Ups and downs in the quest for clean air
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2014/08/maps001-1.png?fit=860%2C460&ssl=1)
BREATHING EASIER Newly released maps reveal that U.S. air quality has markedly improved over the last decade.
NASA Goddard Scientific Visualization Studio
BREATHING EASIER Newly released maps reveal that U.S. air quality has markedly improved over the last decade.
NASA Goddard Scientific Visualization Studio