The impact of air pollution is linked to approximately seven million premature deaths annually worldwide. When we think about air pollution in cities, emissions from diesel engine exhausts are often portrayed as the main culprit – and this is correct, given the results of previous studies. However, our latest research shows that dust from brake pads may be more harmful to our lungs.
The dust created from the wear of roads, tires, and brakes, known as "non-exhaust emissions," is now the dominant type of vehicle emissions, surpassing exhaust emissions in many European countries. Among these, brake dust is often the main factor, but it is not yet regulated. Little is known about the potential health impacts of brake dust compared to diesel exhaust particles.
We grew cells in the lab to simulate lung tissue and exposed them to both brake dust and diesel exhaust particles. Brake dust turned out to be significantly more harmful to these cells in various indicators related to lung diseases such as cancer and asthma. Interestingly, we found that removing copper from brake dust reduced these effects.
Despite this, current vehicle regulations in the UK focus solely on exhaust emissions. Our findings suggest there is an urgent need to consider regulating non-exhaust emissions. Changing the composition of brake pads could be one way to reduce the potential health burden caused by these emissions.
Brake pads previously contained asbestos fibers to combat overheating. However, asbestos was banned in the UK in 1999 due to its association with lung diseases. This led the automotive industry to develop new brake pad linings, including non-asbestos organic (NAO) pads, which are widely used in vehicles today.
We compared the harmfulness of dust from the wear of different types of brake pads. Ironically, we found that the dust from NAO pads, designed to replace asbestos-containing linings, was the most toxic to lung cells compared not only to dust from other types of linings but also to diesel exhaust particles. Some of the effects on our cells are related to diseases such as lung cancer, pulmonary fibrosis (scarring of the lungs), asthma, and chronic obstructive pulmonary disease.
Previous studies have shown that metals in air pollution particles can be toxic. We measured the metal content in various types of brake dust and diesel exhaust particles. Artificial intelligence methods identified a high copper content as a characteristic of brake dust from NAO pads.
We also found that this copper could enter lung cells. Most interestingly, when we treated this brake dust with a chemical to neutralize the copper, its toxic effect decreased. This suggests that copper is responsible for at least some of the harmful properties of this dust.
Almost half of all copper in the air we breathe comes from the wear of brakes and tires. Various studies conducted by other research groups have shown that exposure to high concentrations of copper is linked to impaired lung function and an increased risk of death