Anyone living in the U.S. for the past decade may have noticed an encouraging change in air quality.
These NASA satellite images demonstrate the country’s reduction of air pollution, or more specifically, nitrogen dioxide, a pollutant linked to adverse effects on the respiratory system. The images show a marked decline in nitrogen dioxide concentration over much of the eastern U.S. between 2005 and 2011.
NASA calculated that in those six years, Philadelphia experienced a 26 percent decrease in the gas, which is produced primarily during the combustion of gasoline in vehicle engines and coal in power plants.
Declines were also noted in the western U.S, including Denver, Los Angeles and San Francisco
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