Airborne pollution: the silent killer.
Much of my working life is spent in London and I cycle everywhere. It’s a fast, convenient way to get around, but I do worry about the air I’m breathing. When it comes to air pollution, London comes out badly. So what is the best way to get around a busy city if you want to minimise your exposure? Walking, driving, cycling, or the Underground?
The story around air pollution is confusing. Six years ago I bought a diesel car. I’d read that diesel produces less carbon dioxide per mile than petrol, so I thought I was doing my bit for the environment. It turns out that I’ve been contributing to the nearly 40,000 premature deaths that happen every year in the UK as a result of air pollution. This is more than 20 times the number of people that die in road accidents and is only exceeded by the 80,000 who die every year as a result of smoking.
The trouble with diesel is that it produces a lot of nitrous oxide, which irritates the lungs, and ozone, which is also bad for the lungs. Ozone is formed when nitrous oxides and other volatile organic compounds react with sunlight, so levels can get spectacularly high during the summer.
As well as these gases, diesel engines produce lots of tiny specks of particulate matter (PM). These specks are so small that they can penetrate deep into your lungs, carrying with them a host of unburnt combustion components. These in turn trigger reactions that damage your blood vessel walls, contributing to heart disease, type 2 diabetes and Alzheimer’s.
So when I’m cycling around London I’m inhaling all this stuff, which has to be bad for me. But how bad is bad? To find out I took to the streets of London wearing a pollution monitoring device. I walked from the Strand to Marble Arch, a distance of about five kilometres (three miles). Then I cycled back, but taking quieter back streets.
Finally, I jumped into the back of a taxi and went another five kilometres, this time through relatively heavy traffic.
So what happened? Well, when I walked to Marble Arch the route I took was congested with buses and taxis, and the device I was wearing recorded an impressive rise in the levels of pollutants in the air I was breathing. When I returned down the back streets on my bike I was reassured to see that the levels dropped off really dramatically.
But the highest spikes, suggesting the worst levels of pollution, were when I was sitting in the back of the taxi. That’s because if you are sitting in a car in traffic then the air inlet of your vehicle is going to be right behind the exhaust pipe of the vehicles in front.
You can turn off the air inlets and close the windows, which will make some difference, but the fact is that when you are stuck in traffic you are sitting in a giant pool of invisible pollution to which you are also contributing.
I didn’t try travelling on the London Underground, but I suspect that if I had then the results would have been even worse. A study last year by the University of Surrey found that people travelling by the Underground were breathing in far larger amounts of damaging PMs than those who were travelling by bus or car. So I am delighted to say that cycling is not only incredibly convenient but also one of the best ways of travelling around while avoiding air pollution.
You could spend a lot of money on a sophisticated mask with active charcoal filters that will take out the gases, but you’ll still be breathing in tiny particles. My best advice is to do what I do now, and take the quiet back streets. It takes a little longer, but it makes me appreciate what a wonderful city London is. Despite the pollution.
“I DO WORRY ABOUT THE AIR I’M BREATHING WHEN I’M IN LONDON”
Michael Mosley is a science writer and broadcaster, who presents Trust Me, I’m A Doctor on BBC Two. His latest book is The Clever Guts Diet (£8.99, Short Books).