Scientists have discovered that metal particles from the working of brake pads affect healthy immune functioning in a similar way to diesel exhaust fumes — potentially causing coughs, sore throats and, in more serious cases, pneumonia and bronchitis.

The study was published in the journal Metallomics and conducted by a team of scientists from King’s College London.

The researchers obtained dust from a brake pad testing factory under conditions representative of urban driving and high-speed braking.

To test effects on immune cells, the scientists grew macrophages in the lab. (These are a type of immune cell on the front line of our defences in the lungs which kill bacteria by engulfing and digesting them.)

When the macrophages were exposed to particulates from diesel exhaust and brake dust respectively, both reduced the cells’ ability to take up and destroy bacteria. The bacterium used in the test was Staphylococcus aureus, which commonly infects the lungs.

The tests suggested that particulate pollution from brake wear could be contributing to increased susceptibility to airway infections and other negative effects on respiratory health, with vanadium considered by the scientists to be a particular culprit.

Commenting on the study, Dr Ian Mudway, who led the research, said, “At this time the focus on diesel exhaust emissions is completely justified by the scientific literature, but we should not forget, or discount, the importance of other components, such as metals from mechanical abrasion, especially from brakes”.

Dr Liza Selley added, “Worryingly, this means that brake dust could be contributing to what I call ‘London throat’ — the constant froggy feeling and string of coughs and colds that city dwellers endure — and more serious infections like pneumonia or bronchitis which we already know to be influenced by diesel exhaust exposure.”

Last reviewed 13 January 2020