5 Greenest Small Towns in America

3. Koloa, Hawaii

Average PM2.5 Concentration (2023): 2.2 µg/m³

Koloa is a census-designated place and an unincorporated community in Hawaii. Its major air pollutant is fine particulate matter. In 2023, Koloa had an average fine particulate matter concentration of 2.2 micrograms per cubic meter, which is in line with the WHO standard for air quality. It is the 3rd greenest small town in America.