Air Quality


Why is air quality important and how do transportation (mobile) sources affect it? Having clean air is important to both our health and the environment. The cars, trucks, planes, trains, and boats that move people and freight emit pollutants such as carbon dioxide, nitrogen oxides, and fine particles (particulates). To keep these pollutants at a level that protects our health, the Environmental Protection Agency (EPA) has created National Ambient Air Quality Standards (NAAQS). Each county in Kentucky has been designated to have met the NAAQS (attainment) or not (nonattainment). To ensure those levels are not exceeded in the future, we must estimate future pollutant levels using computer models in a process called Transportation Conformity. 

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.


In July 2012, EPA designated the nonattainment areas for the 2008 8-hour ozone standard (0.075 ppm).  Only the partial (northern halves) of Boone, Kenton and Campbell Counties are nonattainment. All other areas within the Commonwealth were either unclassifiable/attainment for the 2008 8-hour ozone standard. See ozone map above. For more information, see EPA's 8-hour Designation.
In October 2015, EPA established that they were tightening the ozone standard to 0.070 ppm. The EPA will not be issuing their final area designations until October 2017. For further information on the 2015 8-hour standard, see EPA’s 2015 8-hour regulatory actions.

Fine Particulate Matter:

In December 2012, the EPA announced that they were tightening the PM2.5 standard to 12µg/m3. In December 2014, EPA issued their final designations, which include Jefferson and Bullitt (partial) Counties being nonattainment. The rest of the Commonwealth was either unclassifiable/attainment.
In March 2015, the EPA revised their final designations and reclassified Jefferson and Bullitt (p) Counties to unclassifiable/attainment. This meant all areas within the Commonwealth were either unclassifiable/attainment for the 2012 PM2.5 standard.
The EPA partially vacated the 1997 PM2.5 standard, but not for transportation conformity purposes. This means the counties from the 1997 PM2.5 standard must still do conformity until the standard is fully vacated. These counties include: Boone, Boyd, Campbell, Jefferson, Kenton, and Lawrence (partial). EPA announced in April 2016 that the 1997 PM2.5 standard should be fully vacated by the end of the summer. See PM2.5 map above. 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 rulemaking on national performance measures took effect. One of the measures that has been delayed indefinitely is the one pertaining to GHGs. However, just because it has been delayed does not mean Kentucky is waiting for the measure to be implemented before taking action. In Louisville, city, county, and state officials are working together to establish a Community Greenhouse Gas (GHG) Inventory. This will allow Louisville to establish a GHG inventory and forecast future GHG emissions for city. It will also help to create GHG emission reduction targets and a plan 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.

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 traffic 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 2010b 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 traffic model 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