Cleaner City Air

We could have inadvertently stalled the greenhouse effect by historically including lead in petrol, a European and US team of scientists have concluded.

Writing in the current edition of Nature Geosciences, Ulrike Lohmann and her colleagues show that lead is one of the most potent water droplet-forming agents in the atmosphere.

Clouds form when rising warm wet air expands sufficiently to cool, allowing water molecules to coalesce.  At very low temperatures they can do this spontaneously but usually this occurs at much higher temperatures because the water molecules begin to cluster around particles of dust, pollen and even dandruff and bacteria.  These particles are collectively known as nucleation sites, and lead is the king.

The team made the discovery by sampling clouds collected in Switzerland and also by recreating clouds in the laboratory using ambient air samples.  When they fed their cloud samples into an analyser they found that the majority of the water droplets were associated with lead particles.  Presumably the chemistry of lead makes it an ideal rain-maker, but the implication of the research is that by choosing to lubricate the valves of engines by adding lead to petrol we may have made a significant different to global weather and global warming.

The lead particles, say the scientists, could have triggered increased cloud formation by boosting the effectiveness of nucleating particles in the air.  And because clouds reflect heat back out into space, this could have kept the Earth artifically cool despite rising CO₂ levels. The effect, say the researchers, could have been sufficient to send back out to space nearly 1W per square metre that would otherwise have hit the ground and warmed the Earth.  But now that we've eschewed lead in favour of a healthier atmosphere we may be about to reap the costs of the CO₂ seeds we've sown in the past...

Chris Smith -  Well also this week, worrying news about what is going on in Mexico.  We have seen the emergence of a former flu H1N1 but it is not the former flu H1N1 that we normally see seasonally in humans.  This form seems to be a swine, a pig form of the virus.  So far there have been a thousand reported cases and maybe as many as 50 deaths and it doesn't just seem to be confined to Mexico because cases have also now been reported in a number of US states, including the adjacent California, also Kansas now and also maybe even New York. 

So we are looking to see exactly what's going on and joining us is from Cambridge University, internationally renowned flu researcher Paul Digard, who is going to hopefully shed some light on this.

Paul Digard -   Good evening. 

Chris Smith -   Welcome to the Naked Scientists.  First of all, can you just explain for us actually what is swine flu, because we got our heads around bird flu as a risk, how does it compare, what is it? 

Paul Digard -   Well swine flu is influenza A, same as human flu and bird flu but it's a form that's adapted to infect pigs.  So history says that pigs had flu for at least last 100 years or so and when you look at the genetics of those strains, it's pretty clear that actually the viruses that infect pigs we have been swapping them backwards and forwards to in pigs and humans for quite a while. 

Chris Smith -   So in the same way that birds have their strain of flu which occasionally jumps into us, pigs have their strain of flu which occasionally jumps into us and vice versa.  It is a giant sort of genetic melting pot and on this occasion this strain we are seeing in Mexico is a pig virus that has jumped out of the pigs and into the local population? 

Paul Digard -   Probably, the virus that's been found in people of Mexico and in the US genetically has some characteristics of swine flu but that's not the same as known that has come directly out of pigs into people, we don't really know where it's come from yet. 

Chris Smith -   So speculating for a minute, just talking about the mechanisms as to how it could have arrived, how could it have got out of the pig and enter a person in terms of to arrive at this sort of genetic situation we see with this virus now? 

Paul Digard -   Well, it's speculation because I don't know, I don't know if anybody knows what has actually happened in Mexico but the usual route is as people work in the pig industry, the pork industry, they have close contact with pigs.  That's the start of transmission from animal to man and vice versa. 

Chris Smith -   So someone who is a worker, goes to work and comes into contact with a pig, the pig gives that person a pig virus directly, what about the other way round if the person gives their human flu to the pig? 

Paul Digard -   Same situation in influenza in pigs is very similar clinically to human influenza, it's a respiratory disease.  The pigs have respiratory distress.  They run on temperature.  The virus is probably transmitted by most the same route, by aerosol perhaps fur mites, just general close contact will get the virus from one organism to another. 

Chris Smith -   So if a pig has got it's own form of flu at the same time as human form of flu then infects the pig, is it possible the pig got out like sort of mixing pot and you get out of that a hybrid virus which combines the worst bits of both? 

Paul Digard -   Yes, that's the theory.  Pigs have been viewed as a mixing vessel for quite a while partly because we know that we can swap viruses backwards and forwards between pigs but even worse in the ways that pigs are also susceptible to quite a few strains of avian flu but when you look at the genetics of the viruses that you find in pigs it is pretty obvious that not only they are swapping genes between swine and human flu but they are also mixing an avian genes as well, avian virus genes. 

