Colorado’s Air Pollution Control Division proposed shifting oversight of solid particulates as small as one-seventh the width of a human hair from federal to state-only authority on Dec. 19, citing more than 20 years of compliance with national standards.

The proposal seeks to repeal EPA-approved particulate controls in seven areas once out of compliance with Clean Air Act standards: Aspen, Cañon City, Denver metro, Lamar, Pagosa Springs, Steamboat Springs and Telluride.

The proposed rule would remove federal oversight on particulate emissions, including stoves, sanding and vehicle emissions, making them state-only. It shifts control to a state authority, allowing revisions without federal approval under the Clean Air Act, which permits states to adopt stricter standards.

States retain the right to enforce standards or limitations on emissions of air pollutants stricter than federal standards, according to the act.

The Air Quality Control Commission adopted these plans in the 2000s as part of federally-approved State Implementation Plans.

The division called the changes an administrative action with no impact on particulate levels or requirements of individuals or entities.

State law gives the commission authority to make rules to meet Clean Air Act standards, the proposal said.

The proposal aligns with Gov. Jared Polis’ policies advancing stricter vehicle emission standards to reduce criteria pollutants, including PM10 from on-road sources.

Polis signed a compact with California and 13 other states, plus the District of Columbia, in July 2020 to align medium- and heavy-duty vehicle emissions with California’s stricter-than-federal rules.

The Multi-State Medium- and Heavy-Duty Zero Emission Vehicle Memorandum of Understanding commits signatories to strive for 30% zero-emission vehicle sales in that category by 2030, and 100% by 2050.

“The Signatory States agree to strive to make sales of all new medium- and heavy-duty vehicles in our jurisdictions zero-emission vehicles by no later than 2050,” the memorandum said. “In order to ensure adequate progress toward the 2050 goal, the Signatory States will strive to make at least 30 percent of all new medium- and heavy-duty vehicle sales in our jurisdictions zero-emission vehicles by no later than 2030.”

Polis’ 2019 executive order directed the adoption of California’s zero-emission vehicle program, which Colorado implemented to require more electric vehicle sales.

Polis stated a goal of 940,000 electric vehicles on Colorado roads by 2030 in the state’s 2020 Electric Vehicle Plan.

“We applaud the EPA on this new rule that will significantly reduce emissions from trucks and buses nationwide, improving our air quality and public health,” Polis said in a statement on the federal heavy-duty vehicle standards in 2024. “Colorado is proud of our nation-leading work to reduce air pollution and greenhouse gas emissions, which includes a successful transition to zero-emission trucks and buses.”

Environmental groups supporting Polis’ policies describe strict criteria pollutant standards as tools to phase out internal combustion engine vehicles.

“The adoption of the Advanced Clean Cars II (ACCII) regulation means that by 2035, every new car and truck sold in California would be zero-emission,” the Natural Resources Defense Council said in a blog post on California’s standards, which Colorado adopted in modified form.

Industry leaders oppose such standards, arguing they effectively ban internal combustion engines through stringent limits on pollutants like PM10.

“Auto Innovators does not believe (the proposed standards) can be met without substantially increasing the cost of vehicles, reducing consumer choice, and disadvantaging major portions of the United States population and territory,” John Bozzella, CEO of the Alliance for Automotive Innovation, said.

Government documents connect vehicle traffic to particulate pollution from dust kicked up by cars on roads and vehicle emissions.

Federal actions revoked California’s waivers on June 12, 2025, affecting Colorado’s adoption of those standards.

“We officially rescue the U.S. auto industry from destruction by terminating California’s electric vehicle mandate,” President Donald Trump said.

The division scheduled a rulemaking request for Feb. 19.

A public meeting is set from 10 a.m. to noon on Jan. 10.

Contact Rick Coffin at rick.coffin@state.co.us for details.