1.Diet The tumors directly related to diet in China include stomach cancer, esophageal cancer, liver cancer, intestinal cancer and breast cancer, and the mortality rate of the above cancers accounts for about 45% of all malignant tumors. Meat contains a lot of fat and heat, people who consume more meat are prone to colon cancer, and nitrite of food can cause gastrointestinal tumors such as esophageal cancer, stomach cancer and liver cancer. Obesity is also related to many cancers. 2.Smoking Among various cancer-causing factors, smoking and passive smoking are the most important factors leading to tumor death. Cigarette smoke contains more than twenty kinds of chemicals that can cause tumors, which can lead to oral cancer, laryngeal cancer, esophageal cancer, stomach cancer, pancreatic cancer, kidney cancer and bladder cancer, in addition to lung cancer. 3.Rays Ultraviolet rays in sunlight are a kind of low-energy rays, and people who are often exposed to strong sunlight are prone to skin cancer. Rays from X-rays or radioactive isotopes have higher energy and can penetrate clothes and skin, leading to cancer of body tissues. 4.Viruses Some viruses can also cause tumors. Such as human papilloma virus (HPV), EBV, etc. 5.Occupational diseases Poor working and living environment, such as mine workers, long-term exposure to dust. 6.Environmental pollution Air pollution, water and soil pollution are harmful to human body. 7.Mental factors Many clinical data show that emotional well-being has a significant relationship with the occurrence of cancer. Most cancer patients have major trauma or have long time mental depression and depression, etc. People with cheerful personality rarely suffer from cancer. 1.Lag time The chemical substances and radiation that can cause tumor are called “carcinogens”. Carcinogens go through many steps to trigger a series of genetic changes (“mutations”) and finally stimulate cell proliferation, which takes a long time and may take decades for tumors to occur. For example, lung cancer occurs in young people 20 to 30 years after they start smoking, a period of time known as the lag time.