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Fewer Unhealthy Air Days


Unhealthy Mississippi ChartIn my previous two posts, I have discussed the air quality data maintained in the EPA’s Air Quality System Data Mart, and I have reported on the number of days with good air quality. It is one thing to ask whether a county’s air quality is good, and another to ask if it is so bad that it is unhealthy. This post focuses on the number of days with unhealthy air.

I downloaded data going back 10 years (2012-1993), and for a longer term perspective, for 1993 and 1983. Nineteen Missouri counties have been monitored for more than 6 of those 12 years. I put them in three groups: a group along the Mississippi River north and south of St. Louis, a group in the Kansas City-St. Joseph region, and a widely dispersed “other” group.

The EPA data distinguishes four levels of unhealthy air: Unhealthy for Sensitive Individuals, Unhealthy, Very Unhealthy, and Hazardous. No Missouri county is reported to have Very Unhealthy or Hazardous air quality for any of the years I studied. The graphs on the right show the percent of monitored days for which air quality was either Unhealthy for Sensitivie Individuals, or Unhealthy.

Unhealth KC ChartThe top graph is for counties along the Mississippi. It shows that since 1983, there are far fewer unhealthy air days. The lone exception is for Jefferson County, where the number of unhealthy air days has increased: there, the number of unhealthy air quality days runs somewhere between 1 in 6 and 1 in 4. In all counties the number ticked up in 2012.

The second graph is for counties in the Kansas City-St. Joseph area. As we saw in the graphs for good air quality (previous post), the region started off with better air than did the Mississippi counties. Jackson County started with zero days of unhealthy air in 1983, and less than 2% in 1993. This seems to be an unusual finding, and one wonders if it is an error. The overall trend here seems to be flat, although the counties tend to show the same uptick in 2012 as the counties along the Mississippi.

The third graph is for Other counties. Iron County had a significant number of unhealthy air days in 1983-2003. After that, however, the number of unhealthy air quality days plummeted, I don’t know why. For all of the counties, the percentage of unhealthy air days is quite low, although it upticked slightly in 2012.

Unhealthy Outstate ChartThe uptick seen in 2012 for virtually all counties is probably related to the drought and record heat experienced around the state in that year. (See here for my post on it.)

I started this series of posts remembering The Day the Sun Didn’t Shine, November 28, 1939 in St. Louis. Compared to that, our air quality has clearly improved. Even since 1983, the number of unhealthy air days seems to have significantly decreased. However, the trend with good air quality days is not so marked. A significant portion of the state, especially in the large metropolitan areas, is still breathing air that is less than good on 3-5 out of every 10 monitored days.

Added 10/30/13:

Since posting the above, I have discovered that the Department of Natural Resources operated an air pollution monitoring site in Glover, MO. In 2003, the Glover Lead Smelter closed, and perhaps this accounts for the sudden improvement in sulfur dioxide levels in Iron County.


Air Data, EPA, http://www.epa.gov/airquality/airdata.

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