The Toxicity of Silicone
June 30, 2020, by Lisa Powers
Silicones are made from silicon, a naturally-occurring element that is abundant in sand. However, in order to make silicon available for industrial processes, it's heated to very high temperatures and reacted with fossil-fuel derived hydrocarbons.(1) This may explain why some people who are sensitive to petrochemicals may react to silicones.
In order to make silicones, silicon is turned into siloxane, through an industrial process. There are a number of different siloxanes. Siloxanes are then bound together into silicones.
Is Silicone Safe?
Silicones are generally considered safe. 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.”(2)
However, some studies are finding that silicones are not completely insert and can release certain toxic substances at low level. Studies are still limited and most focus on a type of siloxane group, cyclic volatile methyl siloxanes (cVMS), which are by-products of silicone manufacturing. The health effects of cVMS are debated but in 2018 the European Chemicals Agency added 3 cVMS (D4, D5, and D6) to their Candidate List of substances that may have serious effects on human health and the environment.
There are few studies that focus on the effects of chemical additives, raw material impurities or fillers that may be present in various silicone products.
Does Silicone Leach into Food and Drink?
Some studies are finding that silicone bakeware can leach into food, particularly at high temperature (above 300°) and into high fat food. For example, migration into meatloaf was higher than into cake.(3,4) Greater migration was found in new, unwashed molds.
One study found that silicone baby bottle nipples do not leach VMS into milk or infant formula after 6 hours.(5) However, a particularly alarming study from 2012 of silicone baby bottles found the presence of phthalates and aldehydes as well as substances related to printing ink.(6) A 2016 study similarly found phthalate migrations from silicone baby bottles.(7) The studies did not assess the migration levels and associated health risks. Further research is needed.
Do Silicones Offgas?
Siloxanes can become gaseous when heated. In one study, 4 of 14 silicone baking molds exceeded Germany’s indoor guide level for cVMS but the health hazard guide level was not exceeded.(8)
Additionally, a possible oxidation product is formaldehyde.(9) Studies of industrial-use silicone have found formaldehyde release at very high temperatures but it is not clear if formaldehyde also releases from silicone consumer products when heated.
Do All Silicones Have the Same Level of Toxicity?
Silicones, like plastics, can include a mix of chemical additives, fillers, and raw material impurities. In general, however, silicones have fewer chemical additives than plastics.
Food-grade silicones that are regulated by the FDA should not contain fillers. Silicone should not change color when it is twisted. If you twist or pinch the silicone and white shows through, the product contains a filler. Also, silicone should not crack or lose elasticity. These conditions indicate the inclusion of fillers in the silicone.
Not all silicone is the same and it is not possible without testing to determine exactly what is in any silicone product. There are hundreds of silicones with hundreds of different formulas. Some, like colorful cookware, may contain various fillers and contaminants that are completely unknown to consumers.
The Bottom Line
There is enough scientific evidence to suggest that silicone is not the totally safe and natural material that some marketers claim it to be. But it is generally safe under many conditions and a safer alternative to most plastics.
Here are some guidelines to safely use silicone products.
Do not heat silicone products above 300°.
Always wash silicone products before use with food or beverages.
If using silicone baby bottles or nipples, make sure they are phthalate-free.*
Choose 100% pure food-grade or medical-grade silicone.
Silicone that is not heated and does not come in contact with food, such as lids, gaskets, bibs, and placemats likely pose no health risk.
*I will look further into the safest choices for baby bottles and nipples.
Sources:
https://www.canada.ca/en/health-canada/services/household-products/safe-use-cookware.html
Ruediger Helling, Anja Mieth, Stefan Altmann, Thomas Joachim Simat. Determination of the overall migration from silicone baking moulds into simulants and food using 1H-NMR techniques. Food Additives and Contaminants, 2009, 26 (03), pp.395-407. 10.1080/02652030802520852 . hal-00577342
Helling R, Kutschbach K, Joachim Simat T. Migration behaviour of silicone moulds in contact with different foodstuffs.Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2010;27(3):396-405. doi:10.1080/19440040903341869
Zhang K, Wong JW, Begley TH, Hayward DG, Limm W. Determination of siloxanes in silicone products and potential migration to milk, formula and liquid simulants. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2012;29(8):1311-1321. doi:10.1080/19440049.2012.684891
Simoneau, Catherine & Van den Eede, Liza & Valzacchi, Sandro. (2012). Identification and quantification of migration of chemicals from plastics baby bottles used as substitutes for polycarbonate. Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment. 29. 469-80. 10.1080/19440049.2011.644588.
Ksenia Groh, Health Risks of BPA-Free Baby Bottles. Food Packaging Forum, Sept. 9, 2016.
Hermann Fromme, Matthias Witte, Ludwig Fembacher, Ludwig Gruber, Tanja Hagl, Sonja Smolic, Dominik Fiedler, Marina Sysoltseva, Wolfgang Schober. Siloxane in baking moulds, emission to indoor air and migration to food during baking with an electric oven. Environment International, 2019, 126, pp.145-151. 1016/j.envint.2019.01.081
Birgit Geueke, Dossier – Silicones. Food Packaging Forum. May, 2015, DOI: 10.5281/zenodo.33522
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