肺癌的发病原因,至今还不完全清楚。根据目前所知,肺癌的病因中,有人体和周围环境两个方面的因素,其中环境因素已愈来愈引起人们的重视。 1.吸烟:近二十多年来,吸烟同肺癌的关系,受到了极大的重视,认为吸烟是肺癌的一个重要致病因子。有人曾对一百万以上的人群进行了两年以上、七次对照观察研究(其中美国作了五次, The causes of lung cancer, is still not fully understood. According to the current knowledge, the cause of lung cancer, there are two factors of the human body and the surrounding environment, of which environmental factors have drawn more and more attention. 1. Smoking: In the past twenty years, the relationship between smoking and lung cancer has drawn great attention. It is considered that smoking is an important risk factor for lung cancer. Someone once conducted more than two years and seven controlled studies on more than a million people (including five in the United States,