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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

On June 2, 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 standards for each priority toxic air contaminant.
  3. 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 will request a rulemaking to establish health-based standards for the priority air toxics listed above. The hearing would consider revisions to Air Quality Control Commission Regulation 30.

The health-based standards will serve as benchmark concentrations. 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 is considering 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 health-based standards. Their contributions ensured that the benchmarks reflect the latest research and best practices. The division will bring the proposed standards before the commission for a rulemaking hearing in May 2025.

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 December 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.
  • 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 standards 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 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

The air division hosts public meetings on air toxics and associated regulatory requirements. Registration is required.

Air toxics public meetings on health-based standards and the permitting report

The division anticipates holding meetings in the future to evaluate:

  • 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.

Contact us

Questions? Email the division’s air toxics team at cdphe_apcd_airtoxics@state.co.us.

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