A recent study led by researchers from the University of Southampton in the UK found that pollution from car brake wear can be more harmful to the lungs than diesel exhaust. The study demonstrated that exposure to copper-enriched brake-wear particulate matter has a greater detrimental effect than diesel exhaust particulate matter.
In the paper published in the journal Particle and Fibre Toxicology, the University of Southampton team found that brake-wear particulate matter from copper-enriched non-asbestos organic and ceramic brake pads induced "the greatest oxidative stress, inflammation" on lungs. This brake-wear particulate matter affected a pathway implicated in diseases associated with air pollution exposure, including cancer and pulmonary fibrosis.
"We demonstrate here that brake-wear PM may perturb cellular homeostasis more than diesel exhaust PM. Our findings demonstrate the potential differences in effects, not only for non-exhaust vs exhaust PM but also amongst different sources of non-exhaust PM," said James G. H. Parkin from the School of Clinical and Experimental Sciences at the University of Southampton. "Our results suggest that current legislation, which focuses on PM exhaust emissions, may be inadequate to mitigate the health effects of vehicle-derived PM, and that regulations also need to target not only non-exhaust PM emissions but also specific components of PM," Parkin added.
Ironically, dust from new asbestos-free organic brake pads proved to be the most toxic to lung cells, exceeding the harmfulness of other types of brake pads and even diesel exhaust gases. Researchers identified the high copper content as the main characteristic of brake dust from non-asbestos organic pads.
The researchers examined four different types of brake pads: low metallic with asbestos, semi-metallic, non-asbestos organic, and ceramic. They discovered that the non-asbestos organic brake pads produce the most fine dust.
Non-exhaust emissions, especially from brake wear, represent an increasing component of traffic-related particulate matter and account for approximately 60% of all pollution particles generated by vehicles in the UK. The researchers argued that car brake wear is not included in the target list for exhaust emission reduction measures.
Airborne PM2.5 is known to reach the alveolar regions of the lungs and is associated with more than 4 million premature deaths per year worldwide. Road traffic, particularly diesel exhaust emissions, is a major source of particulate matter in urban environments. However, there is a lack of information about non-exhaust emissions, particularly from brake wear.
Brake-wear particulate matter, particularly from copper-enriched sources, caused perturbation of metabolism, potentially contributing to the development and progression of a range of diseases, negatively impacting healthy living and lifespan.
Researchers have discovered that brake dust pollution, which is not yet regulated, is now the main source of emissions from road transport in many European countries. Several studies have demonstrated that exposure to high concentrations of copper is associated with impaired lung function and an increased risk of death.
In the US, California and Washington have already adopted legislation to reduce the copper content in brake pads. Almost half of the copper in the air we breathe comes from the wear of brakes and tires, highlighting the need for regulation of copper pollution from brake pads.
Moreover, the transition to electric cars will not completely solve this problem. Electric vehicles (EVs) use their brakes less due to regenerative braking, but when they do use the brakes, they emit more fine dust per stop than comparable gasoline cars.
The new Euro 7 standards, which will come into effect in November 2026, will impose limits on brake dust emissions for the first time, potentially stimulating innovation in the development of new materials for brakes or dust capture mechanisms.
The study emphasized that focusing solely on particulate matter from exhaust emissions may be inadequate to mitigate the health effects of vehicle-derived pollution. Researchers emphasize that there is no safe level of exposure to air pollutants.
This article was written in collaboration with generative AI company Alchemiq