Q&A - Silicones and the issue of D4/D5

Elkem Silicones produces high-performance silicones with a big range of application possibilities. When producing all of the silicone-based end products modern society is so dependent on, a number of chemical processes are used to create intermediate products, which are then further processed to consumer products. D4 and D5 are two of these intermediate products. Learn more about silicones and the issue of D4/D5 here.

What are silicones?

Silicones are high-performance polymers that can take a variety of physical forms that may range from solids to water-thin liquids and semi-viscous pastes, greases and oils. They have revolutionized thousands of products that add quality to life in terms of performance, comfort and safety. Additionally, they reduce the cost of household and personal care products that consumers use every day.

In the kitchen and throughout the home, silicones are known for their versatility and convenience. Silicone kitchenware is durable, easy to clean, lightweight and stain-resistant. In the household, silicones are used as antifoams in detergents, which enable lower washing temperatures, thereby saving energy. Silicones spread easily and protect surfaces, making them an ideal component for polishes or cleaning agents for household surfaces.

In aerospace applications, silicone products increase the lifespan of vital components, while in railway locomotives they provide tough, long-lasting motor insulation and lubricants for bearings.

They are employed as sealants for windows, as caulking for bridges and bathroom tiles, as coatings to protect facades and historical monuments, as coolants in transformers, as protective encapsulating material for semiconductors in electronics and as foam-control agents in the manufacture of many types of products.

Silicones are also used in a wide range of health care and medical applications. They serve as coatings for hypodermic needles, ensure high oxygen permeability in hydrogel contact lenses, are used in tubing in a wide range of medical devices including insulin pumps, and are particularly suitable in prosthetic devices due to their hypoallergenic properties and a wide range of beneficial physical properties, helping millions of people in their daily lives.

In electronic devices, their high temperature resistance and heat dissemination are essential to provide high-functioning, small devices with the cushioning they need to function.

What are D4, D5 and D6?

Octamethylcyclotetrasiloxane (D4), Decamethylcyclopentasiloxane (D5) Dodecamethylcyclo- hexasiloxane (D6) are cyclosiloxanes, and basic members of the silicone family, serving as the building blocks for many silicones. They are used to create a diverse range of silicone materials (polymers) that provide beneficial characteristics to a wide variety of applications and products, including construction, electronics, engineering, health care and personal care among others. D4, D5 and D6 are most frequently used as raw materials, meaning that the substance is employed in the manufacturing process but is only present at very low (trace) levels in the end products.

Are D4, D5 and D6 safe for the environment and/or human health?

Yes. D4, D5 and D6 are safe for the environment and for human health, when used for their intended purposes. 

Silicones are not new on the market. In fact, they have been used for more than six decades. Still, observed levels monitored in a wide variety of temperatures and surroundings do not give rise to any concern. The many years of use have therefore not led to any environmental concern, and based on the observed data the industry does not expect this to change. Multiple lines of evidence show the environmental levels are not increasing even though uses of silicones have considerably grown over years. 

Large volumes of monitoring data collected by the global silicones industry, academic experts/institutes  and governmental regulatory agencies globally, continue to demonstrate that D4, D5 and D6 are not found at, nor are likely to be found at, levels that pose a risk to the environment. Since they are volatile, the majority of D4, D5 and D6 are released to the atmosphere or will evaporate quickly into the atmosphere if released in other media. Once in the atmosphere, D4, D5 and D6 break down due to natural, physical processes.  

With respect to D5, these conclusions were confirmed by an independent panel of scientists in Canada. The “Board of Review” reviewed all the scientific literature on D5, leading the Canadian Environment Minister to decide that no action was needed to limit the use of the substance. In addition, Environment Canada, having reviewed the environmental data available for D4, has not imposed any product use or concentration restrictions on the use of D4 in any application. Health Canada also has declared D4, D5 and D6 safe for human health.  

These findings were confirmed by Australian regulators for a series of siloxanes, including D3, D4, D5, D6, D7, and cyclomethicone. The Australian assessment concluded: “[t]he direct risks to aquatic life from exposure to these chemicals at expected surface water concentrations are not likely to be significant.” Although most of these substances are known or expected to be persistent in the sediment compartment, Australia, using a risk-based assessment approach, concluded that these silicone materials don’t pose risks to the environment and has not proposed any regulatory restrictions on the use of any of the materials.  

Independent scientists and regulatory agencies have also evaluated how consumers and workers can be exposed to D4, D5 and D6 and concluded that there is no risk to human health. Links to these scientific studies can be found on www.cyclosiloxanes.org/science 

What is Elkem’s position?

The silicones industry continues to study the safety of cVMS and actively collaborates in research programs with academic experts as well as government scientists around the world. The extensive database of health, safety, and environmental data for D4, D5 and D6 continues to support their safe use in a wide range of markets and product applications.

The silicone industry, including Elkem Silicones, is collaborating actively with the regulatory authorities in the different regions, providing data from environmental monitoring studies and additional health and safety research, including a Global Human Health Risk Assessment based on both potential environmental and product-use exposures. The available data supports that:

  • D4, D5 and D6 do not behave as PBTs in the environment because they do not biomagnify up the food chain and cannot reach concentrations in the environment that might cause harm.  Consequently, they should not be regarded or regulated as PBTs.
  •  D4, D5 and D6 may be transported long distances, but break down in the atmosphere, do not back-deposit, and cannot reach concentrations in the environment that might cause harm.  They should not be considered as POPs.
  •  D4, D5, and D6 do not pose a risk to human health or the environment.
  •  D4, D5, and D6 are safe for use in consumer products when those products are used as intended.

The industry will continue to work with regulatory authorities around the world to determine the most appropriate measures to effectively address any potential concerns that may arise. It is also informing the authorities of the many benefits associated with silicones and the socio-economic consequences of disproportionately regulating the substances as PBTs.