15 Cities With the Biggest Improvement in Air Quality During COVID-19

Editor's Note: This story originally appeared on Filterbuy.

While public attention on the environment has recently focused on the acceleration of global climate change, another important and closely related issue is air quality. Climate change and air pollution share many of the same causes, with reliance on fossil fuels for energy and transportation being a major contributor to both.

And the two phenomena also impact and reinforce each other: Climate-driven events like wildfires can increase the volume of air pollutants including particulate matter, while the emission of pollutants like ozone increases the atmosphere’s capacity to retain heat.

Recent evidence suggests that COVID-19 shutdowns in 2020 had a positive but short-lived effect on air quality. When large parts of economic and social life worldwide halted at the beginning of the pandemic, there was a sharp drop-off in major sources of pollution like industrial production and vehicle usage. This meant that the atmosphere saw a temporary reduction in emissions of pollutants.

To determine the locations with the biggest improvement in air quality during COVID-19, researchers at Filterbuy used data from the U.S. Environmental Protection Agency to calculate the percentage change in median AQI (Air Quality Index) from 2019 to 2020. Locations with the larger decrease in median AQI were ranked higher. You can read more about our methodology at the end.

Following are the cities with the biggest improvement in air quality during 2020.

15. Milwaukee-Waukesha-West Allis, WI

Percentage change in median AQI (2019-2020): -6.8%

Median AQI (2020): 41

Median AQI (2019): 44

Percentage of days with good air quality (2020): 69.1%

Percentage of days with good air quality (2019): 69.6%

14. Cincinnati, OH-KY-IN

Percentage change in median AQI (2019-2020): -7.4%

Median AQI (2020): 50

Median AQI (2019): 54

Percentage of days with good air quality (2020): 53.0%

Percentage of days with good air quality (2019): 38.1%

13. New York-Newark-Jersey City, NY-NJ-PA

Percentage change in median AQI (2019-2020): -7.8%

Median AQI (2020): 47

Median AQI (2019): 51

Percentage of days with good air quality (2020): 60.4%

Percentage of days with good air quality (2019): 46.3%

12. Washington-Arlington-Alexandria, DC-VA-MD-WV

Percentage change in median AQI (2019-2020): -8.5%

Median AQI (2020): 43

Median AQI (2019): 47

Percentage of days with good air quality (2020): 77.9%

Percentage of days with good air quality (2019): 57.3%

11. Baltimore-Columbia-Towson, MD

Percentage change in median AQI (2019-2020): -8.7%

Median AQI (2020): 42

Median AQI (2019): 46

Percentage of days with good air quality (2020): 78.1%

Percentage of days with good air quality (2019): 61.1%

10. Indianapolis-Carmel-Anderson, IN

Percentage change in median AQI (2019-2020): -9.3%

Median AQI (2020): 49

Median AQI (2019): 54

Percentage of days with good air quality (2020): 51.9%

Percentage of days with good air quality (2019): 40.5%

9. Birmingham-Hoover, AL

Percentage change in median AQI (2019-2020): -9.4%

Median AQI (2020): 48

Median AQI (2019): 53

Percentage of days with good air quality (2020): 56.8%

Percentage of days with good air quality (2019): 41.1%

8. Detroit-Warren-Dearborn, MI

Percentage change in median AQI (2019-2020): -10.7%

Median AQI (2020): 50

Median AQI (2019): 56

Percentage of days with good air quality (2020): 51.4%

Percentage of days with good air quality (2019): 37.0%

7. Columbus, OH

Percentage change in median AQI (2019-2020): -10.9%

Median AQI (2020): 41

Median AQI (2019): 46

Percentage of days with good air quality (2020): 79.8%

Percentage of days with good air quality (2019): 64.9%

6. Pittsburgh, PA

Percentage change in median AQI (2019-2020): -12.5%

Median AQI (2020): 49

Median AQI (2019): 56

Percentage of days with good air quality (2020): 53.8%

Percentage of days with good air quality (2019): 35.3%

5. Raleigh, NC

Percentage change in median AQI (2019-2020): -13.0%

Median AQI (2020): 40

Median AQI (2019): 46

Percentage of days with good air quality (2020): 77.5%

Percentage of days with good air quality (2019): 65.5%

4. Richmond, VA

Percentage change in median AQI (2019-2020): -13.6%

Median AQI (2020): 38

Median AQI (2019): 44

Percentage of days with good air quality (2020): 89.9%

Percentage of days with good air quality (2019): 74.5%

3. Charlotte-Concord-Gastonia, NC-SC

Percentage change in median AQI (2019-2020): -14.3%

Median AQI (2020): 42

Median AQI (2019): 49

Percentage of days with good air quality (2020): 77.0%

Percentage of days with good air quality (2019): 54.8%

2. Virginia Beach-Norfolk-Newport News, VA-NC

Percentage change in median AQI (2019-2020): -15.0%

Median AQI (2020): 34

Median AQI (2019): 40

Percentage of days with good air quality (2020): 94.8%

Percentage of days with good air quality (2019): 86.8%

1. Atlanta-Sandy Springs-Roswell, GA

Percentage change in median AQI (2019-2020): -15.4%

Median AQI (2020): 44

Median AQI (2019): 52

Percentage of days with good air quality (2020): 65.8%

Percentage of days with good air quality (2019): 44.4%

Methodology

The data used in this analysis is from the U.S. Environmental Protection Agency’s Air Data report. To determine the locations with the biggest improvement in air quality during COVID, researchers calculated the percentage change in median Air Quality Index values from 2019 to 2020.

Locations with the larger decrease in median AQI were ranked higher. In the event of a tie, the median AQI for 2020 and 2019 were used, with lower values being ranked higher. Researchers also calculated the percentage of days each year in which the air quality was considered to be good, defined as having an AQI below 50.