London’s Air: The 70th Anniversary of the Great London Smog

- First thing I have to say is, what a difference 70 years makes. In front of me I have my phone, and on my phone I have the air pollution forecast for London today and tomorrow, it says, low, okay? On Friday, the 5th of December, that wasn't the case, it was bitingly cold. There was a stable air mass of damp air hanging over London with no wind, and so, every chimney from every household that was burning coal, every factory, every power station was emitting their smoke into effectively a stable box of air. And from today, 70 years ago, the city began to be covered in a blanket of toxic yellow smog. Now, today's the 70th anniversary, it's timely. It was an accident that this happened in terms of my talks, but it's not really when you consider that 12,000 people died, that a hundred thousand people were ill as a consequence of the London Smog, really much to celebrate in terms of an anniversary. So what I intend to do today is really to memorialize the event on the day that London choked and coughed and sputtered beneath this pollutant blanket, and really want to focus on is the 12,000 individuals who lost their lives across those five days. Well, actually more than those five days as we will see. But also the 26 to 38,000 people who will die earlier than they should do this year because of the air pollution we currently experience within the United Kingdom. Now, air pollution did not start in December, 1952. London had had air pollution ever since it began to grow as a city through the 18th and 19th century as the population grew, as the city became more industrialized, we were familiar with the classic pea soupers, they're in Dickens, they're in Conan Doyle, we are familiar with them, they're almost romanticized. In fact, the artists, our historic artists, here we have Monet, managed to capture air pollution, it looks kind of rather beautiful, doesn't it? Until you realize that that wonderful quality of light that Monet came to London to capture was a combination of the smog, the smoke, and those fantastic sunsets caused by the scattering of light by particles held suspended in the sky. So Monet captured it, Turner wasn't a bit shabby either, celebrating smoke, capturing these amazing sunsets over the Thames. But this is historic pollution. But at the time, people didn't really dwell too much on it. In fact, at the time, people actually thought of smoke almost in a beneficial faction, they've almost thought of it as being curative, something which protected you against the infectious air, the miasma within the city. And whenever people did refer to the smog, the smoke over London, the pollution in the context of health, it was to do with light, the smog preventing enough sunlight to make adequate vitamin D leading to Rickets, potentially exacerbating people who had tuberculosis within the city. So it was there, but it really wasn't appreciated as being a significant contributor towards the health burden of London. Now, so we had pollution in London, but let's not pretend that the story of air pollution and health begins in our city. There are a number of highly significant events which should almost have been viewed as an early warning that something was awry. I'm afraid this picture isn't particularly sharp, it's the best picture I can get of the Muse Valley in Belgium taken in 1930, it's December the first to the fifth, again, cold, stable air, no wind, an industrial valley with manufacturers, which over this period of time resulted in the buildup of pollution in the valley. Now, what's significant about this event is thousands of people fell ill with a respiratory complaints. So there are records of the respiratory complaints they had, and something in the order of 63 people died as a consequence of this air pollution event. Now, again, even in the Muse Valley, this was not new, they'd had a similar episode in 1911, which was characterized by the fact that the smoke built up in the valley and cattle died. So as this event was beginning in the 1930s, the farmers actually led their cattle out of the valley so that they wouldn't die, because cattle seemed to be particularly vulnerable to the respiratory effects of poor air quality. Now, the other thing I wanted to highlight here was, there's a memorial to the 68 individuals who died as a consequence of the Muse Valley Air pollution episode, and we'll drill a little bit more on that as we go on. But the other thing which came out of this event was a report which stated, just imagine what would happen if something like this happened in a major city such as London? We would estimate something in the order of 3,200 deaths. So let's hold on to two things there, that number and the cows, it will all (indistinct) in the end. This, I think is very tangible. These are autopsy samples of the lung taken from an individual who died during the Muse Valley smog episode. And what we have over here, I'm old school, so I'm going to use a pencil, not a laser pointer, yes? This is the alveolis of the lung, your gas exchange region. And what you can see is this layer should be really thin, but it's actually quite thick 'cause it's congested, and the actual airway sack is full of liquid. And that little sort of granular appearance of it are inflammatory infiltrates. So what you have here is what I would call a diffused alveola damage pattern. This lung is inflamed and it's leaking the constituents from the blood plasma into the airways, congesting the airways. And this little figure here is if you are conducting airways, well, what I tell you is this should have lovely cells with lovely cilia, yes? At the top you can see they're all gone, yes? So you can see the actual pathological consequences of the air pollution this individual was breathing which resulted in their respiratory failure all that time ago. The other significant event happened 18 years later, and this is in the United States in Donora, about 30 kilometers south of Pittsburgh, a steel and zinc manufacturing area. And again, there's a common pattern, emissions from factories, a period of cold, stable air with low winds. Again, this resulted in a buildup of air pollution in the valley that resulted in really lots of people falling ill, again, 18 to 20 people, the number's contested, dying of this event in a valley of only, and a population of only 18,000 individuals. Again, just out of interest, those 18 to 20 individuals have a memorial, which also marks the fact that this event was absolutely seminal in the establishment of federal legislation in the United States to attempt to clean the air. Now, let's bring this home. This figure is probably one of the most famous figures in air pollution research. And what we have here, I'm trying to work out what the best place to stand is, and