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The Most Important Pollutants in 2014

In my previous 3 posts, I have noted that in most Missouri counties air quality improved from 2013 to 2014: the percentage of unhealthy air quality days decreased, and the percentage of good air quality days increased. However, the Air Quality Index is a measure that combines the level of pollution from six criterion pollutants: ozone (O3), sulphur dioxide (SO2), nitrous oxide (NO2), carbon monoxide (CO), particulate matter smaller than 2.5 micrometers (PM2.5), and particulate matter between 2.5 and 10 micrometers (PM10). For a brief discussion of these pollutants, see Air Quality Update 2014.

Data source: Environmental Protection Agency Air Quality Index Report

Data source: Environmental Protection Agency Air Quality Index Report

The chart at right shows the percentage of days for which each of the criterion pollutants was the most important one. The chart combines all 20 counties together. In 2014, as in 2013, ozone was the most important pollutant, followed by small particles (PM2.5). One or the other of these two pollutants was the most important on 87% of all days statewide.

Thirty years ago, ozone was a much less important pollutant than it is now. In 1983, it was the most important pollutant on fewer than 30% of the days statewide. It is now the most important pollutant on about half the time (49% in 2014, 51% in 2013). While we need ozone in the upper atmosphere to shield us from ultraviolet radiation, at ground level it is a strongly corrosive gas that is harmful to plants and animals (including us humans). We don’t emit it directly into the air. Rather, it is created when nitrogen oxides and volatile organic compounds (think vapor from gasoline and other similar liquids) react in the presence of sunlight. These pollutants are emitted into the atmosphere by industrial facilities, electric power plants, and motor vehicles.

The second most important pollutant was PM2.5 (38% of the time in 2014, 35% in 2013). These tiny particles were not recognized as dangerous until relatively recently, though now they are thought to be the most deadly form of air pollution. I can’t find anything that says so specifically, but I believe their zero readings in 1983 and 1993 means that PM2.5 wasn’t being measured in Missouri, not that it wasn’t a significant pollutant back then. The EPA significantly tightened its regulations for PM2.5 a couple of years ago, and the Missouri Department of Natural Resources is in the midst of deploying a program to come into compliance with the new standards. Road vehicles, industrial emissions, power plants, and fires are important sources of PM2.5.

Sulphur dioxide used to be by far the most important pollutant. While it has not been eliminated and was still the most important pollutant on some days, good progress has been made on reducing SO2 emissions (48% of the time in 1983, 8% in 2014). For the role of SO2 in background air pollution, see this post.

In Jackson County, the county with more unhealthy air days than any other, the most important pollutant in 2014 was PM2.5. It was most important on 200 days, while sulphur dioxide was most important on 97. In St. Louis City, the county with the second most unhealthy air days, the most important pollutant was also PM2.5. It was most important on 251 days, while ozone was most important on 54.

Don’t forget that the chart at right does not show the levels of the six pollutants, it only shows the number of days on which each was the most important. As previous posts have clearly shown, air quality is better. As we have reduced some types of air pollution, apparently, other types have become more important.

I’ll offer some summary conclusions about this air quality data and climb on my soapbox briefly in the next post.

Sources:

Environmental Protection Agency. Air Quality Index Report. This is a data portal operated by the EPA. Data for 2014, Missouri, and grouped by County downloaded on 11/6/2015 from http://www.epa.gov/airdata/ad_rep_aqi.html.

Few Unhealthy Air Days in Most Counties

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

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. The previous post focused on good air quality days. This post focuses on the percentage of days with unhealthy air quality.

I looked at data from the EPA’s Air Quality System Data Mart for 20 Missouri counties. The data covered the years 2003-2014, 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 20 counties, see my post Air Quality Update 2014.

The EPA data distinguishes 4 levels of unhealthy air: Unhealthy for Sensitive Individuals, Unhealthy, Very Unhealthy, and Hazardous.

