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Chemical Regulation

US EPA to evaluate cyclic siloxane

by Britt E. Erickson
October 9, 2020 | A version of this story appeared in Volume 98, Issue 39

Chemical structure of D4.

The US Environmental Protection Agency has agreed to evaluate the risks of octamethylcyclotetrasiloxane (D4), a cyclic organosilicon chemical used in numerous commercial and consumer products. Earlier this year, six chemical manufacturers represented by the American Chemistry Council’s Silicones Environmental, Health and Safety Center (SEHSC) asked the EPA to conduct the assessment under the Toxic Substances Control Act. The manufacturers provided the EPA with their own risk assessment of D4, showing no unreasonable risks to human health or the environment. D4 is used as an intermediate in making adhesives, paints, soaps, and many plastic and rubber products. It is also found in personal care products and food packaging, which are regulated by the Food and Drug Administration under a different law. “Based on SEHSC’s thorough risk evaluation submitted to EPA, the scientific evidence continues to confirm that no regulatory restrictions on D4 are warranted,” Karluss Thomas, senior director of SEHSC, says in a statement. Because of the chemical’s persistence and ability to bioaccumulate in aquatic organisms, the European Union restricts D4 to no more than 0.1% by weight in personal care products that are washed off in normal use.


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