I've concluded there is no best place to stand, so I'll do my best, okay? What we are looking at here in these sort of red triangles is the concentration of something referred to as black smoke. Now, black smoke is a measurement of the particulate, the soot-like particulate within the air. And here we have the first, the second, the third, the fourth of December, and now we hit the 5th of December, our anniversary today, and we can see this black smoke concentration suddenly shoots up, continues to go up, it peaks around the seventh and the eighth, and it's peaking if you go across here at 1.6 milligrams per meter cubed. This is astronomically high and that's an average, yes? I've seen figures from certain areas in lab where it goes up to over 2.5 milligrams per meter cubed on a daily basis. Then, on around the ninth and the tenth, the wind begins to pick up in London and the pollution begins to dissipate, and we begin to go back down to these sort of background levels. Now the other pollutant on here is represented in these little blue triangles, and this is sulfur dioxide. And this is really important because what you have here is an episode driven by this stable air mass but there's other stuff at play, and some of that stuff is political, and some of it is economic, yes? So why do we have this big peak of sulfur dioxide? Because the coal which was being burnt in London was of low quality, in fact, some of the lowest quality. There was a product called nutty slack, which you could have in your fireplace, yes, which didn't actually come off your rations, so therefore it was a good way of heating your house. Why were we burning low grade coal in the United Kingdom when we produced high grade coal? Because we were bankrupt after the second World War, because we had our war debts to pay, and so, the high quality coal was being exported overseas to help with our balance of trade deficit. In a sense, we had a bit of a fuel crisis occurring at this time, issues of fuel security. Now all of that's just the episode, yes. I almost just said the killer statistic here, but it is the killer statistic is the number of daily deaths in these green squares. Now here, we have, like, a just background daily death in the winter. People die more often in the winter, there's influenza, it's cold, you expect to (indistinct) what we would rather cold heartedly call harvesting, yes? But as the pollution begins to go up, you can see the daily death rate increases, and you can see that we have this big excess death occurring over that episode. Now, that little peak between the fifth and the tenth corresponds to 4,000 roughly excess deaths within London. But I told you it was 12,000, and the reason it's 12,000 is because if you look over here, you can see after the pollution has returned back to normal, this continues to track down, but it clearly hasn't got back to the levels before the event, which means that the air pollution event, again, using indelicate language, was killing people quickly, but also killing them a bit more slowly as well. And if you integrate not only that peak, but this lag, you get in the order of 12,000 excess deaths. That's astronomically high. And this is really the first point in history where you have an event like this occurring in a major city with statistics on health which allow you to make that association. That's why this event is so important. And I have to show you pictures, and I have to try to make it visceral, yes? And I tried to get pictures most closest to here as I possibly could, but when I was putting this together, I got an email from Brian Cummins who was a 22 year old man living in London, going to university at this time, and we just chatted about what it was actually like, yes. And that really helped me sort of just get this idea of him. He was able to walk along the streets, he was young, he didn't have any ill effects, but he could hear people coughing as he was walking along, some people were suffering clearly much more than other people, cinemas had to close because of the infiltration of the smog from outside into the cinemas. And if you consider that cinemas in those days allowed you to smoke and it was already pretty difficult to see the screen, yes, you can imagine how bad that was. Football matches had to be canceled because you couldn't see the penalty spot, public buses had to be led through the streets by flares. That 1.6 milligram meter cubed of black smoke in places resulted in visibility of about one meter, yes? So it was incredibly tangible. Now, the other thing, and I hadn't thought about this until I spoke to Brian, was of course I just was sitting there going,"Well, you can go home." Can you? Leaky, old Victorian houses, porous houses, with the pollution outside infiltrating inside, he said,"You know, in the university you could walk down the corridors but you couldn't see in the corridors because the smoke had come inside." And of course most of these houses were burning coal in open fireplaces to keep warm. So actually everywhere, there was nowhere to escape in reality during this period of time. Now when I look at things like this, they look as though they're captured in the past because they're in black and white, yes? And I was listening to an old BBC recording and they talked absolutely about this yellow haze in the air, and I've never seen it. I've talked about this many times and I just, I'll go through these, this is some of the headlines, yes? The headlines are fascinating, they're fascinating because people are dying, yes? The undertakers are really worked off their feet, the mortuaries and the hospitals are full, and what do the newspapers focus on? They focus on accidents and the cost to the UK economy and strange events and the fact that under these conditions when nobody can see, you know, the FIPs are making, hey, nothing on health really was coming out. In fact, there was a story, returning back to cows, that in the beginning of the episode there was a livestock market at Spitalfields, a show actually. And actually I think something in the order of 13 prize bulls dropped down dead, but not the sheep or the pigs, and I've still got to work out why that is. That's bugging me, but there must be a reason for it. This is what I wanted to get you to. These are color photographs of the London Smog. I found them just going online produced by a colorist called Stuart Humphreys an a site called BabelColor. And it captures that yellow orange haze within the air, which reflects the sulfur dioxide within that mixture in addition to those fine particles. And I loved it."London coughed and crawled almost almost to a standstill in a murky yellow gloom." So, who died and what did they die off? Let's get straight to the key issues, yes? Now, I think there's this kind of narrative, which