 My research question is related to the air pollution that mankind is emitting into the atmosphere. We have a growing number of people, we have a growing number of industries, we have a lot of traffic, putting exhausts and all kinds of things into the atmosphere. And the question first is, what is happening with all this air pollution? Where does it go? Is it being converted into something that can be easily removed so that it doesn't pollute the atmosphere anymore? Or is it being transported across national boundaries so that the air pollution from one country can affect also the other country and so on and so on. Maybe even from one continent to the other. And the other question is, related question is, what does it do to people? So there is a lot of air pollution in the atmosphere, that's obvious. You can see that every day and in some regions of our globe, air pollution can be very heavy. And the question is, how does the air pollution affect the health of people? And actually, the health of people, if it is affected, it actually means that people can get seriously ill from air pollution and can even lead to mortality. People die from air pollution. I call this also passive smoking type of effect from air pollution. So the question is really, how does the air pollution get into the atmosphere? What happens to it? How does it affect people? And in this specific case, how does it contribute to premature mortality of people due to air pollution? Yes, the method we use is to estimate how much worldwide air pollution exposes to people. So how much are people exposed to air pollution? And since air pollution moves around in the atmosphere very quickly, we need to do this on a global scale. We need to know how much air pollution goes from China to the United States and from the United States to Europe, so we need a global view. Now, we have a number of measurement stations in Europe, for example, in Germany, but also in the United States and in some other parts of the world. But in most of the world, actually, we do not have this information. So the question is, how do we get a global view of air pollution? And this can be done by using the data, the measurement data that are available, but they need to be integrated into a larger picture. And for this, we use models. So we use models that, for example, are also used for the prediction of weather. They are global models that predict the weather, and that can be extended with all kinds of processes that deal with air pollution. And the second important thing is that recently, I would say the last decade or the few decades, also satellites have become available that give us information about air pollution on a global scale. Now, a problem with the satellites is that they give a global information, but the information is of low resolution, so there is not a lot of detail in this information. So the thing is, we need to put these things all together in order to get a global view. So we assimilate the data that we have into the model, so we steer the model by using the data, and we use the model to get a global view. And this gives us an opportunity to get a global concentration field of all the air pollution that people are being exposed to. So that's the first important step. We need to know how much people are being exposed to. And then the second step is that we need to know how does this exposure affect the health of people? Now, there we are not actually medical doctors, we are not in medical research, so there we work with people who are in the public health research sector. So with epidemiologists, and they have used many thousands by now by millions of data of people that they have been following in time in order to study how much their health is being impaired by air pollution. And then we combine these data in order to have the global view and the global exposure of people to air pollution, and then calculate how much their health is being affected. An important point is also that people are being affected by air pollution and also by other diseases in different ways in different continents. So the health condition of people in Africa is different from Asia and is different from the United States and is different from Europe or in Germany. So there we use data that we have from the World Health Organization that provide information on the country level health of people. We call this the baseline mortality rates related to specific diseases. Now by combining all these data, including the data on how many people live where, so we also need what we call demographic data, population data, by combining all these things we are able to estimate how much people are being affected by air pollution and how many people die from which disease related to air pollution. The key finding of our paper is that many people, namely 3.3 million people per year die because of air pollution. I call this passive smoking on a global scale. And to put this in context, if you take HIV, AIDS and malaria together, about one and a half million people die per year. So from air pollution we have more than double that amount. It's more than 3 million people per year that die from air pollution. Now the next thing is of course what are the diseases that are related to this premature mortality? We have zebrovascular disease which leads to stroke. We have ischemic heart disease which leads to heart attacks. So this is about 75% of all the premature mortality related to air pollution. It is about similar as smoking. And the other 25% are respiratory disease. This can be in small children, but it can also be in older people like with lung cancer or chronic obstructive pulmonary disease. So these are the main diseases that cause premature death related to air pollution. The next question of course if you want to do something about