Drinking repeatedly boiled water does not cause cancer, some people believe that repeatedly boiled drinking water will increase the content of ammonium nitrite, drinking can lead to nitrite poisoning, which may induce cancer. But the study proved that the water quality that meets the national drinking water requirements even after repeated boiling, the content of nitrite is still very small, the content after 20 consecutive boiling is about 0.038mg/L, the concentration is lower than the national limit of ≤1mg/L standard, can not reach the degree of poisoning, and will not cause cancer. However, because the water is not boiled in time to drink, dust and bacteria may fall in the process of retention, which may cause vomiting, diarrhea and other uncomfortable symptoms after drinking. If there are bacteria into it may also cause gastritis, enteritis and other diseases. Therefore, try to reduce the repeated heating of water as drinking water to prevent the water from being contaminated. Foods that may really cause cancer include unfresh vegetables and fruits, improperly handled overnight leftovers, inadequately pickled pickles, cured meats, moldy cereals and other products, as well as foods such as barbecue, grilled meats and fried products. In the case of long-term consumption in large quantities, it may cause poisoning and there is the possibility of causing cancer, so it is necessary to pay attention to reduce the intake of this type of food in life.