Car brakes contribute to air pollution

How do car brakes make pollution worse?
14 January 2020

Interview with 

Liza Selley, University of Cambridge


3D map of an electric car model


Air pollution is an increasingly large problem. According to the World Health Organisation, as many as one in eight deaths worldwide are linked to poor air quality. One kind of air pollution is called particulate matter, made up of any tiny particles in the air. But not all of it comes out of the exhausts of cars. Some of it comes from vehicle brake pads. The impact of that is the subject of new research in the journal Metallomics. Liza Selley joined Adam Murphy and Chris Smith to explain...

Liza - It's a little bit like when you sand wood with sandpaper, when the driver puts their foot on the pedal, two metallic components come together near the wheel. You have the brake disc and the brake pad, and when they come together it produces a lot of heat and a lot of friction and this wears away at the components and they release these metallic particles into the ait.

Adam - And why is that bad? What damage does that do to us?

Liza - These particles are really tiny, kind of like cigarette smoke. They're small enough to get deep inside the lung. They can cause a massive inflammatory response in the immune cells whose job it is to clear the lung of infection, and they can actually prevent those cells from taking up bacteria and killing it.

Chris - Do you know Liza, why the brake dust, or the metal particles stimulate the immune system and specifically the these macrophage cells and the immune system in this way?

Liza - Actually we've seen that other cells in the lung can be affected in a very similar way, but the metals are able to react with proteins, DNA, fats inside the cells. And this can affect the way that they function. And that goes on to have an effect on the cell's behavior.

Adam - And then what's the consequences of this short and longterm?

Liza - Short term, people get a lot more coughs, sore throats, asthma attacks. In the longterm, we worry a little bit about lung cancer and also development of infections like pneumonia. And that's just the lungs. People are looking at all sorts of different organs in the body.

Chris - And is it just the particles from brakes that could do this? What about vaping? Because that's tiny particles as well, isn't it?

Liza - Yeah, you're right. My colleagues at Kings College have looked at vaping and they've measured metals inside of it. That means it is a cause for concern.

Adam - Are there any recommendations that come off the back of this? Anything we can and should do to help?

Liza - So for you and I, everyday people, things we can do are try and reduce the amount of times we go out in the car. So I'm trying to do a weekly shop rather than go daily, which is quite difficult for me. But I'm trying my best. Things like sharing lifts, if you can, just trying to get your car off the road as much as possible.

Chris - I think that's good advice in all circumstances, isn't it Liza but, when one looks at the levels to which one is exposed in the air in a busy street, how does that compare with the levels of these things that you put onto your cells?

Liza - The air outside will be lower than what we're putting on our cells. But the reason we've got it this high is the nature of our experiments, we want to know why it's happening. So we need to see the response.

Chris - And that's kind of a worst case scenario, so it could be that actually we're not as much at risk, but if you walk down a very busy street in London at peak, you might be exposed potentially to the levels that you're testing.

Liza - Exactly.

Chris - And it's an indicator, excuse the car analogy, that actually there is a risk and as traffic densities rise we need to take more care.

Liza - Yeah, I agree.


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