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Air Quality in Indiana

Air Quality in Indiana > Air Quality 101 > March 2014: Is Indiana’s Air Quality Getting Worse? March 2014: Is Indiana’s Air Quality Getting Worse?

Every quarter, we evaluate what percent of Hoosiers live in areas that have clean air quality. In essence, this means areas that are meeting the national ambient air quality standards (NAAQS) established by US EPA. Recently our percentage went from the mid 90’s to about 87 percent. This would appear to indicate that our air quality is getting worse. However, this is not the case. Air quality is the cleanest it has been since the 1970s, when states began monitoring for the six criteria air pollutants. At the same time, revisions have been made to the national air health standards over the years, to further reduce pollutants in the ambient air.

An example is when U.S. EPA established a more stringent sulfur dioxide standard with a 1-hour averaging period. Data showed parts of five Indiana counties did not meet this standard. This led to the impression that there was an increase in the number of people exposed to unhealthy air. Air is cleaner than it was before, but now does not meet a new standard. Think of having a road that does not have a speed limit. Then a 35 mile per hour speed limit is established. Several speeding tickets are issued. The perception is that people are driving faster. However, this may not be the case. Now there is a speed limit where before there was none. This is the same situation with the air quality. Before there was no 1-hour sulfur dioxide standard and then there was. Below we will look at levels in each of the five areas and determine whether things are getting better or worse.

The 1-hour sulfur dioxide standard works as follows. A level is measured for each hour. If any hour within a day exceeds 75 parts per billion, then the day has exceeded the standard. If four or more days exceed the standard in a year, the area has violated the standard. Officially the status of an area is based on the average of the most recent three years. For this analysis, I will only show annual values.

Daviess County

The most recent year of data is 2013. In that year there were 18 days that had hours exceeding the 1-hour standard. This is down from the maximum of 37 days measured in 2000. The maximum hourly value measured in 2013 was 202 parts per billion (ppb). This is down from the maximum of 241 ppb measured in 2008.

Marion County

In 2013 there were six days that had hours exceeding the 1-hour standard. This is down from the maximum of 30 days measured in 2005. The maximum hourly value measured in 2013 was 113 ppb. This is down from the maximum of 228 ppb measured in 2003.

Morgan County

In 2013 there were two days that had hours exceeding the 1-hour standard. This is down from the maximum of 28 days measured in 2005. The maximum hourly reading measured in 2013 was 122 ppb. This is down from the maximum of 196 ppb measured in 2007.

Pike County

In 2013 there were 20 days that had hours exceeding the 1-hour standard. This is down from the maximum of 56 days measured in 2008. The maximum hourly reading measured in 2013 was 293 ppb. This is down from the maximum of 337 ppb measured in 2003.

Vigo County

In 2013 there were 16 days that had hours exceeding the 1-hour standard. This is down from the maximum of 43 days measured in 2008. The maximum hourly reading measured in 2013 was 151 ppb. This is down from the maximum of 499 ppb measured in 2001.

While all of these areas have shown improvement, each area is required to achieve the standard of 75 ppb. Coal-powered electric generating plants are the highest emitters of sulfur dioxide, and IDEM is working now to ensure they will meet new limits. In the meantime utilities will be closing units, switching fuels, adding controls or upgrading controls to achieve the necessary emission reductions.

Comments can be sent to me at kbaugues@idem.in.gov.