The Colorado Air Quality Control Commission (AQCC) adopted toxic air contaminant (TAC) reporting requirements into
Regulation 3 during an April 2025 rulemaking hearing. The April 2025 rulemaking hearing is the most recent step in a series of actions established under House Bill 22-1244 that aim to protect public health and the environment from the adverse effects of air pollution.
Background
House Bill 22-1244 was signed into law in June 2022, establishing requirements to develop an air toxics program and annual TAC reporting requirements. The first annual facility-wide TAC emissions report was due on June 30, 2024, for Title V and synthetic minor facilities. The TAC reporting data is expected to inform additional future monitoring and emissions control requirements, as well as a potential future air toxics permitting program.
Regulation 3 TAC Reporting
The AQCC held a rulemaking hearing on April 16-18, 2025 to establish regulatory requirements for TAC reporting under Regulation 3. The revisions to Regulation 3 were published to the Colorado Register on May 25, 2025, and are effective on June 14, 2025. It is anticipated that these requirements will be moved to Regulation 30 at a later date.
The TAC reporting requirements outlined in the rule include several significant changes to the TAC reporting program as it is currently established. The new requirements adopted into the rule will go into effect starting with the 2026 emissions report that will be due June 30, 2027. The reporting requirements established under the
current guidance will remain in effect for the 2024 and 2025 TAC emissions reports (due June 2025 and 2026, respectively).
Some of the key changes to reporting requirements include:
- TAC Pollutant List Changes. The TAC list will decrease from 477 pollutants to only 344 pollutants listed in Regulation 3, Appendix C. Two new pollutants will be added to the TAC list (black carbon and ultra-fine particles) that are currently not reportable under the rule.
- Exempted Sources. The rule introduces exemptions to TAC reporting, including exemptions for a variety of operations and emissions sources. Many of these exemptions line up with exemptions for emissions reporting and permitting under Regulation 3. The rule also clarifies that only stationary sources will be required to report emissions.
- De Minimis Exemption. The Regulation 3 changes also introduce de minimis reporting thresholds for TAC emissions listed in Appendix C. The thresholds will be based on post-control facility-wide emissions. Exempted sources should not be included when comparing emissions to the thresholds.
- Data Hierarchy. The rule requires that reporters use the best available methods to estimate emissions data. While not specifically outlined in the regulation, the Air Pollution Control Division (APCD) will release guidance with clarifications on the preferred emission estimation methods. Reporters are not expected to complete new testing or monitoring for TAC reporting purposes.
New Sources Subject to TAC Reporting
Currently, only synthetic minor and Title V major facilities are required to submit an annual TAC report. Under Regulation 3, the TAC reporting requirements will be expanded to include more sources. Sources that will be required to submit an annual TAC emissions report starting in reporting year (RY) 2026 include:
- Minor Sources Reporting under Regulation Number 7, Part B, Section V.
- Minor Sources Reporting to the EPA Toxic Release Inventory (TRI). Sources reporting under TRI with any stack or fugitive air releases of TAC above de minimis reporting thresholds.
- Minor Sources with No Annual Reporting since 2020. Minor sources that have not reported annual emissions since January 1, 2020, through any of the following programs: Regulation 3 APEN requirements, Regulation 22 GHG reporting, or EPA TRI reporting.
- Certain Additional Industrial Process Sources. Minor sources using or emitting ethylene oxide and those with industrial process emissions (except combustion emissions) of hexavalent chromium, nickel, or cadmium above de minimis reporting thresholds.
Regulation 3 Fee Increases
During the April 2025 rulemaking hearing, the AQCC also approved the Division’s proposed fee increases. These fee changes were introduced to cover indirect and direct costs required to develop and administer the programs and services to protect air quality in Colorado. Except as noted, the fee updates will become effective July 1, 2025. The new fees established in Regulation 3 are presented below.
TABLE 1
| Annual Fee | Previous Rate | Unit | % Increase | New Fee |
| Criteria Pollutant Emissions |
| 2025 Emissions | $36 | Per ton | 133.3% | $84.00 |
| 2026 Emissions and Onward | $36.00 | Per ton | 66.7% | $60.00 |
| HAP Emissions |
| 2025 Emissions | $239.00 | Per ton | 133.1% | $557.00 |
| 2026 Emissions and Onward | $239.00 | Per ton | 66.5% | $398.00 |
| APEN Filing Fee | $242.00 | Per APEN | 50.0% | $363.00 |
| Permit Processing | $119.00 | Per hour | 51.3% | $180.00 |
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Upcoming and Future Toxics Rulemaking
In addition to the recently finalized TAC rules and proposed rules, the Division will be undertaking the additional future rulemakings per HB22-1244:
- July 2025 – Four additional toxic monitoring sites begin operation.
- December 2025 – conduct a needs assessment for an air toxics permitting program for stationary sources.
- April 2026 – develop and adopt health-based standards for PTACs and emission control regulations for new and existing stationary sources to reduce emissions of PTACs.
- Hearings are scheduled for September 2025 and December 2025 ahead of the final rulemaking decision
- Beginning September 2029 and at least every five years thereafter: determine whether to identify additional PTACs, whether to set acute exposure limits for PTACs, determine whether to revise the health-based standards.
- No later than September 30, 2030 and at least every five years thereafter: determine whether to add additional air pollutants to the TAC list
- Beginning September 2030 and at least every five years thereafter: adopt emission control regulations for any new PTACs and determine whether to revise existing emission control regulations.
