Colorado sets new health standards for cancer-causing ‘air toxics’

Colorado air regulators adopted new safety thresholds for five toxic air contaminants on Friday, marking the latest step in a multiyear regulatory process to protect neighborhoods from pollutants.

The decision comes as the Trump Administration rolls back U.S. EPA rules designed to protect local air quality. Besides seeking to overturn the scientific finding behind federal climate rules, the administration has also announced plans to repeal standards meant to limit air toxics from coal- and gas-fired power plants.

The Colorado Air Quality Control Commission unanimously voted to adopt health-based benchmarks for five chemicals:

• Hydrogen sulfide. A byproduct of industrial livestock and oil and gas operations, known to cause serious neurological issues and death at high exposure levels
• Benzene. A pollutant linked to fossil fuel operations known to cause certain cancers and blood disorders
• Formaldehyde. A volatile compound found in many manufactured wood products. If inhaled for prolonged periods of time, it can exacerbate asthma symptoms and increase cancer risk
• Ethylene oxide. A chemical often used for commercial sterilization known to elevate cancer risk
• Hexavalent chromium compounds. A group of chemicals released from power plants and metalworking operations known to increase lung cancer risk

The rules establish exposure thresholds considered “safe” for each of those chemicals. State regulators, however, won’t begin using the limits for air quality permits and enforcement for at least a year, following final approval from the state legislature.

Debate over the regulations marked a pitched battle between environmental groups and business interests. After a two-day hearing, the commissioners adopted a stricter standard for benzene emissions but opted for a weaker threshold for the four other contaminants, aligning with a proposal from business groups.

That decision disappointed some environmental justice advocates like Patricia Garcia-Nelson, an organizer with the environmental group GreenLatinos. “Unfortunately, the commission once again chose to side with industry,” Garcia-Nelson said.

How Colorado is working to regulate air toxics

The standards nevertheless mark a major milestone in a long-running effort to sharpen state air pollution enforcement.

Under the U.S. Clean Air Act, the federal government sets benchmarks for six so-called “criteria pollutants,” which guide permitting and regulation around common pollutants like smog and carbon monoxide. Similar limits don’t exist for a long list of toxins known or suspected to cause serious health issues like cancer, respiratory problems or birth defects.

Environmental groups claim the lack of standards has left communities vulnerable to dangerous industrial air pollution. After years of lobbying, a coalition pushed a bill through the legislature in 2022, which ordered state regulators to establish health-based thresholds for “up to five” priority air toxins before adopting rules to limit emissions.

Regulators chose the five pollutants in January after another marathon hearing. While many chemicals threaten human health, the state opted to focus on dangerous chemicals linked to industry rather than natural sources like wildfires or vegetation.

That left the much more complicated task of establishing thresholds for different chemicals. To set specific levels, the state set two benchmarks for each pollutant: one based on the odds it would result in cancer following long exposure, and another based on whether it would cause other health issues like nosebleeds or asthma attacks.

Meagan Weisner, a senior scientist for the Environmental Defense Fund, said the commission chose tough benchmarks to protect residents against cancer, ultimately deciding that pollution limits should allow only one in a million people to develop cancer following prolonged exposure.

But environmental advocates were disappointed with the other thresholds meant to protect against non-cancer health issues. Even though the state set a strict benchmark for benzene based on regulations in California, Weisner said regulators chose far less protective concentrations for the four other air toxics.

“It was a mixed bag at the end of the day, but overall positive,” Weisner said.

No clarity on implementation

It’s unclear exactly how state regulators will enforce the standards it approved late last week.

The lack of clarity was a major point of complaint in comments from industry groups. In testimony before the commission, Dave Kulmann, a lobbyist for the Colorado Chamber of Commerce, noted it was impossible to understand the economic impacts of the standards without a clear enforcement plan.

Environmental advocates also want more clarity on Colorado’s plan to enforce the air quality standards. As the federal government scraps its own air quality rules, Weisner said it’s more important than ever for Colorado to develop a clear, rigorous plan to limit pollution from specific industries.

“Maybe it’s going to be done through permitting, but however it happens, it needs to work,” Weisner said. “This is where we lean on the state to ask: what’s going to work to give communities some reprieve from these toxic air contaminants?”