A breath of fresh air: Building an air toxics framework in Colorado, step by step

Colorado’s latest move to adopt emissions control regulations is a significant step forward for public health, especially as national protections regress.

By Meagan L. Weisner and Ben Showalter, MD, EDF Fellow

What’s new: Colorado just joined a growing number of states seeking to fill a federal gap in community protections from cancer-causing air pollutants. Last month, the Colorado Air Quality Control Commission (AQCC) adopted limits for a set of five priority toxic air contaminants (PTACs) from certain polluting facilities. The five contaminants that the Commission put on its priority list were those that it determined pose the greatest threat to Coloradans’ health. They include:

• Formaldehyde,
• Benzene,
• Chromium compounds (hexavalent),
• Ethylene oxide and
• Hydrogen sulfide

The backstory: The new regulations were set in motion by House Bill 22-1244, which directed the Commission to identify the five priority pollutants, adopt health-protective benchmarks to track them and then set up regulations to limit them.

The Commission adopted benchmarks for the five contaminants and completed a needs assessment in 2025 to serve as a framework for potential air toxics permitting in Colorado, a move that’s still awaiting legislative approval.

Stronger protections, especially for hardest-hit communities: The new benchmarks represent a pivotal milestone in Colorado’s efforts to protect residents’ health. The Commission adopted a protective cancer risk level of one-in-one million for benzene, along with a more protective standard for the chronic, non-cancer benzene benchmark than what was originally proposed.

While environmental groups and communities near oil and gas operations praised the benzene health-based benchmark, they also raised concerns that other benchmarks were weakened, may be difficult to enforce, and may not protect those in disproportionately impacted communities. Last month’s rulemaking addressed some of these concerns by setting emissions control requirements that address some inequities. For example, after extensive discussion the Commission determined that facilities that emit more than 4,000 pounds of formaldehyde per year and that are located within one mile of a disproportionately impacted community can be subject to additional emissions control requirements.

Environmental organizations and local governments strongly supported the one-mile threshold while industry groups advocated for distances as low as 1,000 feet. The final decision reflects the state’s recognition that proximity to pollution sources matters — and that stronger safeguards are needed to protect those most at risk from exposure to pollution via multiple sources.

What’s next? To fully protect public health, Colorado needs to move beyond analyzing air toxics like benzene to implementing enforceable emission reductions for oil and gas sources, particularly in upstream and midstream oil and gas operations where exposures can be significant.

The latest cumulative impacts report released in May 2026 by the Colorado Energy & Carbon Management Commission (ECMC) noted that while benzene concentrations in the Front Range fell over the past four years, they were still higher there than in any other region for wells approved in 2025. As operators drill farther distances, per-well emissions are rising. Incorporating robust benzene standards and consistent reductions requirements will be key to closing this gap.

The good news is that Colorado’s framework is designed to evolve. The Commission reviews air toxics regulations every five years, enabling regular opportunities to strengthen protections as new data and technologies become available. This mandatory review cycle ensures that the state can continue to adapt and improve its approach over time. EDF remains committed to working with all stakeholders — such as community advocates, local government and industry — to ensure Colorado’s rules deliver strong, enforceable public health protections.

For Coloradans and environmental advocates, the message is clear: meaningful progress to cut pollution is happening. But continued engagement will be essential to ensure that future rulemakings close remaining gaps — especially in the oil and gas sector — to fully realize the promise of clean, healthy air for everyone in the state.

Meagan Weisner is a Senior Scientist with EDF’s Healthy Communities team. Ben Showalter is an family physician and EDF Fellow focused on the intersection of climate pollution and human health.