"One of the prohibited substances can cause cancer; new state law forced operators to identify chemicals."

"Colorado oil and gas companies used toxic chemicals prohibited under state law in operations involving dozens of wells on either side of the Rocky Mountains over at least the last 18 months, a Capital & Main investigation found.

Disclosures to the state’s fossil fuel regulator showed operators combined banned substances with water, sand and other chemicals as part of a process known as hydraulic fracturing, or “fracking.” Companies pump this mixture down a well extending thousands of feet underground to crack shale and release oil and gas.

One of the banned chemicals, known as 1,4-Dioxane, was determined by the U.S. Environmental Protection Agency to present an “unreasonable risk to workers and the general population.” The agency found ingesting or breathing it “can cause cancer, liver toxicity, and adverse effects to nasal tissue.” That substance, and a second also prohibited under state law, 2-Butoxyethanol, are used in fracking fluid. A third, FD&C Blue No. 1, was found by companies and state regulators to have been erroneously listed on disclosure forms."

Jennifer Oldham reports for Capital & Main October 17, 2025. [2]