Is U.S. Air Quality Improving? Here's What NASA Found

NASA reports that there has been a steady decline in air pollution throughout most of the eastern U.S., including Washington, D.C., and the 1-95 corridor, as of 2005.

The organization recently released images that illustrate the change in concentration of nitrogen oxide, a pollutant that's linked to adverse effects on the respiratory system.

"Nitrogen dioxide is one of the six common pollutants regulated by the U.S. Environmental Protection Agency (EPA) to protect human health. Alone it can impact the respiratory system, but it also contributes to the formation of other pollutants including ground-level ozone and particulates, which also carry adverse health effects. The gas is produced primarily during the combustion of gasoline in vehicle engines and coal in power plants. It's also a good proxy for the presence of air pollution in general."

According to NASA, Philadelphia also experienced a 26 percent decrease in nitrogen dioxide between the periods of 2005-2007 and 2009-2011. A similar decline was also seen in western parts of the United States.

Researchers noted that the reason for decreased rates of air pollution was primarily due to better regulations, technological improvements and economic shifts, despite increasing populations and the use of motor vehicles.

"While our air quality has certainly improved over the last few decades, there is still work to do - ozone and particulate matter are still problems," said Bryan Duncan, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, according to The Washington Post.