The Environmental Protection Agency is embroiled in a political debate over whether it should regulate greenhouse gases—and by how much. We’ve had debates like this before on other pollutants, so it’s worth examining how successful the EPA has been in the past.
Thanks to some new maps from NASA, we can do just that.
The images, based on data collected by NASA’s Aura satellite, show how air quality has improved as the pollutant nitrogen dioxide (NO2) declined in the U.S. Nitrogen dioxide is an ugly yellowish-brown gas that harms the lungs and is a good proxy for air pollution, generally. It comes from car and truck engines, as well as power plants.
The areas of red and orange on the map below, signifying higher concentrations of the air pollutant, shrank substantially between 2005 and 2011:
NASA Goddard's Scientific Visualization Studio/T. Schindler
As you can see, the most-populated East Coast cities have been the seen the biggest drop. New York, for example, saw a decrease of 32 percent over the period:
NASA Goddard's Scientific Visualization Studio/T. Schindler
The EPA has long regulated this pollutant under the Clean Air Act, along with ozone, lead, carbon monoxide, sulfur oxides, and particulate matter. But the EPA has strengthened its rules for nitrogen dioxide over time, plus it phased in new vehicle standards over a period between 2004 and 2010. That explains the progress.
Even with the improvement, about half the country’s population still live in areas that have what the American Lung Association says is unhealthy air. So while there has been a lot of progress in the last 40-plus years of the Clean Air Act, there is more the EPA can do to keep polluting sources in check. And it is already doing so. A study from the Harvard Public School of Health found that the EPA’s proposed rule to control carbon pollution from coal-fired power plants is expected to cut lung and heart-damaging pollutants even more.