Tackling Air Pollution


When NASA’s Terra satellite acquired this image on December 7, 2013, thick haze stretched from Beijing to Shanghai, a distance of about 1,200 kilometers (750 miles). For comparison, that is about the distance between Boston, Massachusetts, and Raleigh, North Carolina. NASA 

Around the time of the summer 2008 Olympics in Beijing, we started to hear about air pollution in Chinese cities. To be clear, this was not the start of air pollution in China – it had been around for a while. But about this time, accurate air quality measurements began to be taken and there was some outrage that a sporting event should be held in a place containing levels of particulate matter 10 to 20 times the level deemed safe by the World Health Organization.

This sense of outrage has certainly not decreased since then. It has become common knowledge in China that living amid fog-like air pollution has disastrous long-term health effects, and the observation that government officials possess elaborate and expensive air filtration systems has not been advantageous to public opinion. Some action has been taken in recent years, but it is unfortunately difficult to improve the air in short order. Most of the pollution in Chinese cities comes from electricity generation, especially coal power stations, heavy industry, and vehicles that lack exhaust filters and burn low-quality fuels. Thus, a somewhat substantial economic transformation will be required to permanently end the extreme air pollution events which occur regularly in industrialized areas.

What is the history of air pollution and what are today’s polluted cities in China, India and Africa like compared with historical conditions in the industrial West? In December of 1952 London experienced an extreme air pollution event now termed the “great smog.” This was only the latest in a several hundred year-long series of polluted periods, but it was unique in that it was definitively linked to the premature deaths of approximately four thousand people. In 1956, Parliament passed the Clean Air Act, which established some of the first limits on emissions in urban areas.

During the second half of the 20th century air pollution in Europe and the United States has more or less steadily decreased. In the 1960s, New York City experienced air pollution which reduced visibility as much as a dense fog (the term “smog” was coined in the early 20th century as a combination of “smoke” and “fog”). Today, in 2014, pollution in New York and most other cities in the United States and Europe is, for the most part, low. This is to some degree the result of heavy industry moving to cheaper parts of the planet, but it is mostly due to effective regulations requiring decreasing emissions of particulate matter and pollutants which cause urban haze and acid rain.

There are a few primary categories of pollutants. Some are chemicals: sulfur dioxide is the primary cause of acid rain, and nitric oxide and nitrogen dioxide are emitted by vehicles and are essential in the formation of urban smog and ozone. Ozone is a health threat at the surface but it is more commonly known in relation to the high altitude ozone layer, our protective shield against the sun’s ultraviolet radiation. And no, by reducing pollution we are not having any effect on the “good” ozone twelve to fifteen miles above the surface.

All air pollution is harmful to human health, but one type stands out above the rest: particulate matter, especially that which is very small. These tiny particles – less than 2.5 micrometers across, or about one twentieth the width of a human hair – can become lodged deep in our lungs, triggering a variety of unfortunate respiratory and cardiovascular health emergencies. The long-term health effects of extreme pollution exposure are similar to smoking – asthma, lung cancer and heart disease. In 2012, the World Health Organization estimated that air pollution resulted in about seven million premature deaths worldwide.

Reducing pollution is simple. Emissions from power plants, especially those fired by coal, transportation and industry must be reduced. This can be done by installing filters inside power plant smokestacks, using cleaner burning fuels in vehicles, and decreasing the concentration of emissions sources in and around urban centers. This has been successfully accomplished in Europe and the United States; pollution in New York, London, Paris and other cities was very high fifty years ago, but is for the most part low today. And we drive, fly and use electricity more than ever before.

As the story in the West shows, economic growth is not inextricably linked with pollution. We should remember that the environment is an economic asset and in the slightly longer term it is in no one’s interest to see it degraded. That said, of course the economy must grow, as this growth is the way to transform society for the better. The point is we want both – at the same time! This is not impossible, although it is true that it is much easier in developed regions where individuals are not dependent on highly polluting sources like wood and mud-burning stoves. But, in places like eastern China, reducing pollution should not necessarily be difficult; it mostly requires a choice, one which will hopefully be made sooner rather than later. 

The image above shows air quality index measurements for PM2.5 (particulate matter) across the planet taken a couple weeks ago - the pattern is typical, with good values across the U.S. East Coast, slightly worse (yellow) values across the U.S. Southwest (likely due to concentrated industry in south Texas and maybe some dust), moderate values across Europe, and then very bad values across eastern China. Similarly bad (red to off-scale) values would be seen in India and central Africa if there were more monitoring stations.



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