is, the people who died during the smog were probably really quite elderly and had very, very severe chronic diseases. Again, it, you know, just pushed them over the edge. But the data doesn't quite suggest that. This is a really simple piece of data, it's not the whole numbers of the event, it's just looking at a couple of administrative areas, death rates before the episode, death rates after the episode, and then there's a ratio. And it's stratified it by age, greater than 75, 65 to 70, 45 to 64, all the way down to newborns less than one month. And if you look at that, well, yes, the old, as they're defined, died as long as you are happy to accept the old means anybody over the age of 45 years, and increasingly, I'm not willing to accept that. And the other group who never get mentioned at all are the very young, the newborns, children under a year. So these are lessons we're beginning to take from that episode 70 years ago, which we can think about today. And what did they die of? Because I get the idea, we have this, you know, nothing really, we'd learn things very slowly. This is a breakdown of what people died from, and it was delivered to the London County Council on the 3 February, 1953. It didn't take them very long,'cause at this time we have the fledgling National Health Service, we were collecting health statistics properly. So, deaths due to bronchitis, tenfold increase, influenza, seven. Is that the smog, is that an epidemic happening in the background? Do you have to unpick that? Tuberculosis, 4.5 times, other respiratory diseases, predominantly asthma, 6 times, disorders of the heart and circulatory system, we have threefold increase. And again, I think this is interesting'cause people often think that we only knew about air pollution in the air maybe from the mid nineties, but there's actually some data all the way back here in 1952 suggesting that we have this increased rate of cardiovascular deaths. Now, again, some pathology, yes? Let's make this real. Because actually, one of the problem with air pollution is that a lot of it are dry statistics and numbers, yes, and we talk about death, and actually death is a really crude statistic, isn't it? Because the mortality rate of the human race is a hundred percent, so it's pretty meaningless. What we are really talking about when we talk about those deaths are people dying a variable time earlier than they should do, and behind that, lots of ill health. But this is a cross section of the surface for cut lumen from somebody, again, who died of bronchitis during the London Smog. And it's looked using an EM technique which allows metallic, metal rich particles to shine out. So each time you see those little shining things, you're looking at a metal rich particle. And one of the things we often think about the London Smog is there are these big soot particles in the air, yes? Which aren't like pollution we have today because that's really different, but this is a scanning electron micrograph of those particles in that tissue. And actually when you look at it, this bar here is 300 nanometers and you can actually see, rather than being big particles, they're actually kind of like a conglomerations of smaller particles. If you're into histopathology, this means something, to most people, it just looks like a pink blob. So I'm going to take you through the pink blob. Here, you're looking at the surface of the airway, these little black bits are macrophages. These are kind of like the janitorial cells on the surface of your airway which go around collecting debris eliminating bacteria. If they take up black carbon, they turn black, they accumulate it. And you can see underneath the surface of the airway, these big accumulations of carbon laden macrophages, and around them, all these sort of, like, pink cells are inflammatory cells. So again we can see the particles are in the lung and they're associated with actually inflammation. And if we look inside the macrophages which have that material, again, we can see that they're relatively small particles, and they're relatively metal rich, and you can go further than that and you can work out what metals they are, iron, led, zinc, tin, antimony So we can begin to unpack this, we can begin to see what's going on within the actual issues of these individuals. So, 12,000 people have died, certainly 4,000 of those deaths were known about relatively quickly, and what they died of was known about relatively quickly. So you can imagine any government at the day would be catalyzed to take action, okay? And this is the first lessons we learned from the past moment, yes? Because that's not the case, they knew this was coming. These are statements made by Harold Macmillan before he was prime minister when he was actually in housing and the environment department. And people were already discussing the air pollution problem in London before the smog. And he makes, I think, which are very kind of like, they make absolute sense from a political perspective."I suggest we form a committee. We can't do very much but we can seem to be busy, and that's half the battle nowadays." Yes?(audience laughing) But more important than that, this is the classic kick in the can down the road philosophy, but this is the really important one. In tackling air quality and the challenges that causes, an enormous number of broad economic considerations have to be taken into account. And within that sort of very large bucket of economic considerations, there's even the fact that at the time the government didn't really think there was an appetite within the population to give up their fireplaces, yes, to give up their fires. They were worried about whether the population would go on that journey of behavior change to improve the air quality in the city. Not surprisingly, they formed a committee, yes? The Beaver Committee. And the Beaver Committee was led by Sir Hugh Beaver, and he reported back, I'll get the date right here, on the 25th of November, 1954 with a series of recommendations based on the London Smog and the events. And they're really quite interesting, in fact they were defined as being radical changes, which is any change at all usually within a political framework. He said we should mandate towards smokeless fuels, especially within cities with the creation of smoke control areas. They said we needed a plan, a national policy, a five year horizon with sort of little markers to see how we were progressing on those plans. They said we needed to think about the power stations and energy generation and how we made energy and where the energy generation occurred, because at that time, it was largely occurring in the center of our cities. And they also argued that we needed, and they always argue this and I would never complain about this being a scientist, they