Air quality in 13 out of 20 counties in Missouri improved in 2016 compared to 2014, while air quality in 7 declined. The data come from the Air Quality System Data Mart maintained by the EPA , which contains data on the air quality of a number of Missouri counties going back to the early 1980s. For a fuller discussion of air quality and the data maintained by the EPA, or for a map of the counties, see my previous post.
Figures 1 shows the percent of monitored days on which the Air Quality Index was in the Good Range. The top chart is for a group of counties along the Mississippi River, the middle chart is for a group of counties in the Kansas City-St. Joseph region, and the bottom chart is for a widely scattered group of counties in neither of the other two groups.
(Click on chart for larger view.)
First, compared to 2014, the percentage of good air days increased in 13 out of the 20 counties. Most of the increases were small, but the percentage of good AQI days jumped by 31% in Cass County, by 28% in the Jackson County, by 19% in Buchanan County, and by 16% in the City of St. Louis. The increase in Jackson County is especially notable, as their trend had not been toward significant improvement for several years. It is hard to achieve a very high percentage of good AQI days in large cities, and both Jackson County and the City of St. Louis have made significant progress over the years.
The percentage of good AQI days fell in 7 counties. In three of them, the decline was greater than 10%: Stoddard County (-13%), Clinton County (-12%), and Perry County (-12%).
While the overall trend in 2016 was favorable compared to 2014, local factors seem to have controlled the variation between counties. The overall trend may not be attributable to weather, as it was almost 3°F warmer in 2016 than in 2014.
Second, in almost all Missouri counties the percentage of good air quality days was high in 2016. In no county was it below 60%, and it was 80% or above in 16 out of the 20 counties. As in previous years, the outstate group led in the percentage of good AQI days, which is expected because they don’t experience the concentration of pollution sources that large cities do.
In 2016, Stoddard County and the City of St. Louis tied for the lowest percentage of good air days of any county in Missouri: 64%. For Stoddard County, this represents a significant decline: they had 91% good AQI days in 2015. For the City of St. Louis, however, it represents a continuing trend of improvement from very poor AQI. St. Louis still has plenty of air quality challenges, but we’ve come a long way, baby!
Over a longer term, the chart for the Mississippi counties is encouraging. The lines start pretty low for some of the counties, but have a clear upward trend. The chart for the Other counties is also encouraging. The lines start pretty high, most had an upward trend for a number of years, and in recent years most seem to be staying high. The chart for the Kansas City-St. Joseph counties is more variable, showing yearly ups and downs. When I looked at the 2014 data, the air quality in most of the Kansas City-St. Joseph counties had declined since 1983. In 2016, that trend has largely been reversed.
Environmental Protection Agency. Air Quality Index Report. This is a data portal operated by the EPA. Data downloaded 3/23/2017 from http://www.epa.gov/airdata/ad_rep_aqi.html.