What: On September 17, 2025, the U.S. Environmental Protection Agency (EPA) published the draft risk evaluation for Octamethylcyclotetrasiloxane (Cyclotetrasiloxane, 2,2,4,4,6,6,8,8- octamethyl-) (D4).
Why: D4 is a colorless, volatile, oily liquid primarily used to make silicone chemicals. D4 commercial uses include adhesives and sealants, automotive care products, paints and coatings, and other plastic and rubber products. D4 is also used as an ingredient in consumer products such as cosmetics, medical devices, and food contact materials.
Under the Toxic Substances Control Act (TSCA), the purpose of a risk evaluation is to determine whether a chemical substance presents an unreasonable risk of injury to human health or the environment. For D4, EPA used the best available science to preliminarily determine, based on the weight of scientific evidence, that D4 poses an unreasonable risk to human health and the environment, driven primarily by certain conditions of use analyzed in the draft risk evaluation.
Action: Comments are due November 17, 2025. Additionally, the EPA will hold a virtual public meeting on December 2-5, 2025, for the agency’s Science Advisory Committee on Chemicals (SACC) to discuss the draft risk evaluation and technical support documents for D4. EPA will also hold a preparatory virtual public meeting on November 18, 2025, for the SACC and the public to consider and ask questions regarding the scope and clarity of the draft charge questions. Registration instructions for the virtual preparatory and peer review meetings will be announced on the SACC website approximately one month before each meeting.
FEDERAL REGISTER NOTICE:
DRAFT D4 RISK EVALUATION:
Risk Evaluation for Octamethylcyclotetrasiloxane (D4)
MEETING ANNOUNCEMENTS:
Peer Review of the Draft Risk Evaluation for Octamethylcyclotetrasiloxane (D4)
CONTACT: Nick Goldstein
EMAIL: nick.goldstein@sba.gov
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