this, we need to understand the sources. How can you most effectively do something about the sources? Now this is where we can use our model and we can distinguish a number of categories. We have natural categories in some areas like where you have deserts in Africa or the Middle East. You have a lot of dust in the air. But in most urban environments it's actually another reason. And it is traffic is one cause, but a major cause actually are small fires. We call this residential energy use. On a global scale about 75% of all the premature mortality related to air pollution is in Asia. And in Asia, especially in South Asia, this cooking and heating produces an immense amount of air pollution. So people are exposed to immense amounts of air pollution from very small sources. But there are many people creating these small sources and these sources are very polluting. And all together this creates an enormous small plume that people are being exposed to. So that's in Asia, in Eastern Asia, in China for example, it is more traffic and energy production also using coal. This is also in the United States. And especially in Europe we have a large contribution also from agriculture. Agriculture produces a gas called ammonia from animal husbandry and from fertilizer use. And the ammonia creates particles in the atmosphere. And it's actually the particles who are the bad guys causing the problem in terms of premature death because of air pollution. It is fine particles that penetrate deeply into the lungs and even into the bloodstream that cause these problems. And ammonia is extremely effective in making these particles. So in Europe for example, we find that something like 30 to 40% of all the premature mortality is related to agriculture. We think that these findings are important and relevant to policy making to people because now we have a tool in our hands that can tell us how you most effectively reduce this problem. Because if you only measure air pollution you know how much is there, but you don't know how to control it. You need to know what are the main sources that cause this problem. And by using our model in combination with for example the satellite data we can calculate what are the main sources and how you can most effectively reduce the air pollution that causes health effects. And what we find is that we have residential energy use in Asia which can be for example be reduced by distributing cook stoves like in India. There are large programs that give people cook stoves so that the burning is more efficient. To provide clean fuels is very important. Actually in India there is a big program providing clean fuels and this will help reduce this problem. And in Europe for example we need to do something about the emissions from agriculture. Now of course it will not be possible to tell agriculture to stop doing this but I think there are methods that will reduce the amount of ammonia that comes out of agriculture like not spraying all the manure over the land and so that all the ammonia gets into the air use actually the manure to make biogas or also have more efficient methods of applying a fertilizer on the soils to make sure that the ammonia that is needed as a fertilizer gets into the soil and not gets back into the atmosphere. So there are methods to deal with these problems and I think our research is helping to identify the problems and to make the policy makers and the public aware of how to most effectively deal with air pollution and prevent it from killing people. So the outlook is that we need to reduce uncertainties. I mentioned that there is a number of 3.3 million people per year dying from air pollution but in reality actually there is an uncertainty of about plus or minus 50%. So it could be 1.6 which is still a large number but it could also be 4.8 million per year which is a huge number. So we need to reduce these uncertainties also to tell policy makers where and how to most effectively reduce the problem. And the second issue is we need to discuss also with policy makers and the public what are the levels that are acceptable? Where do we draw the line? For example in Australia it's allowed to have 8 micrograms per cubic meter of fine particulates in the air per year on average. In Canada it's 10, in the United States it's 12 and in Europe it's 25, it's twice or more than twice in the United States. So people here are not stronger, they're exposed to more air pollution but actually the per capita mortality because of air pollution for that reason is higher in Europe than it is in the United States. So we also need to work with legislators not only to show them how to reduce this problem but also to convince them of the fact that they need to put in place laws that prevent air pollution from killing people. 25 micrograms per cubic meter is much too high. The third issue for the future is that we also need to look at low levels of air pollution. Of course at some point air pollution will be reduced but still the question is how much air pollution can people accept? How much is not affecting human health? And the current thinking in the medical and epidemiological community is actually that there is probably none. So all air pollution is causing health problems. This is a big issue because now we not only have a problem within the cities where air pollution is high but then in that case also have a problem outside of the cities where the air pollution is lower and probably you need to have other measures in place to take care of that type of air pollution as compared to city air pollution. So all in all I think we need to reduce uncertainties become more precise in how we define what is still acceptable and also look at low concentrations and see what low concentrations of air pollution lead to in terms of human health impacts.