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Air pollution: Tyre and brake fatigue compound an exhausting problem

September 8, 2016
Danger ahead

Danger ahead

Shayne MacLachlan, OECD Environment Directorate

Anyone else feeling exhausted by all this drum humming about air pollution? Indeed it appears the fumes won’t be dissipating any time soon as we consider the extent to which tyre and brake rubbish exacerbate the problem. The European Commission says exhaust and non-exhaust sources may contribute almost equally to total traffic-related PM10 emissions. A few months ago, I was proposing (on this very Insights blog) that electric cars are essential in fighting filthy air pollution in urban areas because humans are unwilling to relinquish the comfort of their vehicles. Since then, I find myself mulling hard after this “alarmingly obvious” realisation that electric cars use tyres and brakes too! Even if they emit less of the harmful fine particles than conventional vehicles, please do feel free to file that blog in the “seemed like a good idea at the time” folder. And to turn insult to injury, I see that my own colleagues at the OECD have just published new data on PM2.5 emissions which did little to ease my blushes.

Fine particles vs coarse particles

A lot of non-exhaust pollution from tyres and brakes winds up in rivers, streams and lakes. They produce particulate matter (PM10 and PM2.5) which is more harmful for humans than gas pollutants like ozone and NO2. Fine particulate matter penetrates deep into your lungs and cardiovascular system. New research has even discovered tiny particles of pollution inside samples of brain tissue. The OECD is amongst a few international organisations proudly leading the fight against ambient air pollution. And rightly so, with 80% of the world population exposed to PM2.5. Outdoor air pollution causes 3.7 million premature deaths a year and 1 in 8 people die from filthy air. OECD Environment Director, Simon Upton recently stated that air pollution is not just an economic issue, but also a moral one. He urges governments to stop fussing over the costs of efforts to limit pollution and start worrying more about the even larger costs they will incur if they continue to allow it to go unchecked.

Airpollution 2016 deaths loss 7.9.16

Dead “tyred” but rolling on

Tyre rubbish is the 13th largest source of air pollution in Los Angeles, California, a city famous for its smog. A recent study showed links between PM2.5 particles and the daily death rate in 6 Californian counties. When the PM2.5 count was high, so was the death rate. Then there’s nanoparticles, ultrafine particles used in tyres. Manufacturers didn’t know it at the time but research now contends possible links to lung cancer from recycling some of the 1 billion dead tyres used in, for example, the surfaces of playgrounds. Some are calling it “the new asbestos”. The complexity of the problem is evident: there are over 1 billion cars on the road globally and on top of that just as many motorbikes and scooters. Add to that the pneumatic tyres used on trucks and public transport such as metro train systems and buses and we have a considerable source of road rubber. A road with 25,000 vehicles using it each day can produce up to nine kilograms of tyre dust per kilometre. That’s only ¼ of the 100,000 cars that use the Champs-Elysées each day so that makes at least 36 kilograms of tyre pollution a day on the world’s most famous street.


Bliss ignorance until my tyre burst

When I think back 10 years, sharing my time between the “not so clean” cities of London and Paris, I really had no idea that the air in these places was so bad. I recall often emptying my nostrils of its black contents after using underground transport, but now learning about the added impact of tyre and brake rubbish, I’m not really sure being better informed is better—at least from a personal health standpoint. I have friends in Paris that actively avoid Châtelet and other central metro stations for a number of reasons, one of those being the eye-watering pollution. The metro trains’ brakes and tyres are contributing to this “perfect pollution storm in a subterranean teacup”. Sometimes you can find between 70-120 micrograms of PM10 per m3 down there with peaks at 1,000 micrograms per m3 trapped in the station. In comparison, the average concentration of PM10 outside is around 25-30 micrograms per m3.

So what can we do?

