EPA Publishes Final Scope of Risk Evaluation for Octamethylcyclotetrasiloxane

The U.S. Environmental Protection Agency (EPA) announced the release of the final scope of the risk evaluation for octamethylcyclotetrasiloxane on March 7, 2022. The document describes the Agency's risk evaluation plans for octamethylcyclotetrasiloxane, examining factors such as relevant exposures, potentially exposed or susceptible subpopulations, and use conditions. Here we take a closer look at several of these key factors.


Also known as D4 because of its four dimethylsiloxane units, octamethylcyclotetrasiloxane is a volatile, low molecular weight methylsiloxane chemical compound. It is used in a diverse range of industry types, including automobile, construction, electronics, machining, personal care, textile, and more. Often found as an intermediate in silicone polymers, it is used in many consumer and industrial applications.


IUPAC Name2,2,4,4,6,6,8,8-octamethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane
Chemical FormulaC8H24O4Si4
CAS Registry Number556-67-2

Risk Evaluation Final Scope

The risk evaluation encompasses a broad range of use conditions and categories within its scope:

  • Manufacturing -- Including both manufacturing and importing
  • Processing -- Encompassing processing as a reactant, incorporation into formulations and mixtures, and repackaging
  • Distribution in Commerce
  • Industrial Uses -- Including general aircraft maintenance
  • Commercial Uses -- Incorporating adhesives and sealants, automotive products, cleaning products, laboratory chemicals, paints and colorants, and plastic or rubber products
  • Consumer Uses -- Including adhesives and sealants, automotive products, cleaning products, packaging materials, and paints
  • Disposal

Also, as part of the risk evaluation's scope, several exposure types, pathways, and potentially exposed or susceptible subpopulations will be considered by the EPA:

  • Occupational Exposure -- Exposure for workers and occupational non-users will be evaluated in terms of inhalation, ingestion (e.g., dust), and dermal routes (e.g., via manufacturing, use, processing, and disposal)
  • Consumer and Bystander Exposure -- Exposure for consumers and bystanders will be evaluated in terms of inhalation, ingestion, and dermal routes (e.g., via adhesives and sealants, automotive products, cleaning products, laundry and dishwashing products, paints, and plastic and rubber products)
  • General Population Exposure -- Exposure for the general population will be evaluated in terms of inhalation (e.g., ambient air), ingestion (e.g., drinking water, groundwater, breastmilk, fish), and dermal routes (e.g., via contact with water or soil)
  • Environmental Exposure -- Exposure for terrestrial and aquatic receptors will be evaluated
  • Potentially Exposed or Susceptible Subpopulations -- Among the populations that the EPA intends to include in its risk evaluation are women (reproductive age), children, and groups for whom consumption of fish may be high

More detailed information on the final scope of the risk evaluation for octamethylcyclotetrasiloxane may be found by reviewing the document itself.

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