Brake dust is a major source of air pollution and can weaken the immune system, study finds Researchers say brakes a bigger source of particulates in roadside air than vehicle exhausts

Brake dust produces more of the most harmful kind of air pollution than vehicle exhausts, a new study finds.

Researchers have found that the metal-particle dust created by scraping the brake pads accounts for a fifth of tiny particulate pollution on the roads.

By contrast, tail pipe fumes only make up seven per cent of the tiny particles found in roadside air – with the rest coming from sources such as wear and tear on tyres, clutch scrapings and general road dust.

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Air pollution is responsible for an estimated 64,000 early deaths a year in the UK, of which about three-quarters are due to particulate pollution.

Minuscule particles

These tiny particles measure less than 2.5 thousandths of a millimetre across, less than one thirtieth the width of a human hair. They can reach deep into the heart, lungs and bloodstream causing asthma, heart disease, lung cancer and strokes.

They can cause inflammation and weaken the body’s immune system.

Researchers compared the damage caused by particulates from brake dust to that from diesel exhausts by looking at their effect on immune cells.

“Diesel fumes and brake dust appear to be as bad as each other in terms of toxicity. Immune cells protect the lung from microbes and infections and regulate inflammation, but we found that when they’re exposed to brake dust they can no longer take up and destroy bacteria,” said Liza Selley, of the University of Cambridge.

“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,” added Dr Selly, who worked on the study in her previous role at the Medical Research Council’s Centre for Environment and Health.

Macrophages

To test the effect of the particulates on immune cells the researchers grew a type – known as macrophages – that are on the front line of the body’s defences in the lungs, killing bacteria by engulfing and digesting them. They tested them in a lab with Staphylococcus aureus, a common infection in the lungs.

The findings of the study suggest that regulations around brake pollution should be reconsidered, the researchers said.

“As changes in regulations surrounding internal combustion engines takes effect, the relative contribution of brake dust to traffic pollution is predicted to rise. Studies like this could have important policy implications,” said Megan Dowie, head of molecular and cellular medicine at the Medical Research Council.

The study also involved researchers from King’s College London and Imperial College London and is published in the journal Metallomics.