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

Siting of Monitors

View of the instrumentation at APCD's Cannons Lane Air Monitoring StationAccurate 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.

APCD’s Cannons Lane Air Monitoring Station has been classified as an NCore site by the U.S. Environmental Protection Agency (EPA). NCore is a multi-pollutant monitoring network that integrates several advanced measurement systems for particles, pollutant gases and meteorology. 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.

Data Collection

APCD’s 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.

Montage of three photos of APCD's air monitoring instruments, including one showing monitoring staff working on a particulate samplerCriteria Pollutants

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

The methods for collecting ambient air samples are as varied as the locations that are used by APCD. For example, fine particles are collected by small 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 APCD maintains this equipment daily to guarantee accurate measurements. The data are sent electronically to APCD to be shared with members of the community interested in air quality and its impacts.

Under the Clean Air Act, 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.

A montage of three photos of APCD's meteorological instruments

Meteorological Data

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


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. 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).A montage of three images of APCD's open path air monitoring instruments

Air Toxics

Levels of toxic chemicals in the air are monitored by the University of Louisville. However, APCD received a grant from EPA to conduct open-path monitoring of toxics along industrial fence lines. The study focuses on short-term averages over long time periods in locations that are considered to be at a higher risk because of their proximity to air toxic sources and/or the presence of sensitive populations.

APCD purchased two instruments with the grant funds, a fourier transform infrared spectrometer (FTIR) and an ultraviolet-differential optical absorption spectrometer (UV-DOAS). The initial phase of the project included comparison monitoring near toxics monitors operated by the University of Louisville. The equipment is being used to monitor areas identified in the project plan. APCD plans to continue monitoring with this equipment after the grant-funded study ends.

Data Analysis and Quality Assurance

All of the monitoring data collected by APCD must be analyzed and validated. To ensure the monitoring data are valid, 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:

  • Montage of Air Quality Index logo and CLAIRE computerDetermining 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 Forecast page has more information on forecasting in Louisville, including today’s forecast.