Podcast: Measuring pollution from the BT Tower

London smog

28 May 2013 by Sue Nelson

This week in the Planet Earth podcast, James Lee of York University tells us about a UK project which is the largest and most comprehensive effort yet to investigate air pollution across London, while Frank Kelly of King's College London describes the link between traffic, pollution and disease.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Sue Nelson: This time in the Planet Earth podcast, measuring urban pollution and its effect on our health. I'm Sue Nelson and as you can probably tell from the traffic noise I'm in a city - London in fact - at the base of the iconic cylindrical BT Tower. Dr James Lee is with me from the National Centre for Atmospheric Science at the University of York and he is one of a number of scientists who are collaborating on a project called 'Clean Air for London' or ClearfLo.

Dr James Lee: ClearfLo is a consortium of UK universities and research institutes looking at the emission and chemical transformation of air pollutants in London.

Sue Nelson: So why are we at the base of this BT Tower - not that I don't appreciate seeing it above me?

Dr James Lee: We've got a series of instruments 150 metres above us on a platform looking at the pollutants above the streets of London.

Sue Nelson: Right, well, in that case we had better go and have a look at these instruments.

We're inside now and walking around the circular corridor to the north lift. So, going up to the 35th floor, you said about 150 metres high. I looked it up the BT Tower is 189 metres high; we pretty much almost near the top.

Dr James Lee: And the instruments sample their air from the very top, so we have a sample pipe that goes to the very summit of the building and we pull air down to the 35th floor which is where our instruments are actually sat.

Sue Nelson: Well, my ears are going slightly popped there beneath my headphones, so I'm quite glad we're reached... that was very quick to go 35 floors. Good grief!

We will just carry on walking past a load of bays and electronic equipment and racks and I can't help noticing what a magnificent view it is from up here. It looks like we're overlooking Regents Park this side that we're on. Where is your instrument? Is it outside or inside?

Dr James Lee: The instrument I personally look after is in here, in this rack. I will just open the door for you - this bank of kit down the bottom here.

Sue Nelson: Which almost looks like an old fashioned stereo.

Dr James Lee: Indeed.

Sue Nelson: And what does this instrument actually do or measure?

Dr James Lee: These instruments measure nitrogen oxides. So nitrogen oxide - NO - and nitrogen dioxide - NO2 two of the main air pollutants in London, or in any city in fact. The pipes that you see are drawing air from a main sample manifold right at the tope of the tower, about 30 metres above our head. This was the highest place we could actually site he instruments. There are quite a lot of them. We need a lot of power and they need to be kept cool, hence why they're in this room rather than at the top themselves.

Sue Nelson: Where does the nitric oxide come from?

Dr James Lee: So nitric oxide is essentially produced in any form of combustion and that as we're above a city here almost all the nitric oxide we're seeing here will come from the exhaust of cars and trucks and busses.

Sue Nelson: So why don't you have this instrument at ground level?

Dr James Lee: There are a lot of monitoring stations at ground level dotted around London - 50 or so. What we're trying to do here is to get away from the actual point source of the street and get above them so we can get an idea of the actual total emission from London. We suspect the footprint we've got of emissions here stretches round about five kilometres from the base of the tower. There are some uncertainties with the estimated emission rates of nitrogen oxides from London. There are kilometre grid squares where there is an estimated amount of these gasses omitted and what we can do here, well hopefully what we can do here with the data, is to provide an actual measurement of that to compare with the emissions.

Sue Nelson: And why are these so important? Why is it so important to get accurate measurements of these gasses in the UK?

Dr James Lee: Two reasons really. The species themselves, particularly nitrogen dioxide is poisonous to humans. There are quite strict limits on how much of this gas is allowed to be in the air. At the moment the UK isn't meeting these targets but also they go to form ground level ozone which is another dangerous pollutant, so the action of sunlight on nitrogen oxide and nitrogen dioxide forms low level ozone.

