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Chemical Regulation

Industry requests safety review of cyclic siloxane

US EPA considers evaluating risks of D4 under the Toxic Substances Control Act

by Britt E. Erickson
April 9, 2020

Chemical structure of octamethylcyclotetrasiloxane (D4).

Octamethylcyclotetrasiloxane (D4), a cyclic organosilicon chemical used as an intermediate to make numerous commercial and consumer products, does not pose risks to human health or the environment, according to a risk assessment conducted by a group of six chemical manufacturers. The companies, represented by the Silicones Environmental, Health and Safety Center (SEHSC), under the umbrella of the American Chemistry Council, submitted their evaluation to the US Environmental Protection Agency earlier this year. The group is requesting that the EPA conduct its own evaluation of the chemical under the Toxic Substances Control Act (TSCA).

Revisions to TSCA enacted in 2016 allow manufacturers to request the EPA to conduct a risk evaluation of certain uses of a chemical that are of interest to the manufacturer. In December 2019, the agency granted requests from industry to evaluate two phthalates—diisononyl phthalate and diisodecyl phthalate. Those evaluations are ongoing. The EPA announced the D4 evaluation request on April 8. If the EPA grants the request, it must then decide whether to use any of the information included in the industry’s evaluation.

D4 is found in a wide range of products, including adhesives, paints, plastics, rubber, automotive parts, soaps, and detergents. The six chemical manufacturers considered these uses in their assessment, as well as uses that are outside the scope of TSCA, such as personal care products and food contact materials, which are regulated by the Food and Drug Administration.

“Based on a thorough risk evaluation SEHSC included in its submission to EPA, the silicones industry continues to believe that no regulatory restrictions on D4 are needed,” Karluss Thomas, senior director of SEHSC, says in a statement.

In January 2019, the European Chemicals Agency (ECHA) announced plans to restrict the sale of products that contain D4 in the European Union, citing the chemical’s persistence in the environment and ability to bioaccumulate in aquatic organisms. ECHA has already restricted D4 in wash-off personal care products, such as shampoos and shower gels, to no more than 0.1% by weight.

The EPA plans to begin accepting public comments on the request to evaluate D4 by June 11. Once the agency publishes that notice in the Federal Register, the public will have at least 45 days to provide input.



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