The safest materials are usually the best. Silicone, glass, metal, wood, etc. You can check a material's rating on the main product page for any item on Eden. The left hand side has product specs. Where it says "Material" there will be a hyperlink to a page that has information on that material which includes a safety rating. You want to look for 10s if possible. Some 8s and 9s are good as well, like plastic. less