Home » Air » Few Unhealthy Air Days in Missouri Counties in 2017

Few Unhealthy Air Days in Missouri Counties in 2017


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. In the previous post, I reported on the percentage of days during which air quality was in the good range in 24 Missouri counties. This post focuses on the percentage of days with unhealthy air quality.

I looked at data from the EPA’s Air Quality Index Report for 24 Missouri counties. The data covered the years 2003-2017, plus the years 1983 and 1993 for a longer term perspective. For a fuller discussion of air quality and the data used for this post, and a map of the 24 counties, see my post Air Quality Update, 2017.

Figure 1. Data source: Environmental Protection Agency.

The EPA data distinguishes 4 levels of unhealthy air: Unhealthy for Sensitive Individuals, Unhealthy, Very Unhealthy, and Hazardous. No Missouri county was reported to have Very Unhealthy or Hazardous air quality for any of the years I studied. Figure 1 shows the percentage of monitored days for which air quality was either Unhealthy for Sensitive Individuals, or Unhealthy. The top chart shows a group of counties along the Mississippi River north or south of St. Louis. The middle chart shows a group of counties in the Kansas City-St. Joseph region. The bottom chart shows a group of widely dispersed counties outside of the other two areas. For the locations of the counties, see here.

(Click on chart for larger view).

The percentage of unhealthy air days was 1% or below for all Missouri counties . There were no unhealthy air days at all in 13 of the 24 counties, and no county had more than 4 unhealthy AQI days. Compared to 2016, 4 counties showed very small increases, and 9 had decreases. Compared to 1983, the total number of unhealthy air days across all counties decreased from 490 to 21, a 96% decline. St. Louis City, St. Louis County, Iron County, Jackson County, and Jackson County, in that order, were the counties in 1983 with the highest number of unhealthy air days. By 2017, those four counties had decreased the number of unhealthy air days by 98%, 99%, 97%, 100%, and 100%, respectively.

Well done! We have more work to do before all Missourians can breath truly good quality air every day, but the decrease in unhealthy days is amazing, just amazing. In the next post, I will discuss the most important air pollutants in Missouri. After that, I will discuss the health effects of air pollution, and you will understand why the reduction in unhealthy air days is such an important achievement.


Environmental Protection Agency. Air Quality Index Report. This is a data portal operated by the EPA. Data downloaded on 7/31/2018 from http://www.epa.gov/airdata/ad_rep_aqi.html.

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