Using an old, rusted cookie sheet as a cutting board is not recommended. There are several reasons why it may not be safe:
Rust: Rust can contain harmful bacteria and other contaminants that can contaminate your food. When using a rusted surface as a cutting board, these contaminants can transfer to the food and potentially cause foodborne illnesses.
Surface damage: Rusted cookie sheets often have rough and uneven surfaces. This can make it difficult to clean thoroughly, leaving behind food particles and bacteria that can contaminate future food preparations.
Chemicals: The rust on the cookie sheet may contain toxic substances that can leach into your food when in contact. This can pose health risks if consumed.
Stability: Cookie sheets are typically not designed to provide stability and grip while cutting. They are thin and can easily slide or move around, increasing the risk of accidents and injuries while using them as a cutting surface.
It is always best to use proper cutting boards that are designed for food preparation. Cutting boards made of plastic, wood, or bamboo are commonly used and are easier to clean, maintain, and provide a safe surface for cutting food.