said we needed more research. Don't we always just need a bit more research? I think that's very, very important. Now again, that's proposed, it's handed to the government, government again don't do very much, this is still not near the top of their post-war priorities, yes? But it's taken up by a conservative back venture known as, again, I always get his name wrong'cause I always think, he's actually quoted in a Monty Python sketch, so I always get really confused, but Jerrod Navarro, yes? Now he's a pretty complicated figure, yes? I think it would be fair to say that if he even opened his mouth today, he would be counseled absolutely immediately. However, he championed these amendments and put forward as a sort of private member's bill, the Clean Air Act or the beginning of the Clean Air Act. And actually, despite the many things he said and the strangeness of his, you know, complex personality, he was also on the Coroner's Act, he was also on the cigarette legislation, you know, banning cigarettes. I mean, he did a lot of really, really good stuff. But still it is a private member's bill. And it was only subsequently taken up by government, the conservative government of the day and forced through. And so that's when we get to the landmark piece of legislation. And this is a landmark piece of legislation'cause it really is the first time a government is really doing something about air pollution. And here we have the 1956 Clean Air Act. Now, this sort of made big restrictions on the burning of solid fuels in cities, but it also gave subsidies to people to transition away from old fuel use to new fuel use. And to be frank, they were quite lucky, yes? That this all happened at about the same time that natural gas was beginning to come online downstream, yes? So there was an opportunity which kind of smoothed it out a bit, which it would've been a bit challenging if that hadn't happened. And as a consequence of that, we can draw a graph like this. Here we have milligrams per cubic meter of sulfur dioxide, smoke, and I'll get to nitrogen dioxide in the center, here we have the mid fifties. And we can see basically these two pollutants we were concerned about in the London Smog are tracking ever downward. That doesn't mean 1952 was the last smog, there were smog episodes in '56, '57, '62, '75 all the way up to 1991, yes? But nevertheless, you could see it, the air pollution was going down. Now one of the things which happened in 1955 is that, because of the requirement for more research, they formed the MRC Air Pollution Unit, yes? And that of course, ran all the way out to 1978 when the problem seemed to have gone and they closed it down. Problem solved, air pollution has been solved interestingly through regulation and policies, yeah? Not by anything particularly innovative, just by laws. Now, had the problem gone away? I'm jumping from the London to the United States now. Because everything changes in air pollution research with this paper published in 1993, and it's a deceptively simple paper.'Cause this is the point we stop worrying so much about episodes of air pollution, ginormous pollution events. We begin to get much more concerned about what it is like to live somewhere, which is slightly more polluted than somewhere else over a long period of time. It's also one of those wonderful papers. It's one of the few papers that undergraduate students can always quote in an exam because it's called the Six Cities Study because it's about six cities, so they're automatically in through the door. We have six cities, Steubenville, St. Louis Harriman, Watertown, Topeka and Portage. And in these cities, they're looking at the probability of survival over a 12 to 14 year period in relation to the average pollutant concentrations in those cities over that period of time. And they're measuring total particles, that's a bit like black smoke, fine particles, we now call that PM2.5, those are the particles which are meant to go deep into your lung, and then they have sulfate particles which are part of PM2.5. And you can see there's a sort of like a spectrum from high through to low. Okay, so what has happened? So here we have your probability of surviving in the cities over time, and this is quite straightforward. Because what it tells you is, if you live in the really polluted places, your probability of surviving over this period of time is considerably less than if you live in clean cities. So there's something about the dirty cities which is causing you to die earlier. But of course there are millions of reasons why that could be the case. These are working class, blue collar steel towns, yes? Smoking, low education, poorer diets, you can think of a million reasons. But what's really elegant about this paper is that they develop methods to de-trend out all of those other, what we might think of as confounders. And at the end of it, they end up with the second, with the London Smog probably in joint first place, important figure in air pollution research. And how simple is the figure? I'm just about to show you. Look in the middle panel. This is the concentration of fine particles, this is your increased chance of dying prematurely using the death rate at Portage as your reference. So Portage is one, and then you are going,"Okay, this is the increment in each of those places" after adjusting for socioeconomic situation, smoking, work, a whole host of things." And this P, is Portage, S is Steubenville, these are the main positions. This is a straight line, this never happens, yes, in science. Science is a mess normally, yes? You don't get a beautiful straight line. And you'll often hear people telling you about there's no dose threshold, did it go? It is a very linear relationship. Look at this, from 30 to 10 micrograms per meter cubed, pause, we were talking in the London Smog of 1.5 milligrams per meter cubed, and now I'm telling you that concentrations between 10 to 30 micrograms are having an effect over the long term on your chances of surviving. Now, that's remarkable, but because now you can look into this, you can see that people are dying of COPD, emphysema, bronchitis, so that's the umbrella term, pneumonia and cardiovascular disease. And actually the cardiovascular disease is probably the most statistically significant finding, not because it's the biggest effect, but because the error bars are quite small on it, so there's greater certainty on it. So air pollution at historically low levels are having a profound effect. And this study has been replicated across the United States, across 150 metropolitan sites, across Europe and China, it's one of the most robust findings I think science has generated in the last 50 years. Low levels of air pollution of particles that are associated with excess death through cardiopulmonary, which