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.
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