Reported air toxics emissions data


Air toxics emissions data for air pollution sources in Colorado are available through several different information sources.

Colorado Air Pollutant Emissions Notices (APENs)

Colorado Department of Public Health and Environment requires periodic reporting of air toxics emissions from stationary sources of air pollution through the Air Pollutant Emissions Notice (APEN) program. The APEN program covers more than 350 different pollutants. About 6,500 facilities report one or more air toxics on their APEN. 

APEN submittals are required from both existing and new or modified sources of air pollution. An APEN must be submitted for each source of emissions when uncontrolled air toxic emissions are estimated to be above 250 pounds per year for that source. 

APEN submittals must be renewed every five years, unless emissions change significantly to warrant a renewal before this timeframe. While APEN submittals are unique to each emission source, these estimates can be added together to estimate facility-wide emissions from multiple air toxic(s) sources.

APENs data and stationary sources of air pollution across Colorado

Air toxics emissions data for specific facilities are available for review on the Air Pollution Control Division's interactive map of stationary air pollution sources. For more information about how to use and access this tool, visit the division’s records management webpage. The same information is also available by searching the division’s records database.

Overview of Air Toxics Emissions Sources in Colorado

Oil and gas extraction is the leading sector for air toxics emissions from stationary sources of pollution across Colorado. This is followed by the utilities sector, which includes electricity generation and transmission, gas transmission pipelines, water and wastewater plants, and waste management. Manufacturing is the third largest, with non-metallic minerals such as cement and glass, as well as the production of ethanol, pharmaceuticals, food, and metal products contributing the largest air toxics emissions within this sector. The commercial and institutional sector includes a wide variety of facility types, and most of these emissions are from gas stations, fuel wholesalers, and automotive repair shops.


The data comes from the Colorado Department of Public Health and Environment Stationary Source APEN database, reflecting final calendar year 2022 emissions. Sectors were assigned based on NAICS code. More than 6,700 facilities reported one or more air toxic pollutants.

U.S. EPA Toxic Release Inventory (TRI) 

The EPA requires annual facility-wide reporting of toxic releases from selected larger facilities meeting the Toxic Release Inventory (TRI) reporting criteria. The TRI includes over 700 compounds. Toxic releases are categorized according to the type of release at the reporting facility, with air releases being one of the reported categories. The number of facilities reporting air releases to TRI is smaller than those reporting air toxics data to CDPHE’s Air Pollution Notice (APEN) program

Data reported to EPA is available on the EPA’s TRI website.

U.S. EPA National Emission Inventory (NEI)

Every three years, the EPA publishes a National Emission Inventory (NEI). The NEI includes a subset of air toxics emissions classified as federal hazardous air pollutants. The source of these emissions include:

  • Data reported to Colorado Department of Public Health and Environment through the Air Pollution Notice (APEN) program
  • Air toxics emissions reported the EPA’s Toxic Release Inventory (TRI). 

To fill data gaps, the EPA estimates emissions of certain air toxics that were not reported by the department for different types of emission sources by separating the reported volatile organic compounds, particulate matter, and chromium compounds into individual air toxics. These estimates are based on profiles specific to different processes such as different types of fuel combustion or manufacturing processes. 

Air toxics emissions for other sources that do not report to the state’s APEN program are also included in the NEI, such as:

  • Smaller stationary sources of air pollution that do not meet APEN reporting thresholds
  • Mobile sources of air pollution
  • Agricultural sources of air pollution
  • Residential sources of air pollution
  • Wildfires and other natural sources of air pollution.

These estimates are based on activity data for each sector.

Explore the latest NEI data on the EPA’s NEI website.

Colorado Annual Air Toxic Reports

Colorado law (HB22-1244) requires that each source of air pollution required to obtain an operating permit and synthetic minor sources of air pollution report annually on air toxics. These reports must be publicly available. The first reports are due on or before June 30, 2024.


The Air Pollution Control Division is providing additional resources for facilities required to report under this program.