is me hedging my bets causes. Now, if I took that association and then I estimated PM2.5 exposures for the entire global population, sounds massively ambitious but you can do it if you accept some uncertainties. It's now estimated that each year, globally, roughly between four and four and a half million people die prematurely as a consequence of fine particular matter, fine. What do they die of? Well, more or less the things I've said before, but I can add a few more into here. I hadn't really focused on lung cancer and, actually there's a very strong association with stroke, yes? So that's another very, very strong association. But what I wanted to put here was this issue about death. If you're looking at death, you are looking really at a very blunt endpoint. Because beneath death are years, decades of ill health, disease exacerbation, doctor appointments, medication uses, and you are thinking about this in terms of a health economist, once you're dead, you are relatively, you are saving, but while you are alive and costly and in the health system, that costs money. And then the other thing I wanted to say is that the other danger of thinking about death isn't thinking about vulnerable people is you forget that air pollution affects us off, but that very often we don't know what it's doing to us. A bit like a teenager smoking a cigarette, it doesn't have any ill effects and doesn't realize that this one cigarette doesn't sort of magnify to the lifetime of exposure, which leads to disease. There's a lot of, if you like silent, subclinical harm being done to the system through the air we breathe over the long term. So where are we? Nasty soot 1940s and fifties coal burning, 1960s and eighties, everything seems to be getting better, there are some stories out there. Ozones a bit important in America, particularly in California, some concerns over lead and petrol, that's an entirely other talk, I'll have to do that one day. And then we move through to sort of like the eighties to the two thousands, and now we begin to see our new concerns. So now longer levels of pollution, but the focus has changed from burning coal or industry to traffic, and specifically within Europe because of our policies from the midnights onwards towards emissions from diesel vehicles. Why are we so obsessed with diesel emissions? It's because you can relate asthma exacerbations in children to how close they live to a road and the number of diesel vehicles it has on it very, very simply. There are lots of bits of data demonstrating that diesel exhaust seems to be particularly harmful. But you can go beyond that. So this is kind of a study that I was involved in and some of the studies I've done in which we actually demonstrate that diesel does bad stuff to you by taking usually a medical student,(audience laughs) putting them in a box, and then behind this wall, this is a Volvo bus engine, making diesel, diluting it in this tube, and then delivering it into that room. So this individual's being exposed to diesel exhaust. Levels are relatively high, yes, but they're doing this just once, yes, as opposed to living in a dirty city. It'd be the equivalent maybe of sitting in a London bus stop for, you know, eight hours a day or something if you were to do something so foolish. Why does this matter? Because after you've exposed them, you can do a bronchoscopy. And with the bronchoscopy, you can actually go into the lung and look at the inflammatory changes which are occurring in the lung and actually take little tissue biopsies from the lung to see what's going on. And yes, I have had this done to me, and it's fine. This is an individual, he's being exposed on two occasions separately, once to diesel exhaust, once to filtered air. And this is after filtered air, and this is the surface of the airway, these are the sort of epithelial cells, and they sit on something which we call the submucosa, it's kind of like the stuffing of the lung. And what we've done is we've stained them with an enzyme antibody for something called neutrophil elastase. It recognizes neutrophils, I think of neutrophils as being like the infantry of the immune system, yes? That's the easiest way of thinking about them. After air, not very many, after diesel, lots of neutrophils, puffy red tissue, very inflamed. Does the patient have any symptoms? None. Is he aware of discomfort? No. What's happening? There's just a smoldering inflammation in their airways just occurring in the background. Not significant on a day, magnify that by 10 or 20 years. This is just to show that when we do the actual stats on multiple people, it sort of hangs up, all of these individuals have this effect. And actually we've done lots of studies and we can show there's inflammation, we can show the lung function's impaired, we can show changes in the mediators on the lung, which make the lung more susceptible to infection, and in fact, you can show cardiovascular effects, changes in blood viscosity, heart function, arrhythmias, all of these things can be changed. Now, these are healthy individuals operating within a normal range, but they demonstrate that the air you breathe, the diesel in the air you brief, yes, has an actual adverse physiologic effect. But still, it's a Swedish medical student because there's not much to do in the winter, and so they're really good candidates. It's still not the real world, but my colleagues at Imperial did an incredibly elegant study with asthmatics this time in which they made use of London's very own diesel chamber or it used to be London's own diesel chamber, which was Oxford Street. At the time they did this study Oxford Street could only have diesel buses and taxis going backwards and forwards, yes? Tall buildings on both side, it's a diesel chamber, yeah, like it or loathe it. And they got their asthmatics to walk up and down Oxford Street for two hours, that's exposure number one, and then their control exposure is they sort of walked around the round pond, that sort of jumped from the round pond, but it should be around there, okay? So that's sort of an urban park background exposure. And then they just said,"I wonder what happens." Okay? So all you're looking at here is a change in a measurement of lung function, forced expiratory volume in one second. Yes, think of it as how twitchy your airways are if they're slightly irritated. And here we have the individuals, this is their walk period here, and they're walking along, this is the park, and the same individuals walking along Oxford Street. Bang, 5% reduction in FEV1, and that reduction is sustained out to 22 hours. Conclusion, their lungs don't like this very much, yes? Still no symptoms, no complaint, very, very mild, but you can see something is irritating the airway. Over here, they want to look at inflammation in