Peer Review of the Draft Risk Evaluation for Octamethylcyclotetrasiloxane (D4)
Octamethylcyclotetrasiloxane (D4) is undergoing risk evaluation under the Toxic Substances Control Act.
D4 is a colorless, oily liquid with an annual total U.S. production volume between 750 million and 1 billion pounds. The primary uses for D4 are to make other silicone chemicals with commercial uses including, but not limited to, adhesives and sealants, automotive care products, paints and coatings, and other plastic and rubber products.
Upcoming Meetings
EPA has rescheduled the planned November 18, 2025, preparatory virtual public meeting of the Science Advisory Committee on Chemicals (SACC) to December 1, 2025. Register for the December 1, 2025 preparatory virtual meeting here.
To present oral comments during the preparatory meeting, you must register by noon (12:00 p.m. EST) on November 24, 2025, and submit a written version of your oral comments by noon (12:00 p.m. EST) on November 28, 2025.
The December 2-5, 2025, SACC peer review meeting to discuss the D4 draft risk evaluation and technical support documents has not been rescheduled at this time. These meetings could be further postponed pending prolonged government shutdown. Register for the December 2-5, 2025, SACC peer review meeting here.
Peer Reviewers
On September 10, 2025, EPA requested nominations of scientific and technical experts to be considered as ad hoc reviewers assisting the SACC with this peer review. On October 9, 2025, EPA requested comments on qualified and available candidates under consideration to serve as ad hoc reviewers assisting the SACC with this peer review. Biographies of the interested and available candidates are posted in the docket EPA-HQ-OPPT-2025-1610 on www.regulations.gov. On October 29, 2025, EPA posted in the docket the biographies of the ad hoc reviewers who have been selected for this peer review based on the scientific expertise needed to address the SACC peer review charge and to obtain a breadth and balance of different scientific viewpoints across the SACC and ad hoc peer reviewers.
For additional information, contact the Designated Federal Official, Dr. Alaa Kamel at kamel.alaa@epa.gov.