encouraging the use of cleaner and more sustainable forms of transportation.

The initiative will support the purchase of new electric vehicles in EU Category L, M and N, including passenger cars, vans, goods-carrying vehicles, minibuses, coaches, quadricycles, motorcycles, and pedelecs.

MaltaToday reached out to Mark Scerri, one of the researchers behind the study, who explained that results showed the need for a multi-faceted approach to combat climate change. 

“The study shows that just switching to electric vehicles will not solve the issue, but it should not be interpreted as an excuse to retain internal combustion vehicles,” he said. 

Scerri said the solution lies in incentivising mass public transportation. 

“Government must disincentivise car use, and push for public transport,” he said. “Making public transport free for commuters is not enough, money was never the problem.”

The university lecturer said a change in mentality and culture is much needed to address the problem. 

“Look at the recent controversy surrounding e-scooters. Instead of criticising government for not providing the needed infrastructure, people criticised commuters seeking an alternative mode of transport for not finding where to park them,” he said. 

Scerri said he hopes the research helps policy makers in taking a broader approach in seeking solutions to climate change.