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Pollution from Megacities Decreases Air Quality in the U.S.

Scientists track air pollution on a global scale and measure its potential health impact against U.S. EPA standards for air quality.

Rio de Janeiro, an example of a megacity-- by Joann Jovinelly

The Gist

China is a leader in manufacturing, but it is also releasing enough emissions to significantly increase U.S. air pollution, says a new report by the World Meteorological Association (WMA).

The WMA study examined air pollution and its migration from megacities around the world (those with populations greater than 10 million). The findings support earlier claims that air and ground water pollution is both a local and regional problem, as well as one that requires global solutions, such as the need for consistent international air quality standards that are not yet in place. Worse, increases in air pollution are expected to increase along with projected population growth in those same cities, many of them in developing countries.          

According to Megan L. Melamed, one of the lead authors of the WMA report, researchers now have ample data proving that emissions from megacities around the world have an impact on regional and global climate as well as air quality.

For instance, harmful particles polluting the air in western U.S. cities routinely drift to North America from China, often pushing them beyond the ozone limit. Such an increase could have a variety of negative short-term and long-term impacts, such as increases in acid rain, temporary decreases in visibility, and an increase in the speed of climate change. Americans with existing respiratory conditions like asthma and COPD could also be negatively affected.

Source and Method

To make the determinations regarding air pollution levels, authors of the WMA study used satellites to track smog and then compared that data with air samples collected on the ground at the same time. Among the challenges scientists faced in this study (and one of the reasons why the WMA study is so groundbreaking) was the effort involved in bridging chemical and climate modeling and methodology across many different countries.

The Takeaway

The need to establish international standards for air quality has never been clearer. With Asian megacities and other similarly dense population centers around the world, such as those in South America, air and water pollution is increasing rapidly. The health impact of such increases is not yet fully understood, yet along with climate disruption, it remains among the most important reasons to control manufacturing and put policies in place that can reduce carbon emissions and maintain air quality standards for all.

Other Research

According to a 2012 study in the Journal of Geophysical Research, air pollution from China emissions directly contributes to U.S. ground water pollution by as much as 20 percent.

Similar findings were reported by Meiyun Lin, an atmospheric chemist at Princeton University in New Jersey who also analyzed air-quality data from satellites and compared it to ground measurements over several days.

The U.S. Environmental Protection Agency’s (EPA) guidelines for air quality standards state that dangerous chemical compounds should not exceed 75 parts-per-billion in the atmosphere. Lin’s findings sometimes found a greater concentration of chemicals in air samples taken in the northeast. Lin attributes these results to the heavy amounts of manufacturing in Asian megacities.

Daniel Jaffe, a chemist at the University of Washington Bothall, also says the air pollution in U.S. cities are increasing at a rate of 0.8 to 1 percent annually. That figure has been called “significant,” and it also has physicians concerned with controlling pollution-related respiratory disorders like asthma and COPD.

Fortunately, satellite imagery can help the U.S. government alert citizens days in advance of poor air quality, especially since halogens (fluorine, chlorine, bromine, iodine, and astatine), are harmful carcinogens for people and animals. Those chemical compounds are often suspended over U.S. cities for extended periods depending on weather conditions, but with ample notification, people with breathing problems can plan to stay indoors.

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Tags: Awareness , Global Health , Public Health & Policy

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