On March 7, 2022, EPA published the final scope of the risk evaluation for octamethylcyclotetra-siloxane (D4). This risk evaluation may affect producers of goods comprised of and/or utilizing the following: adhesives, sealants, synthetic rubber, electrical equipment, appliances, paint, ink/toner, aircraft maintenance components, automotive care components, cleaning products, fabrics/textile products. This is not intended to serve as an exhaustive list. The publication of this risk evaluation originated from a request made by the American Chemistry Council’s Silicones Environmental, Health, and Safety Center (SEHSC). The scoping document addresses conditions of use, exposures, hazards, and potentially exposed or susceptible subpopulations.
Conditions of Use
Conditions of use for D4 risk evaluation can be sub-divided into the following life cycle stages: manufacturing, processing, distribution in commerce, industrial use, commercial uses, consumer uses, and disposal. EPA’s evaluation will address each of the aforementioned life cycle stages. Notably, processing is the most nuanced of these stages. Specifically, the processing stage is comprised of three subcategories: processing as a reactant; incorporation into formulation, mixture, or reaction product; and repackaging.
In the forthcoming risk evaluation, EPA will evaluate human and environmental exposures as well as releases into the environment resulting from these conditions of use identified in the scoping document. The evaluation will contemplate the physical and chemical properties of D4; environmental fate and transport processes, exposure pathways, and potential human and environmental receptors; releases to the environment; environmental exposures (both aquatic and terrestrial); occupational exposures; consumer exposures; and general population exposures.
Regarding environmental hazards, EPA will assess the following potential hazard effects of D4 to aquatic and terrestrial organisms including: absorption, distribution, metabolism, and excretion (collectively referred to as “ADME”), developmental, gastrointestinal, mortality, neurological, nutritional, metabolic, reproductive, and respiratory. The scoping document notes that D4 can degrade into dimethylsilanediol (DMSD) under certain environmental conditions. Accordingly, EPA has indicated that it may factor toxicity information regarding DMSD into its risk evaluation.
With respect to human health hazards, EPA intends to examine the relation of D4 exposure to the following: ADME, cancer, endocrine, gastrointestinal, hematological, immunology, hepatic, mortality, neurological, nutritional/metabolic, ocular/sensory, renal, reproductive, developmental, respiratory, and skin/connective tissue. The scope of EPA’s assessment of the human health hazards of D4 may also contemplate hazards associated with exposure to DMSD as mentioned above.
Potentially Exposed or Susceptible Subpopulations (PESS)
In accordance with the requirement of TSCA section 6, the following groups will be considered potentially exposed or susceptible subpopulations in the D4 risk evaluation: children, women who may become pregnant, workers, occupational non-users (ONU), consumers, bystanders, fence line communities, and indigenous and native populations. Environmental justice considerations will also be factored into the PESS analysis. These considerations will follow the best practices discussed within EPA’s Technical Guidance for Assessing Environmental Justice in Regulatory Analysis.