The silicone-making compound, used in electronics, adhesives, and personal care products, is linked to fertility risks and harm to fish and other species.
U.S. regulators said that D4, a chemical used to make silicone goods from solar panels to cosmetics, may harm women’s fertility and damage aquatic and land animals.
The Environmental Protection Agency’s (EPA) Sept. 17 draft risk evaluation concluded that D4—formally known as octamethylcyclotetrasiloxane—presents “unreasonable” risks to human health in almost two dozen uses and to the environment in seven cases. The agency found no such risk in 37 other applications.
EPA said the human health concerns are driven mainly by worker exposures in 23 uses, such as manufacturing D4, processing it into adhesives and sealants, and applying D4-containing paints and coatings in industrial and commercial settings.
The agency’s draft risk evaluation points to reproductive toxicity studies as the hazard driver for the human health finding. In the document, EPA notes that D4 exposure is linked to adverse reproductive outcomes in women.
While one consumer use—inhalation of fumes or skin contact with paints and coatings—was also flagged as hazardous, the agency determined that for the general population, no uses of D4 “significantly contribute to unreasonable risk.”
The agency noted that its findings did not assume the use of personal protective equipment, though it said that equipment like respirators and gloves could mitigate risks.
Notably, EPA’s evaluation does not cover D4 in cosmetics, medical devices, or food-contact materials, since those applications fall under other federal laws. However, the agency pointed to a 2008 assessment in Canada, which found that D4 is not harmful to human health at levels of exposure found in personal care products. The European Chemicals Agency has labeled D4 a “substance of very high concern” due to its persistent, bioaccumulative, and toxic properties.
EPA’s review also highlights environmental dangers, with seven uses tied to acute and chronic exposures that could harm fish, benthic invertebrates, and other wildlife. The agency said it expects the main environmental pathway to be releases of D4 into surface waters and sediment, where the compound’s persistence raises concerns about long-term ecological impacts.
By Tom Ozimek
