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Is cooking with silicone safe?

Risks of Silicone Bakeware

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First published: 03. Feb.2025

Chemicals in the Kitchen

Silicone rubber is a relatively cheap product that is flexible, non-stick, grease and water repelling, and heat resistant, features that make it ideal for making kitchen products like molds for cakes, cookies, muffins, sheets, spatulas, scoops, etc.

However, silicone rubber can also contaminate your food with unwanted hazardous chemical compounds.

This article explores the health risks of silicone rubber kitchen utensils and cookware.

In this Article (Index)

colorful silicone cupcake molds
Is cooking with silicone molds safe? Chemicals in the Kitchen. Source (License)

What is Silicone Rubber?

Silicone is used to manufacture household utensils, bakeware, and cookware. They are found in every kitchen as reusable muffin cups, ice trays, baking sheets, and cake molds. Colorful and practical.

Silicone rubber is flexible; it has a non-stick surface and is easy to clean. It is freezer-safe and can be cooked in the oven up to 428 °F (220°C).

Silicone rubber isn't a thermoplastic like PET, polypropylene, or polyethylene that can be ground and melted for multiple reuse when recycled. It is a type of synthetic rubber. But, unlike the rubber in your car's tires which are made from crosslinked molecules formed with a backbone of carbon (C) atoms bonded to each other (C—C), silicone is made of another element, silicon (Si) which forms molecules with a silicone - oxygen (O) backbone. The Si—O bond known as the siloxane bond is much stronger than the carbon-carbon bond and resists higher temperatures before breaking. Regular rubber would burn at 175-250 °F (80-120 °C).

Silicone cookware is made by mixing liquid silicone prepolymers with a platinum (Pt) catalyst that accelerates the bonding ("curing") process. One prepolymer has a vinyl group linked to the silicone backbone, the other has hydrogen atoms. Both groups, vinyl and hydrogen link up, crosslinking the prepolymers into a rubbery mesh. The process is known as addition curing or platinum-catalyzed hydrosilylation.

Different additives and fillers are mixed into the prepolymers for color, resistance to ultraviolet light, and texture, and the liquid is poured into molds where it takes its final shape and cures.

Food-grade and Medical-grade silicone rubbers should contain low levels of toxic chemicals, however, some residual products like siloxane oligomers and 2,4-dichlorobenzoic acid present in silicone may be released from the cured silicone rubber and migrate into food in the presence of acidic or fatty ingredients.

As the silicone bakeware ages, after repeated cooking and washing cycles, it degrades, becomes tacky (sticky), and loses color. Time to scrap it.

But not all silicone cookware is the same, different manufacturers may use different grades of silicone, and cheaper additives (pigments, fillers, binders). So buying from a reputable supplier is a safe option to protect your health.

Chemicals in the Silicone migrate into the food

Several studies have tested actual molds purchased at retailers or online and subjected them to migration tests that replicate normal kitchen use (repeated heating at normal oven baking temperatures, with fatty or acidic mixes that simulate a normal cake mix).

The results are not encouraging, chemicals migrate from the silicone rubber into the food baked in them. Below we mention some of these tests.

Testing the Molds

European Consumer Organization (BEUC) 2022 study

On December 6, 2022, The European Consumer Organization (BEUC), (5) published the findings of ten of its country members on the risk of chemicals migrating from silicone molds into the food baked in them.

Migration is when chemicals leach or are released from a product and move into the surroundings, in this case, from the mold into the food.

A total of 44 silicone kitchenware products regularly sold in the European Union were sampled and subjected to migration tests. 23% of them released chemicals in levels exceeding 30 mg/kg or did so in increasing amounts over time.

82% of the samples contained low levels of chemicals that are classed as substances of concern like hormone disruptors, carcinogenic (cancer-producing), mutagenic (mutation-causing), or reprotoxic (harm human reproduction).

