The U.S. Environmental Protection Agency (EPA) has proposed to designate five chemicals as high-priority substances including Vinyl Chloride, the chemical involved in the Norfolk Southern train derailment in East Palestine.

Vinyl Chloride is used in the manufacturing and processing of plastic materials. According to the EPA, it is included in polyvinyl chloride (PVC), plastic resins, and other chemicals used for pipes and insulating materials.

The chemical is a known human carcinogen, a substance that can cause brain, liver, and lung cancer in those exposed to it.

According to the EPA, short-term exposure can cause dizziness, nausea, and skin and eye irritation. Long-term the substance can damage genetic material in cells, leading to health impacts.

The EPA raised concerns about vinyl chloride in the 1970s, using the health impacts of the substance as an example in the Toxic Substances Control Act.

Prioritization is the first step under the EPA's authority to regulate existing chemicals. The substances will have risk evaluations to determine if they pose an unreasonable risk to human health or the environment. The EPA is required to complete the evaluations within three and a half years.

The EPA proposed four other chemicals for high-priority designations - acetaldehyde, acrylonitrile, benzenamine, and 4,4' - methylene bis.

All five chemicals are used to make plastic and have been linked to cancer.