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 will hold a virtual public meeting on December 2-5, 2025, for the 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.
To have comments on the draft risk evaluation, technical support documents, and charge questions be considered by the SACC during the preparatory and peer review meetings, written comments should be submitted by November 4, 2025, to the peer review docket EPA-HQ-OPPT-2025-1610 on www.regulations.gov.
Register for the November 18 preparatory meeting here. To present oral comments during the preparatory meeting, registration should be completed by 12:00 p.m. ET on November 11, 2025, and a written version of oral comments should be emailed by 12:00 p.m. ET on November 14, 2025, to the Designated Federal Official (DFO) at kamel.alaa@epa.gov. For attendees not making oral comments, registration will remain open through the end of this meeting on November 18, 2025.
EPA will publish a registration link for the December SACC meeting on this page approximately one month prior to the meeting. To present oral comments during the peer review meeting, registration should be completed by 12:00 p.m. ET on November 25, 2025, and a written version of oral comments should be emailed by 12:00 p.m. ET on November 28, 2025, to the DFO at kamel.alaa@epa.gov. For attendees not making oral comments, registration will remain open through the end of this meeting on December 5, 2025.
Peer Reviewers
On September 10, 2025, EPA called for 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 called for comments on qualified and available candidates under consideration to serve as ad hoc reviewers assisting the SACC with this peer review. Comments must be submitted on the peer review docket EPA-HQ-OPPT-2025-1610 on www.regulations.gov by October 23, 2025. When providing comments, do not submit any information you consider to be confidential business information or other information whose disclosure is restricted by statute. Members of the public are advised that personal contact information, if included in any written comments, may be posted on the internet. The final selection of the ad hoc peer reviewers will depend upon the scientific expertise needed to address the SACC peer review charge and obtaining 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.