A new British study suggests that microscopic particles from brake pads could be more toxic than emissions from diesel engines. This finding raises concerns about vehicle pollution, even as the world shifts to electric cars.
Researchers discovered that certain brake pad materials—especially those containing high amounts of copper—can cause significant harm when inhaled into the lungs. These tiny particles, released when brakes wear down, can trigger inflammation and other health issues.
While past efforts to reduce vehicle pollution have focused mainly on exhaust emissions, this study highlights a growing concern: "non-exhaust" emissions, which come from brakes, tires, and road wear. These sources are now the largest contributors to vehicle-related air pollution in the UK and parts of Europe.
Key findings
Dr. James Parkin from the University of Southampton, the study’s lead author, emphasized that most people assume car pollution comes from exhaust pipes, while electric vehicles are considered “zero-emission.” However, electric cars still create pollution through friction from tires, roads, and brakes.
The study analyzed four types of brake pads, testing their effects on human lung cells:
- Non-asbestos organic (NAO) brake pads – The most toxic, causing the highest level of inflammation and lung damage.
- Ceramic brake pads – Also harmful, but slightly less than NAO pads.
- Low-metallic brake pads – Moderately toxic.
- Semi-metallic brake pads – Had the lowest toxicity levels.
Surprisingly, NAO brake pads were found to be more harmful than diesel exhaust particles in their effect on lung cells.
Experts weigh in
Dr. Ian Mudway from Imperial College London acknowledged the study’s value but warned against jumping to conclusions. He noted that many factors—such as different brake disc types and diesel exhaust particle variations—were not accounted for in the research. He also pointed out that tire wear and road dust should be considered as other major sources of vehicle pollution.
Professor Matthew Loxham, a project supervisor, agreed with this criticism but defended the study, explaining that the brake particles were tested under standardized conditions, making them a realistic representation of real-world pollution.
Policy implications
This research suggests that policies focusing only on reducing exhaust emissions will not be enough to solve the problem of vehicle-related pollution. As more people switch to electric cars, addressing non-exhaust sources of pollution—such as brake and tire wear—will become even more important for public health.