Chris Smith -   So is that why we should be more worried about a form of the virus that's come from a pig than just a normal human flu then? 

Paul Digard -   What makes the current swine flu more dangerous is probably that it's antigenically novel for the human population. 

Chris Smith -   Meaning it looks total differently, we have never seen anything like this. 

Paul Digard -   So you and I and probably most people have heard, we'll have already have H1N1 flu but they will have the human strength and at the moment it is not at all clear whether that gives you any protection from infection with this swine H1N1.

Chris Smith -   And the fact that you've got to catch flu the first time in some point in your life and most people don't die when they catch the flu, an appreciable number do but most don't, luckily, so why should this one be worse then?  What's giving it the edge? 

Paul Digard -   Well we don't know that it is worse and what we know so far is there's perhaps 60 deaths or so but we don't know how many people have been infected so we don't know what the mortality rate is and it could be no more virulent than current human flu, it's just there's a large number of infections that haven't been noticed because they have not been severe enough to the persons that go to a doctor. 

Chris Smith -   And based on what we know about the flu historically and the history has a habit of repeating itself we have had a number of pandemics over the years and most famous that we have got defined is the 1918 Spanish flu, estimated 20 to 40 million people died with that, how does this event fit with what we know about those previous pandemics? 

Paul Digard -   First of all, we don't know that this is going to be the next pandemic.  I mean there's a real chance it could be but we don't know.  It could just burn out, it could go nowhere, obviously that's what you'd hope.  If it does turn pandemic then it's different to the 57 and 68, it would be different from 57 and 68 pandemics because it was those were hybrid viruses between an avian strain and a human strain.  Genetically I don't think we can say that we have ever seen a pandemic starting from a pig virus before.  The 1918 virus, we don't really know for sure where it came from, probably avian but it's hard to say because we don't know what the virus before was.

Chris Smith -   But is there any reason why the next pandemic couldn't start with a pig? 

Paul Digard -   Oh no, no, in this I think there's a reasonable chance that in a year's time we'll look back and think yes, this was the start of the 2009-2010 pandemic. 

Chris Smith -   Lets hope not, thank you very much Paul.  That was Paul Digard who is a flu virologist at Cambridge University.

Chris Smith -  Now Professor Rod Jones who is at Cambridge University, has been working with Cambridge Council to find a way to fill in these gaps and he has been developing cheap mobile environmental monitors to really show how much pollution each person could be exposed to.  

Rod Jones -   Well the big issue that we are really looking at is that we know that air quality can impact on human health on the one hand and actually on the radiative properties of the atmosphere and the bigger picture still I guess, is that we know that as we look into our future climate, we are likely to see changes in air quality.  

So what we are looking at is trying to understand some of the basic principles associated with what controls air quality and ultimately I guess how we might take steps to try and mitigate changes in the future.  

Chris Smith -   Air quality can be considered in two ways so there's the air quality on the scale of whole planet and then there's air quality just around town, so are you looking at everything or you're just looking at one small component there?  

Rod Jones -   Well so our work actually looks at the global issues but this particular project is much more focused on local air quality.  So it's the kind of air that we breathe in cities and in urban environments.  

Chris Smith -   And when a person takes a walk down the road in the average city, what sorts of things they are being exposed to?  

Rod Jones -   Well a range of gases, things like nitrogen oxides, ozone of course, particulates and the main gases which I think are causing people concern.  

Chris Smith -   So how are you going to start with them?  

Rod Jones -   Well of course that probably is being studied at some level but a lot of the equipment that's needed to study, it is big, expensive and complex to run and so you can only locate measurements of that kind in rather sparse network and so what we are trying to do is to look on a much smaller scale, on the meters and more than that we are trying to introduce sensors which we can carry around in our pockets to monitor how air quality is changing and how the air we breathe is changing actually as we walk the streets.  

Chris Smith -   Because that's going to be a much more realistic measure, isn't it, because if you just sample one area, if the traffic isn't in that area or the wind's blowing the other way you are going to miss a lot of stuff, people don't stay on one place, they move around.  

Rod Jones -   That's right, and there's a certain amount of evidence that even which side of the street you are on when determining to some extent the exposure to pollutants that you are going to have.  

Chris Smith -   So what's the strategy?  What have you got to do this with?  

Rod Jones -   Well, nobody has adapted really.  Our sensors which are actually used for monitoring of dangerous gases and they are very small sensors in themselves so they are very amenable to being put into very small packages and so we've basically got a handheld device which weighs perhaps 200 gms which actually has on board GPS which we are all used to using in our cars for the location and in fact the guts of a mobile phone which is turned GPRS which allows us to transmit the data from these little boxes to a central computer in real time.  

So in fact what we can do is to give people who are involved with the projects, these sensors to carry in their pockets and on to the streets and we can actually map the pollution that they are being exposed to and in fact others around them are being exposed to, in real time.  

