What are the causes of lung cancer

The cause of lung cancer is very complex and has not yet been fully elucidated. It is generally believed to be related to the following factors.

(I) Smoking It is generally acknowledged that smoking is the most important risk factor for lung cancer. Tobacco contains more than ten chemical carcinogens, among which the aromatic hydrocarbon "benzopyrene" is an important carcinogen. At the same time, cigarettes also contain carcinogenic nitrosamines and carcinogens such as catechol. Some studies have shown that smokers die 14 times more from lung cancer than non-smokers.

(B) Physical and chemical carcinogens Long-term exposure to industrial carcinogens has been confirmed as occupational factors that cause lung cancer in humans, including asbestos, inorganic arsenic, chromium, nickel, coal tar, dichloromethyl ether, mustard gas, asphalt fume, chloromethyl ether, radon and radon progeny, etc.

(III) Air pollution Air pollution includes indoor micro-environment pollution and outdoor macro-environment pollution. For example, passive smoking, fuel combustion and carcinogens may be produced during cooking. Data show that using coal indoors and being exposed to coal smoke or its incomplete combustion products are risk factors for lung cancer, especially for female prostate cancer. The oil smoke released during cooking is also a carcinogenic factor and cannot be ignored.

Car exhaust, industrial waste gas, and road asphalt in cities all contain carcinogens, the main of which is benzopyrene. According to statistics, the incidence of lung cancer in cities is significantly higher than in rural areas, and the incidence in large cities is higher than that in medium and small cities. A 12-year prospective survey and analysis of a rubber factory in Shanghai showed that although antioxidants in the rubber industry are a cause of the increase in lung cancer among rubber workers, they are not as harmful as smoking. Smoking and occupational exposure to rubber have a significant additive effect. The incidence of lung cancer in Yunnan tin mines is particularly high, with an incidence of lung cancer among underground workers of 435.44/100,000. After balancing the smoking factor, smoking is still the main factor causing lung cancer in miners. Therefore, urban air pollution should include factors such as smoking and occupational exposure.

(IV) Ionizing radiation Large doses of ionizing radiation can cause lung cancer. In addition to the fact that the radiation produced by radon and oxygen progeny increases the risk of lung cancer in miners, some people in the UK have reported that the incidence of lung cancer has increased significantly among patients with ankylosing osteomyelitis who received radiation therapy and survivors of the Japanese atomic bomb.

(V) Diet and Nutrition In recent years, there have been many reports on the increased risk of lung cancer in people who consume less vitamin A in their food or have low serum vitamin A levels. Animal experiments have shown that vitamin A and its derivative beta-carotene can inhibit tumors induced by chemical carcinogens. The results of prospective population observations conducted in New York and Chicago, USA, also show that the intake of natural vitamin A and beta-carotene in food is negatively correlated with the occurrence of cancer a few years later, the most prominent of which is lung cancer. Although people with vitamin A deficiency should be corrected to reduce the risk of lung cancer, vitamin A is not enough to change the prognosis of existing early lesions in high-risk groups.

(VI) Others The American Cancer Society lists tuberculosis as one of the risk factors for lung cancer. For men with a history of tuberculosis, especially those with tuberculosis scars, the risk of lung cancer is 5 times that of the normal population, and for women, the risk is 10 times that of the normal population. The main histological type of lung cancer in patients with a history of tuberculosis is adenocarcinoma.