Chemicals from plastic wrap and containers can leach into your food, especially when heated. When looking for food packaging or storage, check out the “chasing arrows” number on the back or bottom of the product.
#4 and #5 are the best. They leach the least and are the most recyclable.
Avoid #7, #6, and #3 if possible.
It’s ok to store your food in 4 and 5, but always heat in a tempered glass or ceramic bowl/plate instead.