Exposing plastics to heat or acids can enhance the leaching of chemicals from containers into foods. Nutrition Diva considers the safety of putting plastic containers in the dishwashers here.
Q. I recently heard your podcast on plastic residues in food. My food storage containers are marked with a #5. Are these safe to use and is it OK to put them in the dishwasher?
A. Storage containers made with #5 plastic are free of BPA, a compound that’s been in the spotlight lately. But I think it’s likely that other plastic chemicals, including those found in BPA-free plastic, may eventually be identified as potential concerns as well. Exposing plastics to heat (such as in the microwave or dishwasher) or acids can enhance the leaching of chemicals from containers into foods. Scratched, stained, and warped containers are also less stable. At a minimum, you might want to use glass containers to store acidic foods like tomato sauce and stick to hand-washing your plastic containers. Or, you might want to re-purpose your plastic containers (especially the older ones) for non-food uses, like storing crayons.