Is Silicone a Plastic?
Good question. Here are some others... Is it a rubber? Is it natural? Is it synthetic? What the heck is it?
And most importantly: Is it safe?
Description and Typical Use: What is silicone?
Technically, silicone is considered part of the rubber family. But, if you define plastics widely, as we do, silicone is something of a hybrid between a synthetic rubber and a synthetic plastic polymer. Silicone can be used to make malleable rubber-like items, hard resins, and spreadable fluids.
We treat silicone as a plastic like any other, given that it has many plastic-like properties: flexibility, malleability, clarity, temperature resistance, water resistance.
Like plastic, it can be shaped or formed and softened or hardened into practically anything. But it is a unique plastic because it is much more temperature resistant and durable than most plastics and has a low reactivity with chemicals. And while water resistant, it is also highly gas permeable, making it useful for medical or industrial applications where air flow is required. It's also easy-to-clean, non-stick, and non-staining, making it popular for cookware and kitchen utensils.
"First of all, silicone is no more "natural" than fossil-based plastic. It is a man-made polymer, but instead of a carbon backbone like plastic, it has a backbone of silicon and oxygen. (Note that I'm using two different words here: silicone is the polymer and silicon, spelled without the "e" on the end, is an ingredient in silicone.) Silicon is an element found in silica, i.e., sand, one of the most common materials on earth. However, to make silicone, silicon is extracted from silica (it rarely exists by itself in nature) and passed through hydrocarbons to create a new polymer with an inorganic silicon-oxygen backbone and carbon-based side groups. What that means is that while the silicon might come from a relatively benign and plentiful resource like sand, the hydrocarbons in silicone come from fossil sources like petroleum and natural gas. So silicone is a kind of hybrid material." (Terry, p. 277)
Thus, while most plastics have a polymer backbone of hydrogen and carbon, silicones have a backbone made of silicon and oxygen, and hydrocarbon side groups - all of which gives them plastic-like characteristics.
Silicone is often used for baby nipples, cookware, bakeware, utensils, and toys. Silicones are also used for insulation, sealants, adhesives, lubricants, gaskets, filters, medical applications (e.g., tubing), casing for electrical components.
Toxicity: Is Silicone Safe?
Many experts and authorities consider silicone completely safe for food use. For example Health Canada states: "There are no known health hazards associated with use of silicone cookware. Silicone rubber does not react with food or beverages, or produce any hazardous fumes."
Scientific American reports that in 1979 the US Food and Drug Administration determined silicon dioxides—the raw material for silicone products—were safe for food-grade applications. However, the first silicone cookware only appeared a decade later (e.g., spatulas) and no follow-up studies were done to assess whether silicone cookware leaches anything potentially harmful.
The fact is, there has not been a lot of research done to date on the health effects of silicone.
Nonetheless, our own research and review of peer-reviewed scientific studies that have been done indicates we should begin to be cautious about silicone.
Here are some highlights:
- Silicones are not completely inert or chemically unreactive and can release toxic chemicals. They can leach certain synthetic chemicals at low levels, and the leaching is increased with fatty substances, such as oils. Evidence of contamination from silicone was found in wine and edible oil foods. Materials such as aluminium, platinum, magnesium and calcium were found to have leached into food when testing was carried out on silicone bakeware. Fluid silicone studies indicated release of siloxanes, one of which - cylcopentasiloxane - is considered toxic and persistent. This siloxane, also known as D5, is used as a softener in cosmetics, and according to the U.S. Environmental Protection Agency may also be carcinogenic. (2005 Report commissioned by the United Kingdom Food Standards Agency: Chemical migration from silicones used in connection with food-contact materials and articles)
- Silicone tubing commonly used for medical applications has been shown to leach several chemicals, including dioctyl phthalate (DOP). (2006 Study in International Journal of Pharmaceutics: Extractables/leachables from plastic tubing used in product manufacturing)
- Silicone intravenous devices have been shown to leach silicone and cause local inflammation. (1999 Study in Archives of Disease in Childhood: Plastic migration from implanted central venous access devices)
- Silicones likely not completely inert and may cause local inflammatione as suggested in this study on the breakdown of silicone joint implants. (1985 Study in Oral Surgery, Oral Medicine, Oral Pathology: Silicone-induced foreign body reaction and lymphadenopathy after temporomandibular joint arthroplasty)
Low recycling rate.
Silicone does not biodegrade or decompose (certainly not in our lifetimes). It is recyclable, but not likely through your local municipal recycling program. You likely would have to take it to a specialized private recycling facility.
Relatively safe. But silicone is not as inert, stable and chemically unreactive as many claim. Use with caution, and if you can find an alternative, use it.
As you can see from our product line, we carry a number of items that contain silicone, usually in the form of seals or gaskets. Silicone has become a standard high quality seal for products requiring a airtight watertight seal, and a suitable alternative has not yet become available.
For now, we are comfortable continuing to carry products that have high quality, food grade silicone parts. We balance the toxicity information stated above with the knowledge that silicone is a high quality, relatively stable material, and leaching of chemicals from other plastics is of much greater concern.
We feel uneasy about silicone cookware. While silicone is durable and has a high temperature resistance, it makes us queasy to be heating food to very high temperatures in a material like silicone which has now been shown to leach and is not completely inert and stable.
If you are going to use silicone, be sure it is high quality, food grade silicone and does not contain any fillers. To test a product for fillers you can pinch and twist a flat surface of it to see if any white shows through. If so, a filler likely has been used. As a result, the product may not be uniformly heat resistant and may impart an odor to food. But most importantly, you will have no idea what the filler is and it may leach unknown chemicals into the food. For all you know, the filler may be a silicone of low quality or not silicone at all.
IMPORTANT NOTES: While we strive to provide as accurate and balanced information as possible on our website, Life Without Plastic cannot guarantee its accuracy or completness because there is always more research to do, and more up-to-date research studies emerging -- and this is especially the case regarding research on the health and environmental effects of plastics. As indicated in our Terms & Conditions, none of the information presented on this website is intended to be professional advice or to constitute a professional service to the individual reader. All matters regarding health require medical supervision, and the information presented on this website is not intended as a substitute for consulting with your physician.
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