来源：考试大 2010-07-14 10:15
Smoking and Cancer （吸烟和癌）
1. Americans smoke six thousand million cigarettes every year (1970 figures). This is roughly the equivalent of 4,195 cigarettes a year for every person in the country of 18 years of age or more. It is estimated that 51% of American men smoke compared with 34% of American women.
2. Since 1939, numerous scientific studies have been conducted to determine whether smoking is a health hazard. The trend of the evidence has been consistent and indicates that there is a serious health risk. Research teams have conducted studies that show beyond all reasonable doubt that tobacco smoking, particularly cigarette smoking, is associated with shortened life expectancy.
3. Cigarette smoking is believed by most research workers in this field to be an important factor in the development of cancer of the lungs and cancer of the throat and is believed to be related to cancer of the bladder and the oral cavity. Male cigarette Smokers have a higher death rate from heart disease than non-smoking males. (Female smokers are thought to be less affected because they do not breathe in the smoke so deeply.) The majority of doctors and researchers consider these relationships proved to their satisfaction and say, "Give up smoking. If you don't smoke—don't start!"
4. Some competent physicians and research workers—though their small number is decreased even further—are less sure of the effect of cigarette smoking on health. They consider the increase in respiratory diseases and various forms of cancer may possibly be explained by other factors in the complex human environment — atmospheric pollution, increased nervous stress, chemical substances in processed food, or chemical pesticides that are now being used by farmers in vast quantities to destroy insects and small animals. Smokers who develop cancer or lung diseases, they say, may also, by coincidence, live in industrial areas, or eat more canned food. Gradually, however, research is isolating all other possible factors and proving them to be statistically irrelevant.