The air we breathe contains particulate matter from both natural and anthropogenic sources. In the United States alone, thousands and thousands of premature deaths are recorded each year, but the US Environmental Protection Agency (EPA) has noted a significant decrease in this figure, as well as in the amount of particulate matter contained in the atmosphere.
And while the number of premature deaths associated with exposure to particulate matter exceeds the number of deaths from accidents on the roads of the country.
The Clean Air Act of 1970 and additional amendments of 1990 address the health effects of particulate matter, in particular by regulating emissions and promoting research on cleaner alternatives to energy and transport. In 2011, the EPA announced that the legislation is responsible for significantly reducing particulate matter in the atmosphere, estimating its effect at more than 100,000 lives saved annually from 2000 to 2010. However, the report did not address organic aerosol, which is the main component of atmospheric particulate matter. Organic aerosol is obtained directly from the combustion of fossil fuels (for example, in vehicles), the combustion of coal for residential heating, and forest fires. It is also chemically produced in the atmosphere during the oxidation of both natural and anthropogenically produced hydrocarbons.
Researchers at the Massachusetts Institute of Technology found a sharper decline in organic aerosol in the US than previously reported by the EPA. Their work has shown that these changes are likely related to anthropogenic or human behavior.
Observations show that the decrease in organic aerosol was six times greater than in 2000-2010, according to EPA reports.”
Using data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, the researchers found that organic aerosol decreased throughout the country in both winter and summer. This decline is quite unexpected, especially in light of the data on the increased frequency of forest fires in the summer. But the researchers found that despite wildfires, organic aerosols continued to decline in both urban and rural areas. The absence of an obvious natural reason for the decrease in organic aerosol indicates that the decrease had anthropogenic causes. Along with the decrease in organic aerosol, there was a similar decrease in other atmospheric pollutants such as nitrogen dioxide and carbon monoxide. In addition, the similarity of trends in both urban and rural areas suggests thatthat the decline can also be the result of changes in people's behavior.
The findings of the researchers were published in the article "Causes and Consequences of Reducing Atmospheric Organic Aerosol in the United States" in Proceedings of the National Academy of Sciences.
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