A main cause of air pollution is car exhaust, yet new research is helping to highlight another traffic-related pollutant. Pieces of tyres and brake pads are chipped away, turning into a fine dust. This road dust is thought to contribute towards health concerns, according to a study carried out by the University of Pennsylvania’s Reto Giere.
Giere has worked with people all over the world to conduct his research. “More and more I’ve noticed that we don’t know enough about what is on our roads. If you have lots of traffic, cars and trucks driving by, they re-suspend the dust on the roads into the atmosphere, and then it becomes breathable. To understand the potential health implications of these dust particles, it’s really important to understand what’s on the road.”
Regulations have helped to make cars more environmentally friendly. But the restrictions haven’t taken into consideration the damage that tyre and brake debris can cause. In order to detail the harmful effects of road dust, Giere teamed up with German colleagues from the Federal Highway Research Institute and the University of Freiburg. In 2017, they published the findings of samples they’d taken from German motorways.
When it came to collecting the dust, Giere and his team used customised cylindrical samplers with a transparent sticky foil at the bottom. This trapped particles that floated inside. The sticky ‘trap’ was changed weekly. Then, the team utilised optical microscopy to analyse the particles. They found that congested sites had 30% more particles overall, with a large amount coming from tyre wear. Giere said “at higher temperatures we saw more tyre abrasion, more pollution than at intermediate temperatures. This was exactly analogous to what two laboratory studies found.”
A more recent study involved Giere using electron microscopy to identify the make-up of the collected particles from the 2017 study. The analysis found the particles to be made up of a mixture of tyres and minerals that became attached from the road. Tyre and brake pads are known to be made from materials like lead, cadmium, asbestos and silicates, all of which pose a potential threat to the environment.
Giere summed up the research. “These coarse particles aren’t going to be transported very far, so pollution is going to be restricted to the vicinity of these roads, especially during congestion. But they do also collect on the road and then wash into rivers. Our team believes that’s a major pathway of how microplastics get into waterways.”
A way to reduce road dust pollution would be to look into lowering road congestion. Giere’s research has shone a light on an avenue that people might not have considered to cause pollution.
