Silicone bakeware –While silicone is safe for low-heat uses like microwaving, boiling, and dishwasher cleaning, it is not ideal for high-heat baking. Repeated exposure to baking temperatures (typically 300–450°F) can cause lower-quality silicone and fillers to break down over time, releasing small amounts of chemicals into food. For this reason, silicone bakeware is not recommended for regular oven use.

Silicone baking mats – Same concern as silicone bakeware; coatings and fillers can break down at high temperatures over time.

Ceramic or stoneware of unknown quality – Glazes may contain lead or cadmium, especially in older or imported pieces. Even “food-safe” glazes can leach trace metals under high heat or acidic foods.

Non-stick coatings on sheet pans – PTFE or ceramic-based nonstick layers can degrade at baking temperatures, releasing fumes or micro-particles.

Decorative foil liners – Often dyed or printed with metallic or colored coatings; under high heat and moisture, these finishes can transfer chemicals or metals into food.

Aluminum foil – Bare aluminum can react with acidic or salty foods during baking, transferring aluminum into food; nonstick foil also carries a chemical coating.

Bare aluminum bakeware (muffin tins, sheet pans, cake pans) – Direct contact with batters or acidic ingredients can cause aluminum to leach; anodized aluminum is more stable but still not ideal at high heat or with acidic foods.