Air Quality


Air Quality Nonattainment or Maintenance Areas

KY Air Quality Designations​

Areas where air pollution levels persistently exceed the standards may be designated as nonattainment. These areas may consist of a county, a partial county or a group of counties. Once the area emissions fall below the standard, the area may be redesignated as "attainment with an approved maintenance plan". For additional explanation of these terms, please see Air Quality Terms and Abbreviations. Further information can be found in the Air Quality FAQ Brochure.


On October 1, 2015, EPA announced they were tightening the ozone standard from 0.075ppm to 0.070ppm to provide increased protection of public health.  On September 30, 2016, Kentucky submitted to EPA their recommendations on which areas in the state should be either attainment or nonattainment.  EPA established they would be providing two rounds of designations.  The first round on November 6, 2017, stated EPA intended to designate 114 out of the 120 counties to be classified as attainment/unclassifiable relating to the 2015h ozone standard.  The second round on December 20, 2017 stated EPA intended to designate 6 out of the 120 counties to be classified as nonattainment relating to the 2015 ozone standard.  Those counties were Oldham, Jefferson, Bullitt, Boone (partial), Kenton (partial), and Campbell (partial).  EPA on June 4, 2018 published the Federal Register making their intentions permanent.  On August 3, 2018, the 2015 ozone standard took effect. 
For further information on the 2015 8-hour standard, see EPA's 8-hour ozone Designation.

Fine Particulate Matter:

On December 14, 2012, the EPA announced they were tightening the PM2.5 standard from 15 µg/m3 to 12 µg/m3 to improve public health. EPA established they would be providing the initial round of designations by the end of 2014. On December 18, 2014, EPA intended to designate 118 out of the 120 Kentucky counties to be classified as attainment/unclassifiable relating to the PM2.5 standard. They also intended to designate 2 out of the 120 Kentucky counties to be classified as nonattainment relating to the 2012 PM2.5 standard. Those counties were Jefferson and Bullitt (partial). In March 2015, EPA revised their final designations and reclassified the counties of Jefferson and Bullitt (partial) to attainment/unclassifiable. This meant all areas within the Commonwealth were now attainment/unclassifiable for the 2012 PM2.5 standard.


For more information, see EPA's Fine Particulate Matter (PM2.5) Designations.

Greenhouse Gas (GHG):


GHGs are gases located in the earth's atmosphere that can either absorb or emit radiation, and can cause the atmosphere to trap in heat. The most common gases that make up GHGs include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Please refer to our ozone section above for further information regarding ozone. The transportation sector makes up about 27% of the total U.S. GHG emissions. So here at transportation, we are looking for ways to help reduce that percentage. For more information, see EPA's Greenhouse Gas (GHG) Emissions.


In May 2017, almost all the FHWA final rulemakings on national performance measures took effect. One of the measures being delayed indefinitely was the one pertaining to GHGs. On May 30, 2018, FHWA formally repealed the performance measure pertaining to GHGs. However, just because it has been repealed does not mean Kentucky has not been taking action. In Louisville, city, county, and state officials have been working together since May 2016, to establish a Community Greenhouse Gas (GHG) Inventory, which was completed in 2018. This allowed Louisville to establish a GHG inventory and forecast future GHG emissions for the city. It has also helped to create GHG emission reduction targets and in 2019, the city will be creating a strategy to meet those reduction targets. In the months and years to come, more initiatives like this one will be on the horizon for other cities in Kentucky.


For more information, see Louisville’s Greenhouse Gas (GHG) Inventory


Transportation Conformity:

The State Implementation Plan (SIP) defines the future maximum levels (called budgets) for each pollutant in each nonattainment and maintenance area. Transportation Conformity is a process that uses transportation and air quality models to examine future levels of emissions for each of these areas and ensures that the transportation plan does not worsen or cause air quality problems. Typically, a travel demand model is developed based on planned roadway projects to determine projected traffic patterns, volumes, and speeds. These numbers, along with vehicle fleet characteristics and environmental information, are entered into the EPA MOVES 2014b emissions model to determine future emission levels. If the emission levels calculated are less than the budget for that pollutant, the area's long range transportation plan is determined to be "in conformity."

During the planning process, federal, state, and local transportation and environmental agencies consult and come to agreement on the inputs that are entered into the travel demand and MOVES 2010b model. Each time the Long-Range Transportation Plan (LRTP) or the short-range transportation plan, Transportation Improvement Program (TIP), is updated, transportation conformity must be examined. For information on transportation conformity at the federal level see,

Congestion Mitigation and Air Quality (CMAQ)

Federal transportation legislation established the Congestion Mitigation and Air Quality (CMAQ) program to provide funding for projects that improve traffic flow, reduce congestion, and ultimately improve air quality in designated nonattainment or maintenance areas. See Kentucky CMAQ Program for application and program requirements. For federal CMAQ information, see FHWA CMAQ Program.

Air Quality Information

Presentations, Reports, and Brochures

Past Air Quality Conference                                       

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