Air Quality Monitoring

The cornerstone of an air quality agency is accurate monitoring of air pollution. The APCD is responsible for monitoring ambient air pollution in Louisville/Jefferson County, Kentucky.

Criteria Pollutants

The APCD currently measures the concentration of pollutants for which the U.S. EPA has created National Ambient Air Quality Standards (NAAQS), including:

  • ozone (O3)
  • carbon monoxide (CO)
  • sulfur dioxide (SO2)
  • nitrogen dioxide (NO2)
  • inhalable particulates (PM10)
  • fine particulates (PM2.5)
  • lead (Pb)*

The methods for collecting ambient air samples are as varied as the locations that are used by the APCD. For example, fine particles are collected by teflon filters inside the monitor. Those filters are then weighed to determine pollution levels to an extremely small amount. Other types of pollutants are measured by complicated electronic machines that take in air samples and determine pollution concentrations in real time. A dedicated staff of air quality professionals at the APCD maintains this equipment daily to guarantee accurate measurements. The data are sent electronically to the APCD to be shared with members of the community interested in air quality and its impacts.

Under the Clean Air Act, the EPA is required to review the NAAQS every five years. Many times, those reviews lead to changes in the standards which often prompt changes in monitoring requirements. These could be as simple as changing the levels monitored and as complicated as adding new sites and monitors.

* In 2016, the EPA authorized the APCD to discontinue active monitoring of airborne lead (Pb) because levels are far below the NAAQS and are not expected to increase at the present time.

Monthly Air Monitoring Report

Click here to see the monthly air monitoring report issued by the APCD Air Monitoring Section.

Siting of Monitors

Accurate representations of Louisville’s air require monitors to be located at varied sites throughout the community. For detailed information on APCD monitors and sites visit our Monitoring Sites page.

Our Cannons Lane Air Monitoring Station, 2730 Cannons Lane, has been classified as an NCore site by the EPA. NCore is a multi-pollutant monitoring network that integrates several advanced measurement systems for particles, pollutant gases and meteorology. The EPA coordinates with its state, local, and tribal partners who operate the NCore sites. There are several dozen NCore sites throughout the United States, located mostly in urban settings. The Cannons Lane Air Monitoring Station receives a portion of its power from solar panels purchased with a mixture of EPA grant dollars and funding from Louisville’s Air Quality Trust Fund.

The Kentucky Annual Ambient Air Monitoring Network Plan provides an annual overview of the air monitoring network in Kentucky, including our own monitoring section. This includes location of monitoring sites, sampling and analysis methods, operating schedule, and more.

Data Collection

Our monitoring program collects several different categories of data. After the data are collected, analyzed, and quality assured, they are often used to determine compliance with air pollution regulations and standards. The data may also be used in policy decisions at the federal, state, and local levels.

Air Toxics

The APCD is adding equipment to monitor for air toxics at two of its sites: 2730 Cannons Lane and 4201 Algonquin Parkway.

In addition, the APCD is assisting the U.S. EPA with a project to test new air toxics monitoring technology in Louisville’s Rubbertown industrial area.

Meteorological Data

Meteorological data such as wind speed and direction, temperature, rainfall, barometric pressure, and humidity are collected by the APCD to assist in making air quality forecasts and further analysis of air pollution data and episodes.


The APCD monitors radioactivity in Louisville. EPA’s RadNet is a national network of monitoring stations that regularly collect air, precipitation, drinking water, and milk samples for analysis of radioactivity. The National Air and Radiation Environmental Laboratory (NAREL) oversees RadNet monitoring. The APCD supports RadNet by collecting and processing air samples and providing NAREL real time data 24 hours a day, seven days a week. The radiation monitors use an alpha and beta counting system plus filters to measure isotopes of plutonium and uranium (Pu-238, Pu-239, Pu-240, U-234, U-235, U-238).

Data Analysis and Quality Assurance

All of the monitoring data collected by the APCD must be analyzed and validated. To ensure the monitoring data are valid, The APCD incorporates quality assurance measures into the monitoring process. The quality assured data is reported to EPA, NAREL, and others and may be used in a number of ways including:

  • Determining whether Louisville is meeting national standards for air pollution;
  • Forecasting air quality for the Louisville area; and
  • Informing federal, state, and local policy making.

Air Quality Forecasting

APCD staff use computer models along with meteorological data to project pollution levels and communicate them with the public. These forecasts are especially important during the summer months when pollution levels are typically higher. People with asthma or other lung and heart conditions rely upon accurate forecasting through the Air Quality Index to ensure that pollution levels have less of an impact on their health during these periods. The Air Quality Forecasts page has more information on forecasting in Louisville, including today’s forecast.

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