Sue Nelson: Now because we're in the part of the BT Tower that's facing northbound, I can't quite see where I met Professor Frank Kelly from King's College London earlier on. He's near Waterloo and is part of a group that runs the London Air Quality Network and four of their 150 monitoring sites in the capital were used for the ClearfLo project. Professor Kelly is specifically interested in the health aspects of the work that is being done here on the BT Tower and across London, so we met up to discuss what types of problems urban pollution can cause.

Professor Kelly: The current government figures are that approximately 29,000 people each year die prematurely or lose some of their lifespan because of pollution in the UK, and of course that's really just the tip of the pyramid because below that we have many, many more people who are being influenced by pollution in respect of maybe the nature of their disease they develop or the exacerbation of that disease if it's a respiratory disease, how often it occurs on a weekly basis.

Sue Nelson: Are they most respiratory diseases that pollution causes?

Professor Kelly: We thought originally that it was because it would be logical to think that whatever you breathe in is going to affect your lungs. That is true to a certain extent but what we've begun to realise over the last few years is that in fact it goes beyond the lung and in fact because simply of numbers cardiovascular disease, which has now been linked to air pollution exposure is by far the largest disease related pollution affect.

Sue Nelson: And what sort of particles? What sort of pollutant particles are the main causes of these respiratory diseases?

Professor Kelly: In urban environments it appears as if traffic is a major source of the particles which we associate with these problems. Primarily we thought that it was to do with emissions from exhausts and it appeared again that the type of car or vehicle involved was important, so those that ran on diesel produce a lot more particulate matter than petrol vehicles would. So there was considerable worry about that. More recently there has also been attention paid to non-exhaust particle generation by vehicles and here I really mean the particles that are generated from the use of clutches and brakes and tyres as they run across the road and some small particles are released in that process, so in fact it is the totality of the vehicle emissions which seems to be the problem.

Sue Nelson: The diesel one is a slight surprise to me because it is always sold, or being sold as an environmental friendly option.

Professor Kelly: Correct. This is really a major confusion. So diesel use in this country has been encouraged because of the climate change agenda and because diesel cars are a little bit more efficient then of course then you require less fuel and produce less CO2 if you have a diesel than a petrol car. But, unfortunately diesels from a pollution point of view produce, we think, currently about 20 times more particles than a petrol car would. So, good for climate change, bad for air quality.

Sue Nelson: Now you've got two years worth of pollution data, what are you going to do with that?

Professor Kelly: The two years of pollution data is a very special data set because it has been enriched in a number of ways which has not been available to health researchers before. So we've got very detailed hourly information on the size and chemical nature of particles across London. Before we really only had very rough information on the mass of particles, not much about their chemical composition. So now we're going to be able to use that data set to link to health sets and to ask the questions which type of particles and which components on those particles seem to be most linked to health effects that we see.

Sue Nelson: Professor Frank Kelly from the Environmental Research Group at King's College London.

Well I've now come outside the top of the BT Tower with Dr James Lee around the other side from where your instrument is, so we're looking across at the City and the Gherkin and Canary Wharf, the London Eye, the Shard, it's rather magnificent but, James, Frank spoke about the issues concerning diesel particulates. Now you're measuring nitrogen oxide, so what other pollutants are being monitored here?

Dr James Lee: We're monitoring some other air pollutants - carbon monoxide, which is another pollutant that comes out of car exhausts. We're also measuring some greenhouse gases, methane and carbon dioxide just to assess London's effect on greenhouse gas and not specifically air pollutants but just a different environmental atmospheric issue.

Sue Nelson: Dr James Lee from the University of York, thank you very much indeed and I will let you get back to your work inside. We will put some pictures of today's recording on our Facebook page and you can also find us on Twitter - just search for Plant Earth Online. I'm Sue Nelson and that's the Planet Earth podcast from the Natural Environment Research Council from the top of London's BT Tower.