Yosemite Park webcams paint a bleak air quality picture on Tuesday morning as the Meadow Fire continues to burn in Little Yosemite Valley.
NASA has released some encouraging images showing a marked decline in air pollution over much of the eastern U.S.
Since Monday, parts of Maryland and northwest Virginia have experienced compromised air quality in the code orange range.
One of the worst U.S. air pollution episodes was the choking, deadly smog that covered Donora, Pa., in October 1948, killing 20 people and leaving roughly 7,000 ill in hospitals or at home.
The northern Chinese city of Harbin was effectively shut down Monday after suffocating in a dense soup of pollution.
The hot, stagnant air over the Washington, D.C. area has prompted the first air quality alert of 2013.