NEW YORK (CNN) – NASA satellite data show that, at least by one measure, air pollution has decreased recently.
Over the last decade, nitrogen dioxide has decreased in cities across the U.S. Especially along the densely-populated I-95 corridor in the northeast, the difference is striking.
“This represents a map in 2005, of nitrogen dioxide, and you can tell by the red that pollutant levels are high, all along the eastern seaboard. The Ohio river valley, the major cities of the US like Atlanta, and Chicago,” said NASA Atmospheric Scientist Bryan Duncan.
What do we have now?
“Now we have much lower levels, of this one pollutant, levels have gone down by about 40%, since 2005,” said Duncan.
Nitrogen dioxide is yellow-brown smog that comes mostly from vehicles, and coal-burning power plants. It forms ozone, the gas in the atmosphere that burns our lungs.
So why is the air getting better, even though the number of cars on the road has increased?
“Our pollutant levels are going down, and that’s because cars are becoming more fuel-efficient,” said Duncan.
Newer coal-burning power plants now scrub much of the pollution out before it can get to our lungs.
The world health organization says in 2012, about 3.7-million people around the world died from the effects of outdoor air-pollution, most of them in Asia.
Experts say the people who smog has hit the hardest are the ones who can really feel this improvement in our air.
“People who have asthma, they definitely can tell that they’re breathing easier. And it’s easier when we’re looking at it on a long-term basis or looking at hospital records or other medical records,” said Janice E. Nolen of the American Lung Association.
Nitrogen dioxide levels are also a good indicator of how other pollution is trending. Experts say it’s not all good news. There are other pollutants causing harm.
“We have about half the nation who lives in counties that have unhealthy levels of air-pollution,” said Nolen.
That’s more than 140-million Americans who still live in areas that have unhealthy air.
The worst city in the country for ozone pollution: Los Angeles, even though that city has made big improvements. The American Lung Association says L.A. has cut its pollution by about a third over the past 15 years.