the airways because they're asthmatics and they're quite (indistinct), they didn't do bronchoscopy they used a technique called induced sputum. It is charming, you breathe a nebulized hypertonic saline, it makes you gag and you cough up big balls of mucus, yes? And in those big balls of mucus, you can measure stuff. And what they measured was an enzyme called myeloperoxidase, which is released from neutrophils where neutrophils are particularly angry, yeah? And so what you can see is, this is the park, that's Oxford Street. So just the air animosity is having this background irritation, inflammatory effect. Okay, but what happens if you live somewhere like that all the time? That's really when it begins to get interesting. So what we have here is a picture. This is taken about 2011 looking out at Tower Hamlets in Hackney, and that's because I was doing a study at the time looking at children's lung development in the city. What did we find? We found that by the age of eight to nine years, a child growing up in Hackney and Tower Hamlets on average had lost somewhere between 100 and 120 mils of lung volume because of their exposures to traffic related pollution. Now, in an area of London, which was outside the legal limits of nitrogen dioxide and had been for very, very long period of time. But those effects are quite minor, they don't have to be minor. This is Ella Kissi-Debrah. She died of an asthma attack in February, 2013, 10th anniversary coming up shortly. When she died, she had very complicated asthma for a very, very long time. In her initial inquest, it was respiratory failure, but her mother then became interested in the fact that they lived near the South Circular Road in Lewisham and became aware of the literature on air pollution and risks of asthma. And then through interacting with the medical profession from expert evidence from Stephen Holgate, actually, they reopened the inquest. And in 2021, Ella became the first person in the United Kingdom to have her death certificate modified to illustrate that air pollution had actually contributed significantly to her death. I think this is incredibly sad, but actually all of those numbers I've given you before are a life, all of them are a face, all of them are a person, but somehow this makes it that much more concrete. These numbers reflect grief and suffering at the family level, at the community level in a way that people don't necessarily understand when they think purely of these numbers. And in our city today, these are all recent studies demonstrating increased visits to GPs for asthma related to air pollution and medication usage in our city today. There's increased evidence that air pollution is linked right now to increased rates of dementia within individuals living in the United Kingdom, with increased rates of mental health, with declines in cognitive ability. And all of this feels as though air pollution's associated with everything, but I generally just think air pollution just gives you system-wide problems, yes? How it manifests probably is related to your lifestyle susceptibilities and your underlying genetics. But air pollution isn't neutral, even at the levels we experience it today. It affects us across our entire life course, that's new. I wanted to say from cradle to grave, but actually it's before cradle to almost grave, yes, to be precise. Because air pollution is being associated with low birth weight at term in the United Kingdom, in London now. It has an effect, all the way through of these other issues. So all of that is rather depressing. I should have warned you that I have a bit of doctor death, sorry, I have to apologize, but I'm going to give you some hope. Here's some hope, where things are done which result in air pollution going down, things actually get better. This is the six cities study again, yes>? This bit is the bit they published originally, and then they went back because the U.S. Government put in regulations to reduce air pollution, and air pollution fell in the six cities. And as it fell, if we start here, these are the original data, Steubenville through to Portage, in each of the cities, when they went back, as air pollution fell, the probability of dying early fell. You reduce air pollution, you gain years of life back, but more importantly, years of healthy life. Here's another thing, that's a bit worrying when you consider a child could lose a hundred mils of lung function. This is a very old study, well, not old but it it goes back in time. This is a children's health study in California and they followed longitudinally children in three waves. The first wave was between '94 and '98, then the second wave, '97 to 2001, third wave, 2007 to 2011. And they'd looked at small lungs, clinically small lungs. So if we looked just the shady area, this is the number of children who had lungs less than 80% of unpredicted. This is clinically significant. And you can see when they started the study back in the mid nineties, it was about 6%, and when they went back 2007 to 2011, it's fallen by half. Over this period of time, air pollution has fallen, and these associations are linked to the fall in air pollution. So this means there's a benefit, but actually what this means is even more significant.'Cause what they are doing by reducing air pollution is preventing the accumulation of vulnerability within the population. These small decrements in organ function will manifest in 20, 30 or 40 years time in a greater susceptibility of these children harmed now to develop the diseases of aging as they move through their life. Now, all of those studies demonstrate that if you regulate, it works. But regulation could be quite unpopular, and so, I thought I'd just throw this up just to see how much rage I can produce. Now obviously, the ultra low emission zone is designed to accelerate the rate of uptake of vehicles with lower emissions, yes? Fine. It starts in the center of the city in the congestion charging zone, and then last October, it was expanded up to the north and the south circular. And bear in mind, the south circular is where Ella Kissi-Debra lived. And the reason we are doing this is try to deliver better health, and then last week, because everything seems to be contemporaneous with my talk for some reason, it was decided that it would be expanded on the 29th of August to all of the London boroughs. And as of this morning, four London boroughs are appealing the decision. This is really interesting, it's that issue that I think Harold Macmillan was getting to, yes? This wide set of issues. There is no doubt, I'm just a scientist, I'm not getting involved in the politics but I can say some definitive things, yes? Air pollution from traffic is bad for your health, having really bold traffic mitigation methods which reduce traffic for