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Priority toxic air contaminants

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Ayuda en el idioma de su preferencia: ofrecemos asistencia en el idioma de su preferencia, sin cargo alguno. Si desea solicitar asistencia en español o en otro idioma, envíe un correo electrónico a cdphe_apcd_outreach@state.co.us. Indique el tema y la frase “language assistance” (asistencia en otro idioma) como asunto de su mensaje. De ser posible, incluya un enlace a la información que desea consultar, como la página web o el documento.

Background

In June 2022, House Bill 22-1244: Public Protections from Toxic Air Contaminants was signed into law. This law requires the state to:

  1. Identify priority toxic air contaminants.
  2. Adopt health-based benchmarks for each priority toxic air contaminant.
  3. Develop a permitting needs assessment report for toxic air contaminants.
  4. Adopt emission control regulations for each priority toxic air contaminant.

These requirements must 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 benchmarks

On Sept. 19, 2025, the commission approved health-based benchmarks for each of the five priority air toxics.

The benchmarks identify levels of pollutants below which adverse health effects are not expected to occur, assuming a continuous lifetime exposure, including for children, older Coloradans, and people with existing health conditions.

Next, the chronic benchmarks will be submitted to the Colorado General Assembly in December 2025.

The commission will review the chronic health-protective benchmarks every five years and determine whether adjustments should be made. Additionally, the Commission must determine whether to add any benchmarks for shorter-term, or acute exposures by September 2029.

Permitting needs assessment

The division held a public comment period and two public meetings in September 2025 on its draft report assessing potential permitting needs for air toxics. The division is reviewing and considering all feedback received while finalizing the report. The comments on the draft report are available in English and Spanish. The report will be submitted to the General Assembly by Dec 31, 2025 for consideration. If the General Assembly approves, the final report will serve as a framework for a potential air toxics permitting program in Colorado. The draft report is required by the Public Protections from Toxic Air Contaminants Act.

Key components of the needs assessment report:

  • Recommendations on the scope of the potential air toxics permitting program. This includes 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 to support implementation.

Meeting recordings and presentation materials can be found in the past public meetings and resources section of this web page.

Emission control regulations

The commission must adopt emission control regulations to address each priority toxic air contaminant no later than April 30, 2026. The regulations must aim to reduce existing emissions and place more stringent control requirements on new sources of the priority toxic air contaminants. 

The division will hold a second public meeting this fall to discuss developing emission control regulations and potential revisions to Air Quality Control Commission Regulation 30. The public meeting will provide details about the types of emission control strategies under consideration and the scope of potentially impacted industries. There will be an opportunity to ask questions and provide public comment.

The division posted a regulatory concepts document on Oct. 17, 2025. Information on how to participate in this rulemaking process is available on the division's outreach page for regulations.

View the resources for the Oct. 22 and Nov. 8 public meeting in the past public participation section.

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 benchmarks. 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.
  • April 24, 2024.
  • 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 benchmarks that will be established for each priority toxic air contaminant.
    • September 10 presentation slides.
  • Nov. 21, 2024.
  • Jan. 22, 2025.
    • Agenda: Reviewed the draft presentation related to the health-based benchmarks that CDPHE staff presented based on the group’s feedback.
    • The final presentation was presented during the February 2025 commission meeting.

Public meeting opportunities

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 updates on the selection of five priority air toxics, the annual emissions reporting rule, the health-based benchmarks, the permitting report, and air toxics emission control regulation strategies.

Press releases

Sept. 19, 2025: Commission approves health benchmarks for five toxic air pollutants.

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 cdphe_apcd_airtoxics@state.co.us.

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.