Even though the EU legislation on food contact materials requires that any substance that comes into direct or indirect contact with foods be inert and not release substances into the food, silicones are not subjected to detailed rules. Only 5 member states have enacted national legislation on silicone food contact, none of which address the release of contaminants.

BEUC noted that "many of the products purchased through online marketplaces such as AliExpress or Amazon were among the worst performers in the test," a finding echoed in another study, also published in 2022.

Danish Consumer Council 2022 Study

A test sponsored by the Danish Consumer Council published in 2022, (1) tested 18 different silicone baking molds and found "that they can release problematic chemicals into the food."

  • 9 of these silicone molds released larger amounts of chemicals and/or had a higher release of the problematic siloxanes.
  • 5 out of these 5 molds were purchased in "online marketplaces Aliexpress, Amazon and Wish. Therefore, we do not recommend buying baking molds and other kitchen equipment outside the EU."
  • They tested each mold 3 times, while some released fewer chemicals during each test, some molds released more chemicals each time they were tested, the authors concluded "that the material is not stable and the baking form is not suited for repeated use. There is a risk that it will release more and more chemicals into the food over time."

Cocktail Effect

The authors were concerned about the health effects caused by exposure to these chemicals over long periods.

Even though the exposure to chemicals leached from a silicone mold into a muffin may be minute, and harmless, the cumulative exposure to chemicals from different sources day after day can be problematic.

The Chemicals in our Kitchenware

So, how do these chemicals get into the silicone rubber in the first place?

As silicone rubbers contain residues of the additives, monomers, and a catalyst used to produce them, and these can move freely through the lattice formed by the rubber, they can migrate into the food cooked in silicone rubber molds.

The silicone rubber contains silicone monomers, most of which react, crosslinking to form the rubber matrix, but part of this silicone does not react and bond to the rubber lattice, it is free to move. Other silicone molecules are altered during curing, and don't crosslink either, they become cyclic siloxanes. Some of them are volatile, and heat causes them to move quickly out of the rubber. Finally, the additives used in the molding process like the platinum catalyst, lubricants, surfactants, pigments, antioxidants, Ultra-violet light filters, etc., are present in the rubber, and they can also leach out of the product and migrate into the food baked in it.

Fats and oils, or acids used as cooking ingredients can promote the migration of chemicals.

Release of problematic chemicals

The EU has listed problematic chemical substances of very high concern (SVHC) and it includes these cyclic siloxanes.

The Danish test (1) reported that silicone molds release three of these listed cyclic siloxanes when they are heated: Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6).

D4 is suspected to damage fertility, D5 is an endocrine disruptor (it alters hormones), and D6 may have effects on the liver and thyroid gland.

The test also detected another hormone-disrupting chemical, ethyl hexyl salicylate. One mold released low levels of dibutyl phthalate (linked to cancer and reproductive harm), and another one released benzophenone, a UV filter which is a suspected endocrine disruptor and carcinogen.

Reputable manufacturers resort to a heat treatment called post-curing, by which the rubber molds are heated at 392 °F (200 °C) for 4 hours to allow the volatile organic compounds like these siloxanes, to move out of the rubber and be released into the air. This heat treatment helps them meet the requirements set by the non-mandatory German Bundesinstitut für Risikobewertung (BfR standard, 2007) "Recommendations on Food Contact Materials". (3)

However, since it isn't a mandatory requirement, low-cost suppliers (selling online) don't use a costly post-curing treatment and sell goods with a high content of VOCs.

A 2022 study (3) tested four molds to verify migration and volatile organic compounds (or VOCs), harmful chemicals that are let off when the silicone molds heat up. Two were high-quality, expensive, molds that were post-cure heat treated by the manufacturer; the other two were cheap products with no indication of post-cure treatment. The study found that "molds from lower quality manufacturers showed a loss of VOCs that exceeds the recommended value... established by BfR." They also found migration of twelve cyclosiloxanes (from D4 to D15) and one linear siloxane (L7). However, the two molds that had been treated after curing were within the limits set by law (10 mg/dm2). While the two "cheap" molds exceeded the legal migration limit.

