From your deodorant, across the ocean, and back to your plate: siloxanes stay in our environment

Deodorant, shampoo, and other personal care products often contain siloxanes—chemicals that contaminate the environment as soon as they wash down the drain, migrate into fish, and wind up back on your plate. Siloxanes are a group of silicon-based compounds that are used as carriers in personal care products and as intermediates in the production of silicone polymers. This group of chemicals has recently come under scrutiny by environmental chemists, toxicologists, and regulators (such as the Environmental Protection Agency, EPA) because siloxanes easily bind to organic carbon particles and thus easily travel from our homes into the environment, where they become very persistent.

In order to understand how and why siloxanes are so persistent in our environment, we collected seabed sediment and wastewater samples from remote areas of the Arctic and conducted computer simulations to replicate the chemical’s behavior. Our data suggest that the chemical industry substantially underestimates the concentrations of siloxanes in the environment and thus their harm to the ecosystem and human health.

We focused our studies in the Arctic because lower water temperatures are known to increase siloxanes’ ability to bind to organic carbon which increases its ability to travel through the environment and build up in seabed sediment. We collected sediment samples from 1.) a group of Norwegian islands called Svalbard, 2.) Greenland, and 3.) several areas in the Canadian Archipelago. Finally, to estimate the amount of siloxane emissions from products into the environment, we collected wastewater samples from the main settlement in Svalbard called Adventfjorden.

For our study, we used the siloxane concentrations from the samples we collected to validate the computer models that predict emissions and concentrations of siloxanes in the environment. We developed two different models using two different sets of data: one produced by the industry and one produced by our studies. Then we compared the two models to determine which model leads to more accurate computer predictions. Our results suggest that the computer model created with the data measured by the industry is substantially underestimating the amount of siloxanes in the environment and thus their persistence in the environment.

The environmental protection agency of the European Union responsible for the regulation of chemicals, called European Chemicals Agency (ECHA), has recently decided to restrict the presence of one siloxane called D4 in consumer products in the EU. The new policy dictates that D4 shall not be used in consumer products in concentrations equal or greater than 0.1%. This is an important improvement which substantially restricts the amount of siloxanes released to the environment by limiting the amount of siloxanes in personal care products.

Meanwhile, the US Environmental Protection Agency (EPA) announced recently that a draft risk assessment for D4 was prepared by an industry front-group. Their risk assessment was in direct contradiction to risk assessment evaluations conducted by major environmental agencies, such as the European Chemicals Agency, Environment Canada, and the United Kingdom Environment Agency, that all concluded D4 is persistent, bioaccumulative, and toxic. The industry-driven evaluation suffers from deficiencies and miscalculations, such as excluding critical studies in determining D4’s persistence in the environment and its toxicity, and misinterpreting bioaccumulation with biomagnification. As a response to this evaluation, we submitted a comment to the US EPA outlining reasons why this risk assessment should not be accepted.

 Our scientific findings make clear that the siloxane industry is greatly underestimating the amount and persistence of siloxanes in our environment. The EPA needs to reexamine data prepared by independent scientists on siloxanes and conduct a comprehensive study on the risks these chemicals pose to the environment and public health.

About the author

Dimitri Abrahamsson, MSc, PhD is an Environmental Chemist, an all-sorts-chemistry enthusiast, and a postdoctoral scholar with the UCSF Program on Reproductive Health and the Environment. Dimitri received his PhD in Environmental Chemistry from Stockholm University in Sweden. His PhD work focused on the partitioning and persistence of siloxanes in the environment.