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

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 Sensitive Individuals, or Unhealthy. The first chart shows a group of counties along the Mississippi River north or south of St. Louis. The second chart shows a group of counties in the Kansas City-St. Joseph region. The third chart shows a group of widely dispersed counties outside of the other two areas.

(Click on chart for larger view).

The percentage of unhealthy air days was 2% or below for all Missouri counties except one: Jackson County (the location of Kansas City). There were no unhealthy air days at all in 15 of the 20 counties.

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

The percentage of unhealthy air quality days increased in only two counties: Jackson County and the City of St. Louis.

The percentage of unhealthy air quality days was 14% in Jackson County, making it by far the worst performer in the state. No other county had more than 2%. This is the second year in a row that Jackson County has had the most unhealthy air days, and since 2011 the trend has been upward.

It is heartening, and good for the lungs too, that only one county in Missouri had a significant fraction of days on which the air quality was unhealthy. The state clearly has improved its air quality. It is equally clear, however, that in Missouri’s two largest metropolitan areas, air quality is not yet good on the majority of days.

Sources:

Environmental Protection Agency. Air Quality Index Report. This is a data portal operated by the EPA. Data for 2014, Missouri, and grouped by County downloaded on 11/6/2015 from http://www.epa.gov/airdata/ad_rep_aqi.html.

2014 Air Quality Improved in Some Counties

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

Air quality in 12 of 20 counties in Missouri improved in 2014 compared to 2013, while air quality in 5 declined, and air quality in 3 counties was unchanged. 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.

The graphs at right show the percent of monitored days on which the Air Quality Index was in the Good Range. The top graph is for a group of counties along the Mississippi River, the middle one is for a group of counties in the Kansas City-St. Joseph region, and the bottom one is for a widely scattered group of counties in neither of the other two groups.

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

First, the percentage of good air days increased in 12 out of the 20 counties. Most of the improvements were small, but the percentage of good air days increased 14% in Jefferson County, 8% in Clinton County, and 7% in Iron County.

On the other hand, 5 counties experienced a lower percentage of good air days. In Cass County the percentage of good air days decreased by 18%, and in Stoddard County, it decreased by 15%.

The results are variable across counties and across regions. Thus, I suspect that the causes may relate to local factors in each county. For instance, the results in Jefferson County may relate to the closure of the Doe Run lead smelter.

I suspect that both electricity consumption and vehicle miles driven increased in Missouri during 2014, however data is not yet available, so I can’t test my hunch. Both contribute to poor air quality, so if they did increase, then the improvement in air quality in the majority of counties would be all the more impressive.

Data source: Environmental Protection Agency

Data source: Environmental Protection Agency

Second, in some Missouri counties the percentage of good air quality days was quite high in 2014. In the Mississippi River group, Lincoln and Perry Counties tied for the highest percentage of good air days, with 93%. In the Kansas City-St. Joseph group, it was Clinton County with 94%. In the Other group, Monroe, Iron, Boone, and Taney Counties all had good air day percentages at or above 95%.

Third, as in 2013, the City of St. Louis had the lowest percentage of good air days of any county in Missouri: 48%. That should be no surprise given its history in the annals of air pollution (see previous post). Fewer than half of the measured days in St. Louis City had good air quality, and the fact that the number did not improve is troubling. The only other county giving St. Louis a contest for lowest percentage of good air days was Jackson County, the location of Kansas City, with 52%.

Over a longer term, the chart for the Mississippi counties is somewhat encouraging. The lines start pretty low for some of those counties, but have a clear upward trend. The chart for the Other counties is also encouraging. The lines start pretty high, and most have an upward trend. The chart for the Kansas City-St. Joseph counties is more equivocal, however. Air quality in most of these counties has declined since 1983. Some appear to have begun to recover, but only Clinton County has air quality equal to or better than in 1983.

Source:

Environmental Protection Agency. Air Quality Index Report. This is a data portal operated by the EPA. Data for 2014, Missouri, and grouped by County downloaded on 11/6/2015 from http://www.epa.gov/airdata/ad_rep_aqi.html.

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