Striking new images released by NASA this week show significant reductions in air pollution levels across the United States. In particular, at least one pollutant, nitrogen dioxide, has decreased substantially over the past decade.

After ten years in orbit, the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite showed that the decrease is particularly prominent in the Northeast, the Ohio River Valley, and other major cities. For example, NASA reported a 32% decrease in New York City and a 42% decrease in Atlanta between the periods of 2005-2007 and 2009-2011.

Air pollution decreased even though population and the number of cars on the roads have increased, and the shift can be explained as a result of better regulations, technological improvements and economic shifts, scientists said.

“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, Md.

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