According to the different uses of the material, there are generally professional marks on the plastic lunch boxes to distinguish them.1-PET polyethylene terephthalate: Carcinogens produced after ten months of use. Plastics of this material have a high probability of being discarded after use, and are usually used as mineral water bottles, milk bottles, etc. It is not suitable for supercooled and superheated water, which is easy to precipitate carcinogen DEHP.2-HDPE (High Density Polyethylene):