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Colorado is tackling air pollution in vulnerable neighborhoods by regulating five air toxics

The Globeville, Elyria-Swansea and Commerce City communities in metro Denver are choked by air pollution from nearby highways, an oil refinery and a .

While these neighborhoods have , they’re not the only ones in .

Now, Colorado is taking a major step to protect people from air pollutants that cause cancer or other major health problems, called “air toxics.” For the first time, the state is developing its own .

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CU Boulder researcher Jenni Shearston studies chemical exposure and health, measuring and evaluating the impact of air pollution on people’s well-being.

In January 2025 as “priority” chemicals: benzene, ethylene oxide, formaldehyde, hexavalent chromium compounds and hydrogen sulfide.

The state is in the process of setting health-based standards that will limit the amount of each chemical allowed in the air. Importantly, the standards will be designed to protect people exposed to the chemicals long term, such as those living near emission sources. Exposure to even , such as benzene, .

As a researcher studying , I measure and evaluate the impact of air pollution on people’s well-being.

Colorado’s new regulations will draw on expert knowledge and community input to protect people’s health.

Communities know what needs regulation

In your own community, is there a highway that runs near your house or a factory with a bad odor? Maybe a gas station right around the corner? You likely already know many of the places that release air pollution near you.

When state or local regulators work with community members to find out what air pollution sources communities are worried about, the partnership can lead to a system that better .

For example, partnerships between community advocates, scientists and regulators in heavily polluted and marginalized have had big benefits. These partnerships resulted in both better scientific knowledge about how air pollution is connected to asthma and the placement of air monitors in neighborhoods impacted the most.

In Colorado, the process to choose the five priority air toxics included consulting with multiple stakeholders. A technical working group provided input on which five chemicals should be prioritized from the larger list of .

The working group includes academics, members of nongovernmental organizations such as the – local government and regulated industries, such as the .

There were also opportunities for community participation during public meetings.

At public hearings, community groups like GreenLatinos argued that air toxics because it can .

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Additionally, formaldehyde is emitted in some Colorado communities that are predominantly people of color, according to . These communities are already disproportionately impacted by and .

Other members of the

“One of my patients is a 16-year-old boy who tried to get a summer job working outside, but had to quit because air pollution made his asthma so bad that he could barely breathe,” wrote Logan Harper, a Denver-area family physician and advocate for .

How is air quality protected?

At the national level, the requires that six common air pollutants, such as ozone and carbon monoxide, are kept below specific levels. The act also regulates .

Individual states are free to develop their own regulations, and several, including and , already have. States can set standards that are more health-protective than those in place nationally.

Four of the five chemicals prioritized by Colorado are regulated federally. The fifth chemical, hydrogen sulfide, is not included on the U.S. Environmental Protection Agency’s , but Colorado has decided to regulate it as an air toxic.

State-level regulation is important because states can focus on air toxics specific to their state to make sure that the communities most exposed to air pollution are protected. One way to do this is to place air pollution monitors in the communities experiencing the worst air pollution.

For example, Colorado is placing in locations around the state to measure concentrations of the five priority air toxics. It will also use an existing monitor in Grand Junction to measure air toxics. Two of the new monitors, located in Commerce City and La Salle, began operating in January 2024. The remainder by July 2025.

When Colorado chose the sites, it prioritized communities that are overly impacted by social and environmental hazards. To do this, officials used indexes like the , which combines information about pollution, health and economic factors to identify communities that .

The Commerce City monitor is located in Adams City, a neighborhood that has some of the worst pollution in the state. The site has that are worse than 95% of communities in Colorado.

Air toxics and health

The five air toxics that Colorado selected all have negative impacts on health. Four are known to cause cancer.

Benzene, perhaps the most well known because of its ability to , is one. But it also has a number of other health impacts, including dampening the ability of the immune system and by decreasing sperm count. Benzene and is emitted during oil and gas production and refinement.

and . Symptoms of long-term exposure can include headaches, sore throat, shortness of breath and others. Ethylene oxide is used to sterilize medical equipment, and as of 2024, it was used by four .

Formaldehyde is also , and exposure is associated with . This air toxic is used in the like household cleaners and building materials. It is also emitted by oil and gas sources, .

Hexavalent chromium compounds can cause , as well as such as asthma and rhinitis. A major source of hexavalent chromium is coal-fired power plants, of which Colorado in operation, though these plants are in the next five years. Other sources of hexavalent chromium include .

Finally, long-term exposure to hydrogen sulfide can cause low blood pressure, headaches and a range of other symptoms, and has been such as psychological disorders. Some sources of hydrogen sulfide include .

Jenni Shearston is an assistant professor in the Department of Integrative Physiology.

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