Blumberg suggests it's best to just stick to heating your food in anything but plastic. Now, quick aside, BPA-free plastic containers aren't the answer because research suggests that BPS and BPF ...

Look for plastic products with a “BPA-free” label, and be aware that plastics ... To identify it, look for the number 5 recycling symbol.

The number is inside the triangular recycling mark. 1, 2, 4 or 5 means the plastic is BPA free. They quite often say BPA free on them. A 3 or a 7 means that the plastic may contain BPA.

bisphenol A (BPA), di(2-ethylhexyl) phthalate (DEHP) and polybrominated diphenyl ethers (PBDEs). BPA and DEHP are found in plastic food packaging and PBDEs… ...