Air quality in the U.S. has made a lot of progress since the lung-destroying days of the 1940s, but a lot remains to be done. The World Health Organization has categorized air pollution in the same category as tobacco smoke, UV radiation and plutonium, and considers it the world’s biggest environmental health risk with 7 million deaths per year, more than AIDS and malaria combined. In urban areas around the world, 7 out of 8 people aren't breathing air that the WHO would consider safe. Just in the U.S., about 142 million people still lived in areas with unhealthy levels of air pollution, according to the EPA.
But enough bad news. Back to the positive: NASA has been monitoring nitrogen dioxide levels over the U.S. using the Aura satellite. Starting in 2005, they've been gathering data that shows a clear trend, especially in urban areas; pollution has been decreasing despite the fact that the number of cars on the road has been increasing. We can thank better technology and regulations for these improvements. The change is clearly visible on the animated map below:
Here's a closeup of some of the most important urban areas in the country:
Above is the New York area, where you can see that things have improved a lot - at least as far as NOx are concerned - since the 2005-2007 period (left) and the 2009-2011 period (right), with a 32% decrease in NOx.
Atlanta has improved significantly as well, with a 4% decrease in nitrogen dioxide concentrations.
Here's Chicago with a 43% improvement overall.
The Philadelphia area, with a 26% improvement over a very large area (part of the Eastern Seaboard's "river of pollution").
Los Angeles and San Diego with an impressive 40% improvement. And that's even after Los Angeles had improved significantly in past decades compared to what it used to be.
Next is Houston, with a 24% improvement.
Even Denver, which used to be a small island of polluted air in a sea of clean air, has improved significantly with a 22% decrease in NOx.
So I'm curious to know, has the air quality been improving where you live?
NASA has created this video about the importance of air quality and the Aura mission: