Europe Bans Two Cosmetic Ingredients You Didn't Know Are Hazardous

CC BY 2.0. David Blackwell

The chemicals that make your personal products silky smooth are banned from all cosmetics that are washed off after use.

The European Chemicals Agency has announced that the chemicals Octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) will be prohibited in cosmetics intended to be washed off after use, effective in January 2020.

Even the most attentive label readers could be forgiven for not having these two chemicals, known also under their common label ingredient names cyclomethicone (D4) and cyclopentasiloxane (D5), on their list of hazardous chemicals to avoid. And there is a good reason for that: they are not hazardous to humans according to scientific evaluations.

Why Are These Chemicals Banned?

The EWG skin deep database rates D4 at a medium level of '5' and D5 with a '3' currently. There is some evidence in rats that D4 can cause reproductive toxicity, but because the biological action differs in rats, those test results are unlikely to represent a hazard in humans. Both are discussed in the context of endocrine disruption as well but the science is not yet definitive on that topic.

These colorless to white, odorless liquids function perfectly in cosmetic products. They help give them a nice thickness, moisturize, and easily dissolve other ingredients into the smooth, silky cosmetic product people want. But regulators are concerned that they may stick around in the environment - like PCBs, and dioxin, and the fluorochemicals in non-stick products and firefighting foams before them - building up to levels that can cause a hazard to aquatic life.

They Are Still in Use for Other Products

For the time being, the ban is limited to the use of D4 and D5 in wash-off products. D4 and D5 may continue to be used to contribute to fast drying in spray-on sun protection products, under-arm deodorants, and other products while the regulators will continue to study them. They appear also in products outside the personal care sector, such as dry-cleaning products, waxes and polishes, and general cleaning products.

D4 and D5 work well in these products because of their high volatility, which means they evaporate quickly. This means they don't go directly into the water like wash-off products do. But they do go into the air. D4 and D5 have been detected in air at what has been called "alarming" levels, although no one knows if there are any health effects from breathing these chemicals.

In good news, the chemicals break down in the sunlight to harmless bits of silica (sand), carbon dioxide, and water. The siloxane industry has put together a web page on siloxanes to help the public understand the uses of and science of these chemicals. That page mentions D6 also, which is not subject to the current regulatory action but is also under study.

This regulation raises a question that is gaining interest among the people concerned with controlling chemical risks and ensuring sustainability and safety of chemicals: which chemicals are currently "flying under the radar" - having hazards that should be of concern but not yet identified for serious study? In the wake of World Water Day and this announcement from the EU, next week we will write about taking a closer look at what's in our water.