On Nov. 25, 2014, EPA proposed revising the National Ambient Air Quality Standard (NAAQS) for ozone, recommending a standard between 65 to 70 parts per billion (ppb) for both the 8-hour primary and secondary standards. The current ozone standard is set at 75 ppb. Earlier this year, the Clean Air Scientific Advisory Committee (CASAC) concluded that scientific evidence supported a standard between 60 to 70 ppb.

Ultimately, EPA decided to propose a new standard between 65 and 70 ppb, but is taking comment on whether a 60 ppb standard should be established for the primary standard or whether the existing 75 ppb standard should be retained.

Currently, the northern Kentucky counties of Boone, Kenton and Campbell are designated as partial nonattainment with the existing 75 ppb ozone standard. But other counties could ultimately be designated as nonattainment depending on which value EPA chooses for the final standard.

In anticipation of the EPA’s proposal to revise the ozone NAAQS, Kentucky Governor Steve Beshear sent a letter to President Barack Obama on Nov. 21 outlining the Governor’s concerns relating to the economic impact of the proposed standards and recommending that the standard remain unchanged. The letter indicates that if a 60 ppb standard is ultimately chosen all 29 of Kentucky’s air monitors would exceed the standard.

Indiana may fare a little better under the proposed ozone standard. Speaking at the AWMA Technical Workshop in Indianapolis on Dec. 12, 2014, IDEM Assistant Commissioner for the Office of Air Quality Keith Baugues Reported that only one Indiana county (Laporte) is currently exceeding the 2008 8-hour ozone standard of 75 ppb. Assistant Commissioner Baugues reported that projected ozone decreases from other programs will result in only one county not meeting a 70 ppb standard with some uncertainty for five other counties. A 65 ppb ozone standard is projected to result in six counties in nonattainment with some uncertainty for another five counties.