Which US City Has the Cleanest Air?

Cheyenne, Wyoming is the US city that has the cleanest air, according to findings from the American Lung Association. The city of less than 89,000 people has the lowest particulate matter (PM 2.5) rating, which refers to fine matter in the air that has a diameter of less than 2.5 micrometers. PM 2.5 ratings are important for measuring air quality because particulate matter that small can be absorbed into the lungs. Cheyenne also has the lowest levels of short-term peaks in pollution exposure, which can cause asthma and heart attacks. The city’s small population is thought to contribute to its clean air due to less vehicle pollution.

More about air quality throughout the world:

• Particulate matter that is less than 2.5 micrometers is approximately 1/30th the width of a human hair.
• Nearly half of the US population, or over 147 million people, is estimated to live in areas with potentially hazard levels of air pollution.
• Tasmania is thought to have the cleanest air in the world, with quality levels on part with the unpopulated Antarctica.