Chris Smith -   And how do you then put all that data together?  How does the system actually work to compile real time data and link it geography?  

Rod Jones -   Well of course the GPS tells you where you are and we can then map the pollutants that we saw the pollutant levels that we see on to even simple things like Google Earth and so that you can see precisely where the high levels or low levels of pollutants are.  Of course it's never that simple because as you said a moment ago, standing on one point the pollution varies quite widely but we are able to, at least to some level to pick up that as well.  

Chris Smith -   How are you actually getting data yet or you're just at the stage where you have got prototypes of the devices now it's ready to go out in teams of people to see what the pollution looks like?  

Rod Jones -   That stage that we are at is that we actually have a pretty advanced prototype sensors which include, as I said, the GPS, GPRS or the communications on location and we have them in sufficient numbers that we can actually pretty much inundate a city.  Where we are not quite there yet is in the sophisticated analysis software that you need both to analyse the data from a scientific perspective and to produce something which somebody can log on to the web and actually see in a web page what the pollution for a particular time of day or what they might be expected to be exposed to if they lived in a particular part of a city, is, and we are working very rapidly on that.  So we are hoping to put together the whole package but it's not quite the finished article yet.  

Chris Smith -   How are you going to use it?  Is this going to be giving pedestrian these devices?  Is it going to be cars these devices because obviously they are going to see different levels of pollution and what sort of resolution you are able to get because can you literally see someone walking on a pavement versus someone in the car or on the road?  

Rod Jones -   Some of the sensors are certainly capable of detecting those, that the differences between being in the centre of the road and being on the pavement but I think really what we are aiming for here is to produce a network of sensors which solve, which will be static in fact but any kind of platform, moving platform as well as lamp post, for example, would be used to provide us with a very wide range of data for this very complicated environment and where you can envisage somebody walking down the street with their mobile phone actually using WiFi or the Internet to pick up a map which gives you real time pollution.  

Chris Smith -   And that was going to be where I was going to go next which is to ask you well how is this going to guide either re-planning of towns and cities and traffic flow or how humans behave?  

Rod Jones -   Well there are ranges of activities which could be influenced by this.  If you have a sophisticated network of air quality measurements then you can actually use that to begin to understand how that links into the detailed traffic flow and ultimately you could think about controlling traffic flow to minimize the hotspots, the pollution hotspots.  

On another level you could actually use it to begin to map out if you like the lowest pollution path between your place of work and your house and so somebody in the morning can get up and look at the web and decide which is the preferred cycling route which is going to give them the least level of exposure to pollution, that's a dream for the future but it's not that far in the future.  

Chris Smith -   And do you think you'll see yourself one day in the position where you will be able to go up to the developer who is about to put in a new housing state and you would say 'Don't build your roads like that because we know that will create a greater pollution problem than if you plan like this'?  

Rod Jones -   Well I think we, in a sense, have a responsibility to try and answer those kinds of questions, how clear cut an answer you can get for some of the questions that you have just asked, I am not really sure yet but we are to be able to derive a general picture of how to, for example, build a housing estate in a green fashion.  

Chris Smith -   Indeed, and also get to work with the least inhaled aerosol pollutants, it sounds good news to me.  That was professor Rod Jones, he is at Cambridge University's Chemistry Department who was explaining to me there how his handheld devices could make sure that new developments are brought in locations that would do the least environmental damage and also let people plan their healthiest commutes or even the cleanest walk to the shops.

Chris Smith -   So we have heard about the developments in monitoring pollution in enclosed urban environments but other systems also contribute to the quality of air across the country and Dr. Stephen Ashworth is in the University of East Anglia in Norfolk where he studies the gases that come from marine systems to find out how they contribute to the chemistry in the air around us and that means on the scope of the whole planet.  

Stephen, hello, welcome to the Naked Scientists.  

Stephen Ashworth -   Hello.  

Chris Smith -   So what are the big questions you are trying to answer?  

Stephen Ashworth -   Well, this work came out of a campaign that goes ahead of Mayshead.  We heard in a piece just a moment ago about the natural background levels and one thing that's very important for us atmospheric scientists to know is what those natural background levels are.  Now one place this is done is at Mayshead in island and the idea behind that is the prevailing wind is from the Atlantic so there's very little pollution.  So on days when it's blowing from the west we can get a very good idea of what natural background levels of various components of the atmosphere are.  

But one thing that came out of one of these campaigns was that there were very high levels of particles detected, these aerosols that we have been talking about and having detected these particles the question was what goes to make them up, and it turns out that these particles have a lot of iodine in them and the iodine was traced to the seaweed on the foreshore at Mayshead.

Now the question is then is this a local phenomenon or does it affect the whole globe?  

