Clinically, many lung cancer patients have no symptoms, and often lung cancer is detected when doing routine physical examination, and the early symptoms of lung cancer are similar to other lung diseases, which also delay the treatment of lung cancer. Among the high-risk group, if symptoms of lung cancer are suspected, they should seek medical attention as early as possible and follow medical advice for necessary examinations, such as chest X-ray, sputum to find cancer cells, fiberoptic bronchoscopy, chest CT, percutaneous lung puncture, etc. Sometimes it is not clear at one time, so it should be checked repeatedly until it is clear. 1.Smoking For those who have smoking history, 50-60 years old is the high incidence age of lung cancer. There are many people even suffer from lung cancer due to second-hand smoke. This is because there are at least 2,000 harmful ingredients in the smoke produced by burning cigarettes. With the synergistic effect of a large number of carcinogens and carcinogenic substances in smoke, it damages the normal cells of lung and increases the risk of developing lung cancer. 2. People engaged in heavily polluted industries People engaged in some heavily polluted occupations may be exposed to carcinogens that cause or promote the occurrence and development of lung cancer during their work and labor. Experts say that occupations like casting, rubber production, printing, welding, construction, painting, certain pesticide production and application, petroleum refining, etc. may inhale toxic substances in the process of operation, so people engaged in these occupations have higher lung cancer rate than other occupations. 3.Radioactive gas after decoration A radioactive natural substance called radon has been listed as an important carcinogenic substance in the city by the International Agency for Research on Cancer. This substance exists widely in decoration materials, rocks, building materials, tiles and other decoration materials. Long-term exposure to high level of radon and radon daughters is closely related to the growth of lung cancer and should be given high attention. 4.Air pollution Industrial exhaust gas, if not handled properly, will pollute the environment and atmosphere in factories and mines. In addition, the large amount of coal, diesel and gasoline burned in the city every day as well as the paving of tarred roads and exhaust of motor vehicles can lead to air pollution in dense residential areas. The level of pollutants in the air is directly proportional to the probability of developing lung cancer. Indoors, soot produced by burning coal for heating or cooking food under poor ventilation conditions is also carcinogenic. 5.Balanced diet and nutrition Among the environmental factors that cause cancer, diet and nutrition are important components. Nutritional status can cause cancer through genetic changes, especially vitamins and essential amino acids. The lack of these nutrients can change the genetic material of DNA, which can lead to genetic changes and cancer. 6.Immune deficiency and heredity There are many risk factors for lung cancer, and now the medical profession speculates that lung cancer should be a multifactorial disease. Low immunity, endocrine disorders, depression, and family genetics may lead to the occurrence of lung cancer.