pollution will benefit health, absolutely that's the case. I would also add that most of the people in London are suffering from air pollution that they didn't generate themselves, and very often the people who are suffering the most are the most disadvantaged and the individuals who have the least agency in reducing their own exposures to air pollution. Then people can make their decisions about how this progresses. Two final thoughts. The first thought is that there's nothing new under the sun. This is John Evelyn, founding member of the Royal Society. This is an essay he wrote in 1661, "Fumifugium," it's to do with air pollution in London. He makes some really salient points all the way back in the day. Number one, if you want less pollution, use cleaner fuels. That sounds sensible. Number two, we should separate vulnerable populations from the sources of pollution. I don't know, let's put that into a modern context, it probably isn't a good idea building cheap, affordable housing next to the busiest roads in London and then targeting young families. That could never possibly happen. And let's go one further, throughout the entire essay, he makes the point that actually investing in the environment actually is to the benefit of the city and to the city's economy. A healthy, motivated workforce is an economically productive workforce, and he makes the argument that it's almost, doesn't use the words, but almost a human right or something which we should expect that we can be delivered clean air, which again, is interesting because on August the second, the UN actually made a right to clean environment and clean air a human right. So that now sits in our sort of international clause. And then I will finally leave you with this. I live in South London, I live in Lewisham, I walk home often from Suffolk. This is on the Woolworth Health Center. It is the translation of coat of arms of Lewisham Council where Ella Kissi-Debrah grew up. I think this is a fundamental message for our times and in how we consider how we use our environment and how we tackle air pollution, because the health of the people is the highest law, and that that's the balance we should maintain when we consider how we tackle air pollution moving forward into the 21st century. Thank you.(audience applauding)- We have time for a couple of questions, so I'll start them off with some that have been submitted online before I open it up to the floor. So the first one is,"Could a great smog happen again? Given the increase in urban domestic burning and rise in the sales of diesel generators, how likely is it that we will see a hazardous smog again? Is it possible?"- All things are possible but the question is really to do with our current cost of living crisis and fuel security issue and the concern that people are going to begin to repurpose their fireplaces to heat their homes in whatever way they can, yes? And under those circumstances there are many people who are concerned that we may have, maybe not a citywide smog but little areas, little pockets of significant air pollution because of those those measures people are likely to take. And that's also where they're getting to their diesel generators. This is clearly, I think, I may be misrepresenting the person online, but it is a real issue, people are very concerned about this over the next year, year and a half. And again, bizarrely, it's an energy security issue to do with the economy, much like the London Smog was an energy security issue to do with coal and who got the good coal and who got the bad coal, yeah.- So kind of related, I have a question here on wood burning in homes."What do you think is the best way to educate the lay public and the government on the dangers of the pollution that is caused by this?"- So, you know, I don't want you to think I'm a one trick pony because I've put Scandinavians in boxes and exposed them to diesel but I've also done it to (indistinct) smoke, yeah? And the responses you get are very variable, yes? If you use the driest product with the most highly specified wood burner, yes, with perfect extraction, then actually you get very minor symptoms. But the moment, the absolute moment, any specific parameter goes out slightly, yes, it's as harmful as diesel. And once something is in your home, who's regulating it, yes? It could be a perfect stove on Monday and not a perfect stove on Tuesday, and in fact, how you load it may actually affect its parameters, yes? So I think that there's a real potential issue about wood burning. And also, the other issue is I think there's an element that people may be self polluting to a certain extent, but what about the person who decides they're going to have a wood burner next to the house of somebody has an asthmatic child with difficult to control asthma? Where's the legal right of that individual not to be exposed to something which is demonstratively harmful to their health? If you went up to them and threw peanuts at a child with peanut allergy, it would be very clear what side the law was on, yes? With wood burning, not so. So I think wood burning is a bit of a blind spot in policy at the moment and it needs a hell of a lot more attention. Because it's going to happen, but it's going to have to be really tightly regulated, yes.- [Audience Member] Yeah, I enjoyed your lecture. More questions about, we share a diesel van, a full galaxy, and you put AdBlue into it and that's meant to cleanse the exhaust. Could you say anything about that? Do you know of that? It's a liquid, it has a separate tank next to the fuel tank, the diesel fuel tank, and that's meant to clean the exhaust emissions.- To a certain extent. And one of the things I didn't talk about was I've spoken about regulation and the other aspect is technical innovation. And the reason I didn't dwell on technical innovation is it has a checkered history, yes? The tele innovation often promises a lot and delivers something which isn't so good or creates a different problem, yes? So for example, certain additives will sort of like remove NOX and NO2 from the fuel, and that's a good thing, yes? But they may also change the nature of the particular emissions which occur. And then there were other issues which I find really odd. I mean, about 15 years ago in Europe actually, people added something called Cerium dioxide to diesel fuel, yes?'Cause it caused a more efficient ignition, yes? And so it was more effective, fuel efficiencies went up. And when they went to introduce it to the United States, the United States said,"That sounds fantastic, show us your safety data." And they went, "What safety data?" And they went, "You haven't just released this into the environment without testing whether it's safe." And there was no requirement for them to do it over here but they couldn't do it