Introduction to Air Pollution

Introduction to Air Pollution

In this module, I'm going to introduce you to some basic concepts of air pollution, but before we do that, I'd like you to take a deep breath.

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Now think about what was in that air you just breathed, if you have any science background, you might know that that are was about 78% nitrogen and about 21% oxygen, but what else was in there? Over my shoulder here, you can see I'm standing next to a power plant smokestack, what's coming out of there that's going into my breathing space? The good news about this particular plant is the emissions are mostly carbon dioxide. But for millions of people around the world plants like this and other sources emit lots of different hazards that people breathe in.

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So air pollution is not a single chemical, it's actually a mixture of thousands and thousands of components collectively those components are thought to kill about 7 million people every year. Now, we're faced with a number of big air pollution challenges today one is stratospheric ozone depletion. Now this is one where we've actually made some huge progress, you may have heard about the hole in the ozone layer that emerged in the 1970s and 80s. We actually took some steps to prevent and actually arrest the growth of that ozone hole and have made some huge strides there. Where we haven't made strides are things like atmospheric deposition. So power plants like this other sources put air pollution into the air, it travels over time and space and unfortunately out of that are come things like mercury and persistent organic pollutants that are harmful to human health. We also have issues in city environments like an arbor of urban smog, particulate matter ozone that we can breathe. A huge defining issue and environmental health is climate change resulting from greenhouse gases. We're fortunate this smokestack puts out almost entirely carbon dioxide, but that's not the case with many plants, and even though carbon dioxide's not directly toxic it's very much driving global climate change. Finally, there is actually no place to run even going home indoor air pollution turns out to be a substantial source of exposure for many, many people around the world.

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Air pollution is not a new problem, if we go all the way back in time to 61 AD the famous Roman Seneca, was noted as talking about the pestilential vapors and soot that emitted from the chimneys in Rome. Fast forward 1000 years and Moses Mainmonides was quoted as talking about the are in cities becoming stagnant and turbid, thick, misty and foggy. We've talked previously about the great London Smog of 1952 that was in the United Kingdom, but we had our own event. Actually a series of them starting in 1948 in Donna of Pennsylvania where 20 people were killed by air pollution. In 1966 in the city of New York something like 3,000 people were made substantially ill, and up to 10% of the City's population was impacted by a smog event there.

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Now there was a highly influential study that was done looking at the effects of air pollution on adults in the United States in the 1970s and 80s, this is the so-called Harvard Six Cities study. And this was one of the very first studies that very strongly and unambiguously showed a positive correlation, between levels of pollution in the air of a community and mortality in that community. And so what they did was study six different cities including a city called, Steubenville, Ohio. And looked at the average lifespan and the estimated loss of life among people in these different cities, and I'll sort of jump ahead to the conclusion. They found that in Steubenville, Ohio people lived an average of four years less with those highest air pollution levels compared to Portage Wisconsin the city in the study with the cleanest air. So this study again kind of definitively showed that there is a link between chronic exposure to air pollution, and mortality related to cardiovascular outcomes. So diving into this a little bit more, these are different graphics showing the relationship between different measures of air pollution and the six cities that I mentioned. Steubenville, Ohio Portage, Wisconsin, Waterton, Massachusetts, Topeka, Kansas Harriman, Tennessee in St. Louis, Missouri. I don't want to get bogged down on the details of each of these six specific graphs, but I do want to note that if you look for the P, that's Portage, Wisconsin. You're going to find it in the lower left corner of all of these graphics, so for that least polluted city in terms of air pollution. They tended to have the lowest effects observed, and I'll also ask you to look for the S. That's Steubenville, Ohio and you'll see they tend to be in the upper right hand corner of each of these graphs. They had the highest air pollution and they suffered the highest impact, and we can also see a generally linear response between air pollution levels in these cities and the health impacts picture.

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So a very important point I want to illustrate here is that air pollution is not static, it varies over time and it varies over space. So what you're looking at here are two images of air pollution levels, one at the national level and one zoomed in on the southwestern United States. And you can see that as the graph rolls forward in time over the course of a day, the air pollutions are fluctuating. We start with a very strong air pollution emission in the upper left corner of national map a giant wildfire occurring in Canada. And you can see the air pollution there actually spreads out over the course of the day. And looking at the right hand side to the Southwest you can see there's another plume of emissions in Northern California again from a wildfire. But what you'll also observe over the course of the day, is that the colors in both images tend to get more vibrant and the air pollution spreads out. So again, pollution is not the same over time and it's not the same over space, and that's that's what makes it so very difficult to understand from an environmental health perspective.

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If we zoom out to the global level here, we're looking at a map of air pollution levels in different cities around the world. The green coloration on this map indicates cities with safe or acceptable amounts of air pollution, and the yellow and the red dots indicate areas with less safe or harmful air pollution. And again, you can see the air pollution is not uniformly distributed, Western Europe United States. We have relatively low levels of air pollution compared to specially to South and East Asia. So even at a global level we see massive variations in the air pollution.

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So we can also look at the health impacts of this air pollution at a global scale. So here we're looking at two images one of the rate of deaths from air pollution by country around the world. One of the rate of disability adjusted life years, and you see a similar pattern for both outcomes North America South America much of Western Europe Australia. These places we know have low exposure and they also have lower burdens of disease. Whereas sub-Saharan Africa, South Asia and East Asia have the highest levels of air pollution and also the highest health impacts.

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Unfortunately, we know that the burden of air pollution is much stronger in low income and more developing countries than it is in high-income developed countries. There's a couple of different reasons for this, one is, low income countries tend to have much higher household exposures. So, imagine that the only way you have to heat your food and to heat your home is an open fire in the middle of your house. You're going to have substantial exposures to particulate matter the whole time that fire is burning, compared to a home where you have central air and heat and the exhaust is emitted outside.

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We also know that low-income countries tend to have much more rapid development in terms of industrialization or urbanization into city environments. And the development of their transportation infrastructure that can result in unchecked air pollution.

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There's fewer preventive services and less Health surveillance available in low-income countries. There also tends to be higher maternal exposure during pregnancy. Imagine you're a pregnant woman working directly over a wood stove inside your house, you're having a huge exposure. And we also tend to see much higher childhood exposures in low-income nations compared to high income Nations. So these factors and more make it critical for us to look at air pollution, not just on a low local level, but also on a global scale.