In the past couple of years, governments around the world have gone to significant lengths to reduce tailpipe emissions. Lawmakers in the European Union plan to implement a ban on the sale of new piston-powered cars in 2035, and tuners who bypass emissions control systems face multi-million dollar fines. However, a recent study finds that the dust generated by brake pads is worse for your health than exhaust fumes.
Published in the United Kingdom in February 2025, the study analyzes the impact of non-exhaust emissions like road particles, tire particles, and brake pad particles on the lungs. It notes that brake dust—the black stuff that tends to build up on your wheels as your pads wear out—contributes up to 55% of non-exhaust emissions by mass. The problem is that it doesn’t exclusively end up on your wheels; it contaminates water and ends up in the air. The dust’s chemical composition depends on the type of pad but it often includes iron, copper, and zinc, as well as various abrasives, lubricants, and reinforcing fibers. The study notes that there aren’t any laws regulating what can and can’t be used in a brake pad.
Copper is particularly problematic, and somewhat ironically it was introduced in brake pads to replace asbestos, a group of minerals known to cause cancer, among other diseases. Copper is now often found in non-asbestos organic (NAO) brake pads, which is the most common type of pad installed in the United States, and it’s not much better for your health than asbestos. The fine particles that these pads emit as they wear down are linked to diseases such as pulmonary fibrosis, cancer, and pulmonary adenocarcinoma, the study found. The takeaway, according to the authors, is that the fine particles emitted by NAO brake pads can be worse for your health than the fine particles emitted by a diesel engine.
It’s worth pointing out that “diesel engine” is a very, very vague term, and we’re wondering which model was used as a point of comparison. Are we talking about a 1970s Mercedes-Benz 300D, a 1990s Freightliner FLD120, or a Euro 6-compliant BMW 320d? The difference in exhaust emissions is massive.
Mandating electric cars, like the European Union is doing, isn’t going to address pollution caused by brake pads—it may actually make it worse. “This trend is predicted to increase over time, as there is a shift toward heavier battery-electric vehicles which generate more of these friction-derived, non-exhaust emissions,” the study writes. Many EVs are designed to slow down using the drivetrain’s regenerative braking system, not the hydraulic brakes, but that doesn’t mean the pads never come in contact with the rotors. Heavier vehicles go through tires more often, too.
In the European Union, the Euro 7 emissions regulations scheduled to come into effect in November 2026 will limit the amount of fine particles that brake pads can emit. The law sets different thresholds for different types of powertrains, but it doesn’t target copper. “Legislation changes specifically to reduce copper content within brake pads could also be beneficial to public health,” the study’s authors wrote.
The copper content of brake pads is already being addressed in California and Washington, among other states. The Brake Pad Law finalized in 2017 limited the copper content in brake pads to a maximum of 5% in 2021 and a maximum of 0.5% in 2025 for every new car sold in the Golden State. Washington’s Better Brakes Law set the exact same limits and pointed out that 66 metric tons of copper from brake pads enter the Puget Sound marine waterway annually. Several suppliers, including Tokyo-based Akebono, already sell a range of copper-free and low-copper brake pads.
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