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Air Quality in Indiana

Air Quality in Indiana > Air Quality 101 Air Quality 101

December 9, 2015: Ozone Levels in Indiana, A Success Story

Hoosiers have seen ozone levels improve significantly over the past 15 years. Over this time period, the United States Environmental Protection Agency has tightened the standard twice—first, from 85 to 75 parts per billion (ppb), and very recently, to 70 ppb. Indiana keeps rising to meet the challenge.

Compliance with the ozone standard is determined by looking at the most recent three years of data. The new standard of 70 ppb will take effect for the 2014 to 2016 season. Whether an area meets or does not meet the standard will not be determined until the data for next year’s ozone season (2016) is available. But like all states, we are reviewing data from the 2013 to 2015 season, to see where we are in comparison with the new standard. Based upon the 2013 to 2015 data, all counties within Indiana meet the new ozone standard of 70 ppb. In each case, the ozone levels are showing a downward trend.

In most cases, this downward trend is significant, at a 99.9 percent confidence level. Normally a trend is considered significant if it has a confidence level of 95 percent or greater. This implies that over many years, ozone levels are going down. It does not guarantee that levels next year will be lower than they were in the previous year. Ozone levels are driven by weather conditions, especially temperature. If we have a year with maximum temperatures or many days at or above 90 degrees, we can expect to have elevated ozone levels. During this period when ozone levels have decreased in Indiana, there have been counties that have had design values above the standard. However, levels of ozone in the air we breathe are the lowest they have ever been. Officially we will not know whether we are able to meet the new 70 ppb standard until next summer’s ozone levels are monitored. There is reason to expect that they will continue to decrease.

Listed below are the ozone design values by county for each three year period from 2000 to 2002 through 2013 to 2015. A design value is estimated by determining the maximum 8-hour ozone level for each day in a year and then determining the fourth highest 8-hour value. The fourth highest values for the three years are averaged to arrive at the design value for the three year period. This value is then compared to the standard to determine whether the area does or does not meet the standard.

Ozone Design Values in Indiana (parts per billion)
County Time Period Trend Confidence Level
2000- 2002 2001- 2003 2002- 2004 2003- 2005 2004- 2006 2005- 2007 2006- 2008 2007- 2009 2008- 2010 2009- 2011 2010- 2012 2011- 2013 2012- 2014 2013- 2015
Allen 88 88 85 83 77 78 73 71 67 68 71 69 67 62 Down 99.9
Boone 88 90 86 80 78 81 78 75 71 70 74 73 71 66 Down 99.9
Carroll 87 84 82 75 73 75 72 68 66 67 71 69 68 64 Down 99.9
Clark 90 92 88 81 77 83 81 77 73 75 81 78 72 69 Down 99.9
Delaware 89 88 83 78 74 77 71 69 65 68 70 68 63 57 Down 99.9
Elkhart 99 93 87 83 76 78 72 70 64 66 70 67 61 56 Down 99.9
Floyd 83 86 84 79 75 79 77 73 70 71 79 78 73 66 Down 99
Greene 89 88 84 80 76 79 77 74 71 74 78 76 71 66 Down 99.9
Hamilton 93 96 92 87 79 82 78 76 72 71 73 70 65 61 Down 99.9
Hancock 92 94 88 81 75 78 76 74 71 69 67 64 59 58 Down 99.9
Hendricks 88 85 81 76 74 76 73 72 68 68 68 65 61 56 Down 99.9
Huntington 86 84 80 76 73 76 70 66 61 64 66 65 60 56 Down 99.9
Jackson 85 85 80 75 73 76 74 70 67 66 67 65 64 63 Down 99.9
Johnson 87 86 83 76 76 78 75 73 70 69 70 68 64 60 Down 99.9
Lake 92 90 83 78 77 85 77 70 67 68 73 71 69 65 Down 99.9
LaPorte 92 93 86 80 76 78 70 68 65 72 83 83 79 68 Down 95
Madison 91 95 89 80 74 76 72 69 64 66 70 69 63 57 Down 99.9
Marion 90 92 88 81 76 79 78 77 73 74 74 74 71 65 Down 99.9
Morgan 88 85 82 77 75 79 76 74 67 68 69 70 67 64 Down 99.9
Perry NA NA 78 82 81 81 77 72 70 70 75 73 70 66 Down 99
Porter 90 87 84 78 76 81 74 73 67 67 72 72 73 68 Down 99.9
Posey 87 84 81 75 68 71 69 72 68 70 71 70 66 65 Down 99
St Joseph 90 93 88 82 77 79 73 71 63 64 71 73 71 66 Down 99.9
Shelby 93 94 87 80 74 78 75 75 70 72 75 75 70 62 Down 99.9
Vanderburgh 83 83 82 77 75 80 80 76 70 70 73 74 71 68 Down 99.9
Vigo 91 87 83 76 73 73 70 66 63 64 68 67 66 62 Down 99.9
Warrick 84 85 83 77 77 80 77 72 68 70 74 73 71 65 Down 99.9

Comments on this article and/or any previous article can be sent to kbaugues@idem.in.gov.

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