When consumers use and buy food plastic packaging bags, they can test them with their senses first. Generally, non-toxic plastic bags are milky white, translucent, or colorless and transparent, which feels smooth and seems to have wax on the surface; Toxic plastic bags are turbid or yellowish in color and sticky to the touch; Plastic bags can be put into water and pressed into the bottom of the water, so that non-toxic plastic bags surface and toxic plastic bags sink.
Professor Wang from the School of Biological and Agricultural Engineering of Jilin University said that plastic packaging bags are divided into food bags and non-food bags. At present, there are several kinds of plastic bags used in the market, such as polyethylene, polypropylene and polyvinyl chloride, among which polyethylene and polypropylene are safe plastics and can be used to hold food. PVC plastic bags are mostly toxic and made of recycled waste plastic bags and dyes. If it is used to package food, it will cause certain harm to human health.
To sum up, generally speaking, even if the food temperature is high, the packaging bags that meet the hygiene standards will not emit toxic substances. But this is only theoretical. In actual use, it is difficult to say whether the packaging bag you see comes from a regular manufacturer or a black workshop. Therefore, it is better to change your eating habits as much as possible.
When a person is not at school, try to eat as often as possible and try to eat in the school cafeteria. Generally speaking, the sanitary conditions of the canteen are higher than those of some snack bars outside.