On 18 December 2024, the U.S. Environmental Protection Agency (EPA) finalised the designation of five chemicals as High-Priority Substances under the Toxic Substances Control Act (TSCA) and began the yearlong prioritisation process for five additional chemicals. These actions underscore the EPA's commitment to identifying and addressing chemical risks to protect human health and the environment.
High-Priority Substances Designated
The EPA designated five chemicals—acetaldehyde, acrylonitrile, benzenamine, vinyl chloride, and 4,4’-methylene bis(2-chloroaniline) (MBOCA)—as High-Priority Substances for risk evaluation. This marks the conclusion of a 9–12 month prioritisation process.
- Acetaldehyde (CASRN 75-07-0): Used in adhesives and petrochemicals, it is a probable human carcinogen linked to respiratory system irritation.
- Acrylonitrile (CASRN 107-13-1): Found in plastics and paints, this chemical is a probable carcinogen associated with respiratory irritation.
- Benzenamine (CASRN 62-53-3): Used in dyes and resins, it poses risks such as reproductive and blood-related health effects and is a probable carcinogen.
- Vinyl Chloride (CASRN 75-01-4): Widely used in manufacturing polyvinyl chloride (PVC), vinyl chloride is a known human carcinogen and linked to liver toxicity.
- 4,4’-Methylene bis(2-chloroaniline) (CASRN 101-14-4): Primarily used in plastics and resins, this probable carcinogen is associated with genetic damage and other adverse health effects.
The EPA will now evaluate whether these chemicals present an unreasonable risk to health or the environment under their conditions of use. Risk evaluations exclude cost considerations and focus solely on scientific assessments. If risks are identified, regulatory measures will follow.
New Prioritisation Process for Additional Chemicals
In parallel, the EPA initiated the prioritisation process for five new chemicals: benzene, ethylbenzene, naphthalene, styrene, and 4-tert-octylphenol. This process will span 12 months, during which the EPA will gather data and accept public input to determine whether these chemicals warrant High-Priority designations in December 2025.
