Post first published February 20, 2016, updated May 8, 2017.
Poor air quality?! How come? I'm in the middle of the forest!"
Have you ever watched weather on TV or an app and wondered how meteorologists put together such amazing information? If so you probably know that local weather is greatly affected by meteorological changes on larger scales, such as fronts and jet streams. We’ve also discovered that these large-scale currents in the atmosphere not only change the weather, but also carry air pollution to much longer distances than from city to suburbs. But how does this happen?
Air pollution moves and disperses. Some of the first records of regional scale anthropogenic (man-made) air pollution refer to the effects of acid rain – a wet or dry deposition of acidic material from the atmosphere. Acid rain can include rain, snow, fog, hail, and even dust. It can be a naturally occurring phenomenon (for example from volcanoes), or be caused by NOx or SO2 emissions from coal and fuel burning. Its corrosive effect was first described in the 17th century in smoggy cities in England, but only in the 1960s did the U.S. begin to recognize acid rain as the cause for negative environmental and ecological events. Example: every winter since 1998, Harvard University covers some of the bronze and marble statues on its campus with waterproof material, in order to protect them from damage caused by acid rain and acid snow.
And about 40 years ago reports started coming from Canada, the U.S., and Scandinavia about “dead lakes.” The reports found that these lakes had become too acidic for fish eggs to evolve, resulting in very low numbers of fish. It turned out that coal burning, which was quite extensive at that time, was responsible: the wind carried away high concentrations of SO2 over long distances (hundreds of miles), transformed it into acids, and when it later rained over the lakes, it polluted the previously clean water.
Asian Dust/China Dust/Yellow Dust
A rather recent large-scale air pollution phenomenon is the yellow dust of Asia. The fast and extensive industrial development of China means that large amounts of pollutants are emitted into the air. Intense dust storms, full of industrial pollutants, pick up dense clouds of soil particles. These clouds at various times carry many toxic pollutants. And the swift, powerful winds that blow over the deserts of Asia pick up these deadly dust particles and carry them eastward over China, Korea, and Japan. The effects of these yellow dust storms are massive in the countries of Southeast Asia: very low visibility, significant health effects even in healthy people, along with damage to plants and soil because of acid rain. Plus, in many instances, the pollution reaches the U.S.
Air Pollution in the U.S. from Asian Countries
Smog, which harms human health, has been on the increase in the western U.S., coming from China, India, and several other Asian countries, says a USA Today article. This has taken place over the last 25 years, says an NOAA scientist, in the spring, when wind and weather patterns push Asian pollution across the Pacific Ocean.
You don’t have to go far – along almost any border between countries – to find transport of air pollutants. The main cause of these phenomena is big industrial complexes, found, for example, in Eastern Europe and Southeast Asia. In the 1970s, much of the world knew about the consequences of pollution emissions to the atmosphere, and a number of countries formed agreements to try to reduce them. In 1979 in Geneva, 34 governments and the European Community signed the Convention on Long-range Transboundary Air Pollution. This convention defines the general principles for international cooperation regarding reduction of air pollution, as well as encouraging research and policy on this matter. In 2002, the 10 ASEAN countries signed the ASEAN Agreement on Transboundary Haze Pollution, made to reduce haze pollution in Southeast Asia, which is caused mainly by land clearing for agricultural uses via open burning.
How Pollution Travels Through the Hemisphere
If you want to investigate air pollution on an even larger scale, look at the 2010 document “Task Force on Hemispheric Transport of Air Pollution,” published by The European Monitoring and Evaluation Programme (EMEP). This document presents measurements and modeling findings that describe how air pollutants travel between continents: westerly winds transport emissions from East Asia to North America, from North America to Europe, and from Europe to the Arctic and central Asia. See the figure below for more info.
About the author: Shaked Friedman holds a B.Sc in Environmental Engineering from the Technion. In the past two years Shaked has been developing real time air pollution analytics and dispersion algorithms at BreezoMeter.