Chris Smith -   So what you are saying is that the iodine which is coming presumably from the sea, could be getting into the atmosphere in clouds and therefore triggering things like cloud formation and therefore influencing rainfall?  

Stephen Ashworth -   Exactly, certainly the seaweeds give off a lot of iodine in compounds and that iodine then gets processed by the atmosphere and turns up in these aerosol particles and they are just the sort of surfaces you were talking about right at the beginning that would enable water to condense and form clouds.  

Chris Smith -   How does the iodine get out of the seaweed and into the atmosphere? 

Stephen Ashworth -   Well, it seems that this is mechanism against stress.  If the seaweed feels stressed it releases these compounds and one of the things that stresses seaweed is the tide going out so they tend to get dry and release compounds containing iodine.  

Chris Smith -   So that would then be blown up on the pervading wind into the atmosphere where it would then have downstream, excuse the water pun, effects on the weather.  

Stephen Ashworth -   Yes, exactly.  The sun shines on these compounds, the light, it's the interaction with the light of the sun that causes the iodine to be broken off these compounds.  It then turns out and reacts with ozone in the atmosphere to produce iodine oxides and there what go on to make up these, the particles.  

Chris Smith -   So how are you trying to understand more about this iodine and to understand more about the chemistry as to how it gets into the atmosphere and how much width there is?  

Stephen Ashworth -   Well the idea here is that we can measure in the atmosphere what's there.  We want to answer the question how was it produced and what's it going on to make at a later date with interaction with other chemicals in the air, with sunlight and whatever.  So we need to take things back to the laboratory and make these compounds under as controlled conditions as possible and analyse how fast they react, what they react with and what they turn into once they have reacted.  

Chris Smith -   And how are you doing that?  

Stephen Ashworth -   Well we can mimic this process by producing ozone in the sample cell and feeding in some iodine containing compounds.  We can also mimic sunlight in the laboratory fairly well and we find that we make lots of particles.  Another experiment that we have done is to actually try and break down the production of the particles into a series of steps and so that we build up the iodine oxides one step at a time.  

We find to do this, these compounds don't absorb very much light.  This is how we measure how much we have got and how fast it is reacting.  We use a laser to see how much light is absorbed.  

Chris Smith -   All right, so you know the different chemicals absorb laser light at different wavelength so if you shine a laser beam of the right wavelength through it, the amount of laser light that get soaked up must be proportional to how much of the chemical is there.  

Stephen Ashworth -   That's exactly right but because we need a lot of chemical in this case to actually see the change in the laser light and we have to do a little trick by trapping the laser light between two mirrors and that makes it bounce up and down through our sample lots of times, and if we are lucky with the right combination of circumstances we can get effective lengths.  So it makes it look as though the sample maybe 10 kms long.  

Chris Smith -   Has anyone actually done this in terms of really shining a laser beam through 10 kms of atmosphere rather than bouncing it on a light path, 10 kms long between two mirrors like this?  

Stephen Ashworth -   There are experiments which do that, you can shine a laser beam 90 kms up into the atmosphere and get a signal back in an experiment called LIDAR but it's a slightly different principle that's involved there.  

Chris Smith -   But do the results agree?  So you think you've got a good model with your mirror bouncing system to accurately predict this important aspect of atmospheric chemistry?  

Stephen Ashworth -   Okay, I misled you a bit there, the LIDAR results aren't actually used on the iodine chemistry but we believe through modeling - again we have heard earlier in the program about the various modeling that can be done - by modeling the systems using the results from the kinetics that we measure and how fast these reactions go and what's produced, we can be confident that we have a fairly good understanding of this system.  

Chris Smith -   Genius, thank you very much Stephen.  

Stephen Ashworth -   My pleasure.  

Chris Smith -   That was Dr. Stephen Ashworth who is from UEA, University of East Anglia working on ways to detect the chemicals that are important to climate and the earth's atmosphere.

Chris Smith - Well I think that Paul has a point which is that there's no such thing as a free lunch. If you are suing energy it's got to come from somewhere but the benefit in electric car offers is that it doesn't produce pollution once it's working as an electric car, obviously the pollution is all in one place, the power station, and that means that mitigating strategies to recover the waste from the power station, the CO2, the particles etc. can be done locally where the power station is and probably more effectively than fitting scrubbers and things which will be less efficient to a car and also individual cars are all going to be inherently less efficient than one giant power station.

So it's the sum of lots of little inefficiencies adding up to a bigger inefficiency, the one big inefficiency - the power station. So that's why we think electric cars are beneficial. They also are much better in traffic because stopping and starting burns enormous amounts of fuel waste, enormous amounts of energy. Electric motors are absolutely perfect for that kind of thing because they don't waste energy when they're not actually moving.