EPA Classifies Five Substances as High-Priority for Risk Evaluation Under Toxic Substances Control Act

On December 18, 2024, the U.S. Environmental Protection Agency (EPA) announced its decision to formally classify five known or suspected carcinogens as High-Priority Substances (HPS) for risk evaluation under the Toxic Substances Control Act (TSCA). Additionally, the Agency revealed the launch of a 9- to 12-month statutory process to prioritize another set of five chemicals under TSCA, aiming to determine whether they should also undergo risk evaluations.

EPA Begins Risk Evaluations for Five Chemicals

In July 2024, EPA proposed 5 chemicals for risk evaluation, releasing significantly more data earlier than previous efforts, providing the public better opportunities for input. This streamlined approach builds on improvements made over the past year, including advanced software for earlier data reviews, enhanced systematic review methods recommended by the Scientific Advisory Committee on Chemicals (SACC), and interactive tools to improve transparency.

EPA will now begin evaluating whether these substances pose unreasonable risks to health or the environment under their current uses. If risks are identified, the Agency will promptly initiate management measures to address them. The chemicals are:

• Vinyl chloride (CASRN 75-01-4), widely used in producing plastics such as PVC, plastic resins, and other materials for pipes, insulation, and consumer goods, poses significant health risks. Exposure can cause liver toxicity and is linked to cancer, as it is a known human carcinogen.
• Acetaldehyde (CASRN 75-07-0), widely used in manufacturing adhesives, petrochemicals, and intermediates for packaging and construction materials, poses health risks, including respiratory irritation. It is also a probable human carcinogen.
• Acrylonitrile (CASRN 107-13-1), widely used in producing plastics, paints, petrochemicals, etc., poses health risks, including respiratory irritation and is classified as a probable human carcinogen.
• Benzenamine (CASRN 62-53-3), widely used in manufacturing dyes, pigments, plastics, and chemicals, poses potential health risks including blood disorders, reproductive harm, and fetal development issues. It is also classified as a probable human carcinogen.
• 4,4’-methylene bis(2-chloroaniline) (MBOCA) (CASRN 101-14-4), widely used in manufacturing rubbers, plastics, and resins, is classified as a probable human carcinogen. Studies show it can damage genetic material in cells, posing significant health risks, especially to infants and children.

Prioritization Process Initiated for the Next Five Chemicals:

• Benzene (CASRN 71-43-2): Used in manufacturing adhesives, petrochemicals, plastics, and consumer products such as paints and fuels. Benzene is a known human carcinogen linked to leukemia and immune system impacts.
• Ethylbenzene (CASRN 100-41-4): Found in petroleum, paints, adhesives, and plastics. Exposure may harm the liver, kidneys, and hearing and is a probable carcinogen linked to lung and kidney tumors in animals.
• Naphthalene (CASRN 91-20-3): Used in paints, fuels, and metal products. It may cause red blood cell damage, liver and lung tissue harm, and is a probable carcinogen linked to lung and nasal tumors.
• Styrene (CASRN 100-42-5): Found in adhesives, plastics, toys, and construction materials. Styrene may lead to hearing loss, memory issues, miscarriages, and tissue damage. It is a probable carcinogen linked to lung tumors in animals.
• 4-tert-Octylphenol (CASRN 140-66-9): Used in plastics and automotive products. Exposure may cause kidney inflammation and reduced sperm count, potentially affecting fertility.

EPA has opened a 90-day public comment period, seeking information on the uses, hazards, exposures, and potential risks of the five chemicals under review. Comments are due by March 18, 2025.