In an ideal world, we would ditch cars completely, but I’m not sure we’re ready to take that step yet. However, several cities are working on implementing policies that will ban or severely reduce the amount of cars. Oslo announced a plan to ban all cars from its city centre in 2019; and Norway is in the process of preparing a bill that would issue a nation-wide ban of the sale of petrol-powered cars. In places such as Tuscany, cars are banned in city centres except for residents. Others park their car just outside and then take public transport. This is common in the UK too. This means that when there are more people in the centre during the day, there are fewer cars, meaning fewer people are exposed. Hopefully, other cities and nations will be inspired by such drastic changes in transportation methods and follow suit. There are certainly enough reasons to do so.

Play the cards dealt and work towards a better hand

It’s hard not to feel we’ve exhausted our current options.  I’ve gone through several cycles of choosing my methods of transportation and have ended up cycling—literally and figuratively. Do bicycle tyres contain rubber (though they emit precious little)? Yes; and so do bus and some metro train tyres, as well as motorbikes and scooters. We are left with only imperfect options. They won’t solve the problem, but they can reduce it and that’s something to be optimistic about. As with many actions that influence health and the environment, human behaviour and choices matter massively. Choosing the least damaging option of getting around your town means the bicycle is still a great option. It might also be worth trying to avoid times in which the pollution levels are the highest: 9h, 12h and 18h in many cities. But of course the exercise and associated heavy breathing whilst riding, exposes you to the risk, even though you are contributing least to the problem. So while the thought of all that damaging pollution is ever so “tyring”, it seems that the pollution, including from brakes and tyres itself might also leave you feeling worse for wear.

An international deal on air pollution

WHO guidelines indicate that by reducing PM10 pollution from 70 to 20 micrograms per m3, air pollution-related deaths could be reduced by roughly 15%. Staging a climate COP (Conference of the Parties) style conference to address air pollution emissions seems like a good start. Who could disagree that setting limits for polluting emissions from all sources is an absolute minimum requirement to give our lungs and environment a breather. Moving forward, it’s crucial we keep pushing governments to come up with innovations and policies that vigorously tackle air pollution issues. Governments also need to ensure that people are aware of the issues and help them make the best choices. In the meantime, we all have to play the cards we’re dealt and make a conscious effort to choose least polluting options.

Useful links

The Economic Consequences of Outdoor Air Pollution

Health Impacts of Road Transport

OECD data on emissions:

4 Comments leave one →
  1. richard penny permalink
    September 15, 2016 01:46

    Can I suggest if the electric cars have regenerative braking – i.e. the engine reverse to produce electricity back to the battery – at least there is less wear on the brakes. So while I agree that electric cars are not a panacea they could be less worse than petrol and diesel cars.

  2. Charles Kovacs permalink
    September 15, 2016 11:44

    After reading this post, my first thought was that this is perhaps some kind of an elaborate insider joke. However, given the reputation of the OECD and its staff, I came to the conclusion that this is serious. In any case, from a laic point of view, I would like to note the following:

    * In articles for public consumption it would be useful to indicate what PM10 and PM2.5 are. Perhaps even NO2, though I remembered that one from high school.

    * A drop in the GDP by 2060 and 3000 deaths per million are not very compelling predictions given what we shall face in the next decade.

    * Footnotes, preferable with a link, would be eminently useful.

    * Yes, we must have types. However, if rubber tires are bad, why not use non-polluting substitutes? They may need to be invented, but it might well work by 2060.

    * I have often travelled on the metro in London and Paris (even stopping and walking through Chatelet), but never noticed any black contents from my nostrils. This surely calls for a study on pollution related nostril emissions of metro passengers in major cities.

    * Another conference is always a good idea, preferably somewhere in the Alps, if only for the sake of the good health and general safety of the participants.

  3. November 11, 2016 14:27

    IIRC road damage from trucks is proportional to the fourth power of the axle loading – anyway it’s (old GAO study, page 23) very far from linear. So a reduction in maximum permitted load per wheel should in theory give a large reduction in road wear. There would be more rubber in contact, but at lower pressure, so the effect on tyre wear could go either way. This needs research.

    Tesla already put a HEPA air filters in their cars. This should be universal, and extended to public transport.


  1. The Tire and Brake Share of Traffic-Related Air Pollution | Pollution Free Cities

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