Air Quality in the United States by Michael Mixon

The Environmental Protection Agency (EPA) takes hourly Air Quality readings at hundreds of sites nationwide, and produces an Air Quality Index (AQI) that measures how healthy the air is at different locations based on the presence of certain pollutants such as ozone.

The AQI has five levels:

● Very Unhealthy ( AQI >.105)

● Unhealthy (AQI <=.105)

● Unhealthy for Sensitive Groups (AQI <=.085)

● Moderate (>AQI <=.07)

● Good (AQI <=.054)

For this analysis, a daily average AQI was taken for each day over the last 20 years. If that AQI did not fall below .054 parts per million (ppm), it is considered a "not good" day. All of those "not good" days were then compared to all daily measurements taken in each county to determine the % of bad days a particular county experienced by year and season.

That percentage is reflected in the chart to the left.