Dust from Car Brakes More Harmful than Exhaust, Study Finds

In cars, pollution doesn’t come from exhaust alone. It also comes from wear and tear on roads, tires, and brakes. According to new research, tiny bits of dust cast off by brake pads may inflict more harm than car exhaust.

For the study, published in Particle and Fibre Toxicology, researchers grew human lung cells in a lab and exposed them to dust from car brakes and from diesel tailpipes, finding that brake dust caused greater injury to the cells.

Surprisingly, newer brake pads proved more harmful than older ones, which were made with asbestos. Asbestos, which is known to cause cancer, was used to stop brakes from overheating. While newer pads are made without asbestos, they contain high levels of copper, which can aggravate asthma and raise the risk of an early death when inhaled. Researchers found they could minimize the harm from newer pads by treating brake dust with a chemical that neutralizes copper.

California and Washington have both passed laws to limit the use of copper in brake pads, but brake dust remains largely unregulated. The new study, authors write, highlights “the need for targeted legislation to protect public health.”

Researchers note that the shift to electric vehicles could curb pollution from brake pads. Most electric cars use regenerative braking, in which the car motor turns into a generator, drawing energy from the spinning wheels as they slow to a halt. This limits the need for conventional brake pads.