You can't. Plastic lunch boxes heated by microwave ovens will release toxic substances. Every plastic has a thermal limit. Among the food materials, polypropylene (PP) can tolerate 140℃, followed by polyethylene (PE), which is 1 10℃, while polystyrene (PS) can only tolerate 90℃. If the temperature exceeds their heat resistance limit, plasticizers may be released, so avoid using high-temperature hot plastic lunch boxes to heat food for a long time.

Plasticizers will interfere with the endocrine system of human body and have an impact on the reproductive system of human body, especially men. Animal experiments show that long-term intake of plasticizer may damage the growth of liver, kidney and shadow. Plastic products also have shelf life. After expiration, the plastic will age, change color and become brittle. If used plastics are found to be yellow or no longer transparent, they should be replaced as soon as possible.