Is city air bad for your health?

02 November 2015

Interview with

Dr Ben Barratt, King's College London

Regardless of the source, pollution is a serious problem, especially when it comes Nose to our health. So to what extent are we being exposed and what might the risks be? Ben Barratt is a researcher at King's College London who's using cutting edge technology to measure what we breathe in and Graihagh Jackson took it out to see exactly what she breathes in...

Ben - This is called a micro-aethalometer which is a fancy name for a diesel emissions monitor. So, it sucks air in through a tube which mimics your breathing onto a filter and it monitors how black that filter gets as a measure of black carbon. Black carbon is emitted through any combustion process but in cities, it's from vehicles - principally, diesel vehicles.

Graihagh - And that will give an indication of how much I am inhaling as I walk around the streets of London.

Ben - Yes. It takes a reading every few seconds and we'll couple it with a GPS watch so you can see where you are which really visualises the pollution as you walk around.

Graihagh - I should just say it's bright blue. It's a bit bigger than the size of my palm and then it has a rubber tube at the top with a clip which I imagine I'm going to attach somewhere on my blazer.

Ben - So as you say, if you could clip that to your lapel, so that's GPS watch switched on as well. You could put that on your wrist.

Graihagh - I feel like a child being dressed. It's all these pesky radio equipment I've got to carry.

Ben - I like to think of myself more as a doctor than a nursery teacher.

Graihagh - Fully equipped, I hit the streets and I really wanted to put Ben's gear to the test so I pootled along busy roads, swaggered along the river to Big Ben, and then to really give him a run for his money, I got into a black cab.

I literally just want to go to Waterloo.

When I got back to King's College, I've been out for a full hour. Ben loaded the data onto his computer and...

Ben - I've pulled up a map. I've combined the GPS data with your pollution monitoring data and here's a map of your last walk around London. I can see you leaving outside our building, walking along the river for a little while and the levels were really quite low. Then you hit the bridge at Westminster and then something happened and levels shot up. On this map, I can see levels going from a nice yellow to deep red which is not good.

Graihagh - Sort of like a traffic light system. Interestingly, those red sections are actually where I got into a taxi.

Ben - Right. I guessed that's what you'd done because when someone gets into a car and taxis are particularly bad, levels do tend to shoot up quite a lot. Now, if you look at time series of your results we can see these nice low levels along the river, 1, 2 micrograms and then it shoots up. So we've gone from 2 or 3 up to 35 to 40 micrograms. So that's 10 times higher during that taxi journey than afterwards.

Graihagh - That's really surprising because you would've thought being in a taxi, you are more protected from your environment and the air pollution.

Ben - Yes. People assume that inside their little protective box whether it's a car or a taxi, they're protected from the pollution outside but actually, when you think about it, you're sitting right amongst the source of pollution which is those vehicle exhaust and it's coming straight out of the exhaust, in through the air vent of the car, and into the cab of the car itself.

Graihagh - This was measuring black carbon. Specifically, how is that affecting me when I breathe it in? what effect is that having on my body?

Ben - Well in some ways, black carbon is acting as a tracer for vehicle emissions or diesel vehicle emissions in particular. We're still researching what are the components which are most harmful or toxic to health. But there's a mixture of particles, liquids, gases, all of which that come in this cloud of pollutions some of which are coated. So, some of it will be oxidising metals which can attack the lining of the lung. Some of them will be hydrocarbons which are carcinogenic. So, there's a real pea soup of all sorts of chemicals and compounds in there. And then if it gets into your bloodstream, if they're small enough, then that travels around to all of your organs - brain, heart and so on.

Graihagh - And I imagine that changes short term and also long term exposure if I live in London.

Ben - Yes. It's this discovery which has really highlighted the problem that we've got with air pollution, the idea that these pollutants can get into the bloodstream. So air pollution is now linked to cardiovascular effects, cognitive effects, cancers, and so on because you're right. As soon as it gets into the bloodstream, it can get anywhere in the body. There are both long term and short term effects. So, these particles will accumulate over time and have a slow impact on your body - reduced lung growth, cardiovascular problems, and so on. But people who are already susceptible because they've developed some kind of health condition will be affected in the short term. So they may have an exacerbation whether it's an asthma attack or COPD attack or even heart attack.

Graihagh - This is all really frightening.

Ben - It is frightening and what's really striking about it is this is a major public health challenge. But the level of understanding is low compared to other public challenges such as obesity, water quality, smoking, and so on. So, the public needs much more information about the nature of the problem, how they can afford it, and then there'll be more pressure on politicians and policy makers to help clean up the problem.

Graihagh - Obviously, the long term solution is to get rid of pollution altogether in cities. In the short term, what can I be doing? I'm a cyclist so I'm thinking, should I be wearing one of those masks?

Ben - You've seen yourself from your own data, getting into a car is not the way to protect yourself. An active travel is so good for you in so many different ways. So, there's a clear lesson to be learned there about the benefits of walking on quiet roads compared to the risks involved in getting a taxi in London or any other city in the UK.

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