WMUR: The air we breathe in the United States is getting better -- at least by one recent measure. New data released by NASA this week show that at least one pollutant, nitrogen dioxide, has decreased substantially over the past decade. Areas with a high level of nitrogen dioxide have decreased an average of about 40 percent, said Bryan Duncan, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It happened everywhere, not just in a few areas. It's over the whole...