The test also found other chemicals used as additives in silicone rubber (antioxidants, lubricants, surfactants, etc) that migrated into the food such as naphthalene, 1,1-biphenyl, 2-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, dodecyl acrylate, hexadecanoic acid, and eicosane.

Regarding the VOCs, a 2019 trial (2) analyzed indoor air during baking with 14 new silicone molds. It reported the presence of volatile methylsiloxanes (VMS) in the indoor air during baking, which partially exceeded the indoor guidelines with the number of particles increasing from 7,300 to 140,000 particles/cm3 during baking. 4 of the molds exceeded the German indoor precaution guide value for cyclic VMS. The authors suggest that "silicone moulds should be used only after precleaning and while strictly following the temperature suggestions of the producers. In the next section, we will look at some tips for using silicone cookware safely.

Tips for Using Silicone Kitchenware

The Danish consumer study (1) gives the following tips for safe use of silicone bakeware:

  • Don't buy them online (unknown origin), buy them from well-known retailers.
  • Only buy products that have the maximum temperature clearly written on them.
  • Check that your cooking temperature is suitable for the temperature range of your mold.
  • Wash the mold thoroughly before using it for the first time. Then heat the empty mold in an oven at 392 °F (200 °C) for a few hours. This pretreatment removes chemicals from the mold, especially the water-soluble ones and the volatile compounds.
  • Keep the molds away from the walls and top of your oven (hot spots).
  • When they show signs of wear, discard them.

How you cook may also be important according to a 2020 study (4) that reported that baking cakes with olive oil is better than peanut and corn oil which significantly increased the amounts of D4, D5, and D6 migration into food. It also found that adding milk and milk products decreased the levels of these three cyclic siloxanes.

Consider using glass or metal molds to avoid interacting with harmful chemicals. By the way, silicone is not recyclable.

Closing Comments

Polymers both rubbers and plastics are present everywhere in our daily lives, but not only in the gadgets we use, they are in the air we breathe, and the food we eat, they are part of our bodies, as tiny chunks of plastic called microplastics inside our cells.

Perhaps it is time to take action and go back to the basics, metal, glass, wood, clay-based ceramics, paper, cardboard, and skip the polymers.

References and Further Reading

(1) Lars Andresen og Katja Ravn, (2022). Silicone moulds can release unwanted chemicals into the food. Danish Consumer Council THINK Chemicals, 15. november 2022

(2) Hermann Fromme et al., (2019). Siloxane in baking moulds, emission to indoor air and migration to food during baking with an electric oven. Environment International, Vol 126, pp 145-152, ISSN 0160-4120, https://doi.org/10.1016/j.envint.2019.01.081

(3) Esther Asensio, Joaquin Uranga, Cristina Nerin, (2022). Analysis of potential migration compounds from silicone molds for food contact by SPME-GC-MS. Food and Chemical Toxicology, Vol 165, 113130, ISSN 0278-6915, https://doi.org/10.1016/j.fct.2022.113130

(4) Yi-Qi Liu, Wen-Wen Yu, Huan Jiang, Gui-Qin Shang, Shao-Fu Zeng, Zhi-Wei Wang, Chang-Ying Hu, (2020). Variation of baking oils and baking methods on altering the contents of cyclosiloxane in food simulants and cakes migrated from silicone rubber baking moulds. Food Packaging and Shelf Life, Vol 24, 100505, ISSN 2214-2894, https://doi.org/10.1016/j.fpsl.2020.100505

(5) BEUC , (2022). Half baked: EU food packaging laws need a rethink to keep consumers safe. (December 6, 2022)

About this Article

Is cooking with silicone safe?, A. Whittall

©2025 Fit-and-Well.com. First Published: 03.Feb.2025. Update scheduled for 03.Feb.2027. https://www.fit-and-well.com/fitness/silicone-kitchen.html

Tags: silicone, microplastics, chemicals, risks

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