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May 2025 update: The Air Pollution Control Division has completed the initial public input process on establishing health-based standards for the state’s five priority air toxics. Next, the Air Quality Control Commission will consider adopting the proposed rule. You can find the rulemaking hearing date and schedule on the commission’s calendar.
There are several ways to stay engaged in the rulemaking process:
- Submit written comments or questions about the proposed rule to the commission directly: [email protected]. These written comments will be included in the hearing record if submitted after the notice is published.
- Participate in the rulemaking hearing, which is open to the public. The commission typically posts a meeting registration link, with optional public comment registration on its website about two weeks before a rulemaking hearing. Hearing documents are available on the commission’s website 3-4 months prior to the hearing.
- Become a party to the rulemaking hearing. More information is available on the commission’s web page on what party status means and how the process works.
- Sign-up for email updates from the Air Pollution Control Division for information on future air quality rulemakings and public participation opportunities.
During its May 2025 meeting, the Colorado Air Quality Control Commission set a rulemaking hearing in September 2025 to establish health-based standards for the state’s five priority air toxics. Click here to read the proposed updates to Colorado Air Quality Regulation 30. The commission welcomes public feedback via email at [email protected].
Background
On June 2, 2022, House Bill 22-1244: Public Protections from Toxic Air Contaminants was signed into law. This law requires the state to:
- Identify priority toxic air contaminants.
- Adopt health-based standards for each priority toxic air contaminant.
- Develop a permitting needs assessment report.
These requirements would be accomplished through rulemaking actions by the Air Quality Control Commission. The CDPHE Air Pollution Control Division drafts rule proposals to bring before the commission.
Priority toxic air contaminants
On January 17, 2025, the commission adopted the new rule identifying five priority air toxics. The final rule language is available on the commission’s regulations web page.
The commission will review this list every five years to determine whether to add more priority air toxics.
Health-based standards
During the Colorado Air Quality Control Commission’s meeting on May 15-16, 2025, the CDPHE Air Pollution Control Division requested a rulemaking to establish health-based standards for the priority air toxics listed above. The commission set the rulemaking hearing for September 2025 to consider revisions to Air Quality Control Commission Regulation 30.
The proposed health-based standards will serve as guidelines. They will be based on the amount of each individual priority toxic air contaminant that can be in the air while still protecting public health. The division considered several factors when drafting the proposed standards, including:
- Best available peer-reviewed toxicity values.
- Standards adopted in other states.
- Effects of exposure on vulnerable populations.
- Both cancer-related and non-cancer-related health risks.
- A sufficient margin of safety to account for variations in population sensitivity to PTAC exposure.
- Input from the scientific community.
- Risk levels for cancer and non-cancer health impacts used to determine the standards.
The division consulted with the scientific community to gather expert input on developing the health-based standards. Their contributions ensured that the benchmarks reflect the latest research and best practices.
Permitting needs assessment
The division is developing a report to assess permitting needs for stationary sources that release priority toxic air contaminants.
Key components of the needs assessment report:
- Recommendations on the scope of the permitting program, including permit types, geographic areas, and affected industries.
- Procedures and timelines for notifying existing sources that may be covered under the program, conducting health risk assessments, and identifying strategies for reducing air toxics emissions through permitting.
- Program costs and potential funding mechanisms to support implementation.
The division will likely accept written comments on the draft report in the fall of 2025 before submitting it to the general assembly by Dec. 31, 2025. The report will be discussed during SMART Act hearings in early 2026, during which legislators will review findings and potential next steps.
Scientific community technical working group
The air division convened a scientific community technical working group from January 2024 to February 2025. The working group focused on the framework for identifying priority toxic air contaminants and factors that influence the health-based standards. This working group aligns with the requirements of House Bill 22-1244: Public Protections from Toxic Air Contaminants.
The working group and associated outreach provided opportunities for scientific experts to participate. The goal was to develop collaborative, science-based solutions that prioritize transparency and inclusivity.
The technical working members provided a diverse mix of expertise in the effects of air toxics exposure. It included individuals with expertise in ambient air concentrations and how those relate to assessing human health exposures.
The working group included representatives from:
- Academia.
- Environmentally-focused non-governmental organizations.
- Local governments.
- The regulated community.
Past working group meeting dates and resources.
- Jan. 31, 2024.
- Agenda: Clarified the scope, purpose, and intent of the working group, and an overview of data sources to help develop an air toxics prioritization framework.
- January 31 presentation slides.
- Working group scope of work.
- April 24, 2024.
- Agenda: Obtained feedback on data sources and prioritization framework for the priority toxic air contaminant.
- April 24 presentation slides.
- June 26, 2024.
- Agenda: Discussed the revised prioritization framework and resulting options for priority toxic air contaminants.
- June 26 presentation slides.
- Sept. 10, 2024.
- Agenda: Discussed technical factors informing the health-based standards that will be established for each priority toxic air contaminant.
- September 10 presentation slides.
- Nov. 21, 2024.
- Agenda: Discussed technical factors informing the health-based standards and planning for the February public hearing.
- November 21 presentation slides.
- Jan. 22, 2025.
- Agenda: Reviewed the draft presentation related to the health-based standards that CDPHE staff presented based on the group’s feedback.
- The final presentation was presented during the February 2025 commission meeting.
Public meeting opportunities
As of May 2025, the division does not have more upcoming meetings related to priority air toxics. The division anticipates holding meetings in the future to evaluate:
- Additional details on a potential air toxics permitting framework.
- Development of emission control strategies to reduce emissions of priority air toxics.
- Whether to incorporate acute exposure limits into health-based standards.
- Input on more priority air toxics beyond the five the commission adopted in January 2025.
The division will publish any future public participation opportunities related to the priority air toxics on this web page as they become available.
The air division hosted public meetings to share information on the selection of 5 priority air toxics and updates on the annual emissions reporting rule.
- Virtual meeting: Tuesday, April 8, 2025.
- Virtual meeting: Saturday, March 29, 2025.
- Virtual meeting: March 12, 2025.
- Virtual meeting: Wednesday, Dec. 4, 2024.
- Virtual meeting: Saturday, Sept. 24, 2024.
- Virtual meeting: Saturday, Aug. 24, 2024.
- Virtual meeting: Tuesday, July 23, 2024.
- Virtual meeting: Saturday, June 1, 2024.
- Virtual meeting: Thursday, Feb. 8, 2024.
Press releases
Jan. 17, 2025: Colorado takes action towards reducing pollution from air toxics.
July 22, 2024: State health department seeks input in identifying priority air toxics to address and establish health-based standards.
Contact us
Questions? Email the division’s air toxics team at [email protected].
Stay informed. Subscribe to receive email updates from the division.
Get involved. Check the air division’s public participation web page for upcoming opportunities to provide feedback or learn more.