Silicone bakeware can release chemical compounds into food and air during baking, with children showing the highest modeled exposure. Digest
Silicone bakeware has become a kitchen staple for its flexibility and nonstick surface, yet little is known about how much of its chemical ingredients migrate into food or the air when heated. Scientists at Health Canada set out to fill that gap by measuring how cyclic siloxanes, chemical compounds that can remain as residual substances in silicone baking forms after the manufacturing process, behave during typical baking conditions.
The team tested 25 new silicone baking products bought in Canada, including cupcake molds, loaf containers, and cookie sheets. Each was baked at 177°C (338°F) for one hour inside a small, ventilated room, using a mixture of oil and sand to mimic food with a moderate fat content. Air samples were taken before, during, and after baking to track volatile chemicals, while the simulated food was analyzed to quantify the migration of different cyclic siloxanes into it. Using the measured concentrations together with age-specific breathing rates, food intake, and body weights, the researchers also modeled potential exposures for different age groups.
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The results revealed that new silicone bakeware can emit and transfer measurable amounts of cyclic siloxanes during baking:
- Every product contained cyclic siloxanes, with twenty-five types (D3–D27) identified and quantifiable forms (D4–D16) totaling about 680 to 4,300 micrograms per gram of silicone.
- After one bake, the simulated food contained an average of around 105 micrograms per gram of siloxanes, and molds with larger contact area released the most.
- Indoor air samples collected during baking showed sharp spikes in siloxane levels, averaging about 646 micrograms per cubic meter during the hour of heating, and returned close to background levels once baking ended.
- Heavier forms of siloxanes were the main contributors to food-based exposure (D11–D16) and also to air concentrations (D7–D9).
- When a cupcake mold was reused nine times, emissions to air and migration into food had already dropped by about 95 percent after the third cycle, suggesting that most releasable material is lost early on.
- Based on the exposure modeling, a one‑year‑old child would have the highest exposure per kilogram of body weight on baking days for inhalation, while children aged 4–8 years would have the highest dietary intake.
Lighter siloxanes such as D4–D6 are relatively well characterized and can affect the liver and lungs at high exposures. In contrast, the heavier forms remain largely untested for toxicity, making them a greater uncertainty.
High-quality, food-grade silicone is manufactured in a way that minimizes cyclic siloxane residuals, yet even high-quality products can release small amounts during initial use. A noticeable chemical or "plastic" odor signals the release of cyclic siloxanes and other volatiles. Because emissions and migration dropped sharply during the first few baking cycles in the study, preheating or using new bakeware several times in a well-ventilated room before using them with food can substantially reduce exposure.
The study used a single temperature and baking duration and relied on an oily food simulant rather than real foods, which limits how closely these results reflect typical household baking. Still, it highlights the importance of careful choice and use of everyday products to reduce exposure to potentially harmful chemicals. To learn more about everyday sources of invisible pollutants and practical ways to reduce exposure, listen to my episode on microplastics.