The harm of waste oil?

There are three kinds of gutter oil: one is gutter oil in a narrow sense, that is, oily floating objects in sewers or leftovers from hotels and restaurants (commonly known as swill) are simply processed and refined; The second is the oil produced by the processing and refining of inferior pork, pig offal and pig skin; Third, the oil used for fried food should be reused after a certain number of times, or some new oil should be added. There are three main flows of waste oil: chemical plants (producing chemical products); Restaurant → collector → restaurant, restaurant (low price purchase) → customer table; Farms (feed for livestock). In the process of refining "gutter oil", a series of chemical changes, such as rancidity, oxidation and decomposition, occur after animal and vegetable oils are polluted, resulting in substances that are highly toxic to human body; Arsenic is one of them. Once people use "waste oil" containing a lot of arsenic, it will cause symptoms such as indigestion, headache, dizziness, insomnia, fatigue and discomfort in the liver area. Gutter oil contains aflatoxin and benzopyrene, both of which are carcinogens, which can cause gastric cancer, intestinal cancer, renal cancer and cancers of breast, ovary and small intestine.