The Environmental Protection Agency is launching a formal review of five highly toxic plastic chemicals, including vinyl chloride, the notorious compound at the center of the East Palestine, Ohio, train wreck fire.

The move could lead to strong limits or bans on the substances.

Vinyl chloride is most commonly used in PVC pipe and packaging production, but is also cancerous and highly flammable. For about 50 years, the federal government has considered limits on the substance, but industry has thwarted most regulatory efforts, hid the substances’ risks and is already mobilizing against the new review.

The step is “one of the most important chemical review processes ever undertaken” by the agency, said Judith Enck, president of Beyond Plastics and a former EPA administrator.

“I applaud the EPA,” she added.

The federal government designates vinyl chloride as a known carcinogen, and the substance is also a neurotoxicant linked to liver damage, permanent changes to bones, and other serious health issues. The EPA is also reviewing acetaldehyde, benzenamine, acrylonitrile and MBOCA, each used in the production of plastic and rubber. All the chemicals are considered to be or are probable carcinogens and linked to other health problems, like anemia, kidney damage and neurotoxicity.

The nation’s use of vinyl chloride drew intense scrutiny after dozens of cars on a Norfolk Southern train derailed and burned in February 2023 in East Palestine. The fire burned near tankers carrying vinyl chloride, and, two days later, fearing a “major explosion”, officials conducted a controlled burn of the chemical as a preventive measure.

When vinyl chloride burns, it creates dioxins, a highly toxic and carcinogenic chemical class that can stay in the environment for generations. The levels of dioxin found in East Palestine in the days after the wreck were hundreds of times greater than the exposure threshold above which the EPA in 2010 found poses cancer risks. Soil and food contamination are considered to be among the most common exposure routes, and the controlled burn’s towering plume also sent dioxins across 16 states.

Vinyl chloride is transported in freight trains that are prone to accidents, and East Palestine was only one in a series of vinyl chloride incidents – experts expect a similar accident. A recent report found more than 3 million Americans live within one mile of railroad tracks on which vinyl chloride is transported.

The Vinyl Institute, which represents vinyl chloride and PVC producers, has downplayed the risk, and labeled the reports “publicity stunts”.

The EPA’s announcement concludes a year-long period in which it gathered comments from industry, public health advocates, labor and others involved in the substances’ use, as is required under the Toxic Substances Control Act (TSCA), which covers the nation’s use of toxic chemicals.

It will spend the next three months gathering more information, and, following that, determine whether to classify the chemicals as high-priority substances under TSCA. That would trigger a formal study to determine if vinyl chloride presents an unreasonable risk to human health or the environment.

That assessment could take three years, and, following that, the EPA would establish new rules. But the action faces an uncertain future – incoming Trump allies have already signaled that they will kill any proposed regulations that have not been finalized.

Opposition from industry against PVC limits is expected to be stiff in part because the substance is used in medical devices, vinyl siding for buildings, drinking water pipes, electrical wiring, household goods like shower curtains and raincoats. Industry groups have already touted the substance’s ubiquity in a statement on the EPA’s announcement.

“[It] presents a welcome opportunity to share our expertise on the many indispensable uses of this highly regulated material,” the Vinyl Institute wrote.