With air pollution, averages don’t tell us a whole lot. We need to look at specific locations to see if air quality is really improving. Let’s examine Chicago (Cook County). As the center of a big ‘ol historical industrial area, you’d expect Chicago to have some of the worst air in the country.
|Number of Days when Air Quality was…|
|Unhealthy for Sensitive Groups||22||23|
|Number of Days When Main Pollutant Was:|
|PM 2.5: Particulate matter < 2.5 micrometers||147||222|
|PM 10: Particulate matter < 10 micrometers||43||22|
You can probably spin these numbers however you like. On the surface, Chicago had fewer Good days and more Unhealthy days in 2007 than 1998. The primary cause would seem to be more days with lots of Small Particulates (< 2.5) in the air. On the other hand, there were half as many days with large particulates (the < 10 micrometers kind that you can choke on) and far fewer days where Sulfur Dioxide or Carbon Monoxide were the primary pollutant. Of course, it makes you wonder how much of those particulates come from chocolate?
FWIW, in 2007 Chicago had the sixteenth worst air in the United States.
Number of Days when Air Quality was…