2. Farmington, New Mexico, USA
PM 2.5 annual mean, ug/m3: 3.70
While Farmington, New Mexico, enjoys the cleanest air in the country, not far from this city Navajo communities are plagued by pollutants because of the San Juan Generating Station (coal plant). According to ALA report, Farmington tied the number one spot with Cheyenne, Wyoming, as the city with the cleanest air in the U.S. Cities were ranked according to annual particle pollution (PM 2.5).