Interesting things found in data:
In my studies of the air quality data, I found that in my particular area, air quality has improved over the years. I live in Cook county in the state of Illinois. The trend that I see in my area is that there are far more Good Days of AQI in 2018 than there was in 1980.
I also observed a few other states and counties throughout the US that had a similar trend. If one observes New York's AQI in 1980 and 2018, one would see that the AQI has improved significantly.
Are we doing better?
It's complicated. Although air quality is going up in these major cities, the pollutants have just been replaced by different ones since 1980. I observed that the Ozone pollutant is increasing in both Illinois (near Chicago) and New York (New York). The natural trend in these two major cities is that Ozone and PM2.5 has increased significantly since 1980. Although other pollutants such as CO, NO2 and SO2 have gone down, Ozone and PM2.5 have drastically increased.
Are there places that are more or less polluted than you expected?
Yes, I was expecting Denver Colorado to have some of the best AQI in the country in 1980. So I was surprised to see that the AQI in Denver was actually worst in 1980 than 2018. When one observes the data, one sees that carbon monoxide pollution was very high in that time. I assumed that the trees and mountains will produce some of the highest quality air in the country; especially back in that time. So I was surprised to see very poor AQI. Perhaps it was due to the burning of wood at that time.
What trends do you see in terms of where the most and least polluted areas are?
The trend that I was expecting was worst air quality near the big cities in the US. What I ended up discovering was that living near a big city did not necessarily determine increased AQI. Living in areas with lots of forests did not necessarily give you better AQI.
I also observed that the natural trend for most of the counties was increased AQI since 1980. Most counties have far more Good AQI today than they did back in 1980.
Cook County Illinois AQI 1980
Cook County Illinois AQI 2018