Air Quality Index – AQI (Average for 2021): 43 – Good (IQ Air – USA)
- Global ranking (Average Pollution 2021): #29 least polluted nation, out of 118 monitored. (IQ Air – USA)
- Most polluted city (2021 average): Weaverville, CA | AQI = 98 – Unhealthy for Sensitive Groups (IQ Air – USA).
- Least polluted city (2021 average): Neah Bay, WA | AQI = 13 – Very Good (IQ Air – USA).
- The Los Angeles area and region have the most consistent highest level of air pollution in the US, followed by San Francisco area, Houston, TX, and Phoenix, AZ. (American Lung Association)
- Cheyenne, WY, and Wilmington, NC, have the consistent lowest level of air pollution of cities in the US. (American Lung Association)
- About 24 million Americans (7.1% of residents) live in areas with unhealthy air pollution. (American Lung Association)
- Fossil fuel combustion, primarily from transportation, industrial activities, and power production, is the leading cause of US air pollution. It accounts for one-third of all pollution in the US. (EPA)
- Since the US passed The Clean Air Act in 1990, air quality has dramatically improved with the EPA estimating over 230,000 deaths due to air pollution were prevented by 2020.
- US National Park Service and US Forest Service scientists use lichens as a biomonitor to assess air quality across the country.