Plastics used in disposable packaging for food may leach chemicals that are bad for kids.  Reusable plastic containers ("Tupperware" etc.) may also leach chemicals.  More chemicals are found in foods that are heated in these containers; even the heated dishwasher seems to increase chemical leaching.  It might be better to transfer these foods to ceramic plates or glass dishes before reheating them.

This article from the New York Times gives more details:

https://www.nytimes.com/article/plastics-to-avoid.html

The Gist

• There’s significant evidence that exposures to two types of chemicals found in plastics — phthalates and bisphenols — can affect health, especially if the exposure occurs in the womb or during early childhood.
• Existing government regulations are inadequate to protect us from these chemicals, many researchers say, but simple strategies — like eating more whole foods and fewer packaged or processed foods, using metal or glass containers, and avoiding plastics in the dishwasher or microwave — can reduce your exposure.
• To decrease phthalates in your home, use a HEPA-filtered vacuum and avoid vinyl products like shower curtains.
• For toys that go in your baby’s mouth, it’s safest to choose those made of wood or silicone.
• Use personal care products that are fragrance- or phthalate-free. (Products labeled as “unscented” may still contain fragrance and aren’t necessarily free of phthalates.)

     --  Dr. Epstein