October 2013: The Percent of Hoosiers Breathing Clean Air

This is the seventeenth article in a series about air quality in general and how it applies to Indiana. This article will discuss the percent of Hoosiers breathing clean air.

Every quarter the Office of Air Quality (OAQ) submits a report to the Governor’s office that includes a metric called percent of Hoosiers breathing clean air. Recently this value has taken a downturn and I would like to explain why. This metric covers the percent of Hoosiers that are breathing air that meets the national ambient air quality standards (NAAQS). About four years ago it was 100%. The United States Environmental Protection Agency (U.S. EPA) then changed the standard for lead, lowering the allowable level by a factor of 10. We had one area of the state that did not meet this new standard. The area was very small and the number of people possibly included was 676. So the overall metric for the state was still very close to 100%.

In the summer of 2012, we had some high ozone levels in a few counties. The levels for four counties exceeded the NAAQS. Those counties are Clark, Floyd, Greene and LaPorte. We added the populations of those counties and the overall metric dropped to 94.9%. The ozone levels only occurred on a few days and generally were not repeated this past summer.

In July of this year, U.S. EPA designated parts of five counties nonattainment for sulfur dioxide (SO2). These designations were based on measured air quality in those counties. The areas included are: Daviess County–Veale Township; Marion County–Center, Perry and Wayne Townships; Morgan County–Clay and Washington Townships; Pike County–Washington Township; and Vigo County–Fayette and Harrison Townships. SO2 levels in each of these areas are decreasing. However, U.S. EPA established a new one hour standard for SO2, and levels in these areas were above levels allowed under the new standard. The overall metric now stands at 87.6%.

The OAQ is working with the source which caused the lead problem. At this point we have recorded approximately a year and a half of air quality readings that meet the standard. However, it takes three full years of clean data before we can request that U.S. EPA redesignate this area as attainment. We are also working with the utilities that contributed to the SO2 problems. Strategies are being worked on to determine what controls or other changes are necessary to bring these areas back into attainment. Once again we will need to have three clean years of measured data before we can request that U.S. EPA designate these areas as attainment. So even as levels improve in these areas, they will still be shown as areas where the air quality is not meeting the standard.

The counties with ozone exceedances will be watched to see how future ozone levels trend. Ozone levels are very sensitive to weather conditions. If it is a very hot summer, we are more likely to have ozone exceedances. If we have cool summers, it is unlikely that we will have ozone exceedances. The form of the standard averages three years of data together to account for this variation in weather conditions. U.S. EPA is planning to lower the ozone NAAQS in the next year or two. When that happens we will likely have many areas of the state that will not meet the new ozone NAAQS. At that point the metric may drop again.

U.S. EPA has also changed the standard for small particles (PM-2.5) to allow less of the pollutant in the air. When we need to address this standard, we may have more areas of the state that will not meet the standard. Right now things are looking good that we may have the entire state meet the new standard for PM-2.5, but you never know.

In all of these cases, the air quality within the state is getting better. What is happening is that U.S. EPA is changing the national ambient air quality standards, to allow lower levels of pollutants in the air we breathe. When you compare existing levels against a stricter and stricter set of standards, we will have times where we do not meet the new standard. In those cases, we will work with the sources causing the problems to put new rules in place so that we can return the areas to attainment. However, this process takes many years. The key point to keep in mind is that the air quality levels actually measured continue to improve. It is the levels allowed by the standards that are decreasing faster than the air quality levels.

Keith Baugues