Because the main components of industrial salt and edible salt are sodium chloride, there is no big difference in taste, and the amount of salt used as a seasoning in cooking is limited, so the harm of industrial salt to human body is mostly a chronic process. For example, industrial salt may contain impurities such as lead, arsenic, mercury, cadmium and nitrite, and long-term accumulation of heavy metals may cause dizziness, dermatosis, myocardial injury, neuritis, multiple organ dysfunction and muscle spasm. When a large amount of nitrite enters the human body, the low-iron hemoglobin carrying oxygen in the body can be turned into methemoglobin. As soon as methemoglobin meets oxygen, it is firmly combined and difficult to separate. In this way, the whole body tissue of the human body will be deprived of oxygen. When the human body ingests 0.3 ~ 0.5 grams of nitrite, it can cause acute poisoning and 3 grams can kill people. Once the human body is poisoned, it will come on in ten minutes, and symptoms such as dizziness, head swelling, tinnitus, general weakness, numbness in hands and feet, nausea and vomiting, diarrhea, dyspnea, etc. will occur, and in severe cases, convulsions and coma will occur. Of course, the consumption of industrial salt alone is less than the amount of acute nitrite poisoning.