in the States. So I'm always a little bit cautious about adding things to fuel where we don't fully know what the pyrolysis high temperature products of that will be and whether will impact on human health, and I think we have historically been incredibly cavalier. Having said that, there have been some things which have been accidentally remarkably successful. So we are very concerned about very small particles, yes, and the introduction of low sulfur fuel, yes, actually caused precipitous fall in the number of very small particles from exhausts. But not in a particularly deliberate way, almost in an accidental, oh look what's happened, yes? And so I think perhaps what we do with all these new engine technologies, we need probably to have somebody who sits over the top of them and does some proper evaluations. I really sort of like, part of my background is thinking about drugs and how you introduce drugs. I think we need something similar when we introduce things which are exposed to the population to make sure they're safe first rather than waiting to discover at a population therefore they weren't safe and then we have to pick up the pieces. Does that answer your question?- [Audience Member] Yeah.- Oh good.- [Audience Member] I am also South London, and in my area there have been a lot of road closures in the name of improving pollution levels. But on the other hand, objections have been made saying that because they prolong journey times by making people take more circuitous route, they actually overall increase pollution. Have you looked into this at all?- Yeah, I do. And I can answer it on two levels, yes. The first is in a purely empirical scientific point of view. Wherever traffic management systems have been introduced, which have made driving more difficult, and everybody's assumed there must be some sort of displacement effect, there's no evidence for it. Really there isn't, it's bizarre, yeah? Everybody assumes there must be 'cause the traffic which exists must simply be being pushed down different routes. But the evidence is if you make driving difficult, people just, especially in central areas, go, "Forget it," and they drive less. The reason I would be not absolutist on this is because you kind of need people to play the game, and if they don't, yes, you've got a problem. So if you had a child who was an asthmatic, and even if a few vehicles changing direction didn't make more pollution but they were going past your house, I would think you would have every right to be a bit upset about it. And in reality, these little road closures are effectively little Band-Aid on a really obvious problem. You could make everything much more equitable just by having rules which were applied equally everywhere. If you wanted to encourage people to drive less, you could use road taxation for road usage, yes? Then you wouldn't have to have things like the ultra emissions only congestion charges, it would simply be function. And then once you had that in place, you could use the taxation system for levies for people who you thought potentially had very vital jobs which needed them to have transport, yes? But at the moment everybody does something a bit different here and there and it creates the impression of inequality and winners and losers, and actually there are people out there who are looking for those opportunities to try to undermine action against sort of air pollution in cities because they're vested interested in those areas because they think it's going to be anti-car, anti fuel consumption. So we have to be a bit careful, but the data says, "Don't worry about it." I say, one death is too much.- [Audience Member] You looked at your meter on your phone, it said "low." I have one too, I don't believe it, I hold this thing up in Holland Road near where I live near the Westway and it's always low. Does the person making diesel vehicles have shares in these meters?(audience laughs)- So I'm not great at conspiracies, and the reason I'm not great at conspiracies is because, generally speaking, most things are chaos and muddle a mess, and it's almost impossible to believe that anybody's sitting on top of all of this and having some form of conspiracy. I think your point is this, and it's a really interesting one, the air pollution sort of banding, you know, the traffic light system, is based on protecting somebody who for example has asthma or COPD from short-term episodes. And they have a different level to those long-term effects, but nobody has worked out how to illustrate those long-term effects in those maps. Or to put it another way, in September of last year, the WHO revised down all of their guideline levels based on what is a safe level of NO2 and PM2.5. So now the WHO guideline, the safe level should we say, is five micrograms per meter cubed of PM2.5 as an annual average, that went down from 10, and then NO2, which was 40 micrograms went down to 10. So it actually fell by four. Now on that basis, using that traffic light system, you wouldn't leave your house. Because London would be red the whole time 'cause you'll be saying, long-term, all of this air quality is bad for your long-term health. But the difference is how do you show both? And that's kind of where I think it's lost. So I think it's imperfect rather than, and I can guarantee,'cause I know the people who work on these websites and they really wouldn't look the way they looked if they were getting backhanders.(audience laughs)- [Audience Member] Which one do you have?- Well, look, I'm going to just say I use the London Air Network because that's run out of our group at Imperial College, and associated with that, we have Breathe London, which is a small local sensor network, but local sensors are useful, but they're not always absolutely right, but they're indexed to our actual air quality monitoring stations, which are gold standard, yes? But there has been a proliferation of stuff, and I do worry, and I shouldn't say this, but people go out and they buy air quality sensors, yes? And they walk around and they go, "Oh, look at this. When I'm standing next to the road it's really high, and now I'm in the middle of a park, it's really low." Now at that point, I think you're almost able to throw your air quality sensor away because you've learned a fundamental lesson which will result in you just actually being able to use your eyes and a bit of common sense, yes? That doesn't capture episodes and all those things you'll be predicted, yes, but I do think that people have a little bit too much faith in the local sensors they're getting when actually they're not absolutely precise or used effectively.- Thank you.- Thank you. That's all we've got time for tonight, so please join me in thanking Dr. Mudway once again and thank you all for your time.(audience applauding)