Questions 45 to 48 are based on the following passage:
Americans smoke six thousand million cigarettes every year (1970 figures). This isroughly the equivalent of 4,195 cigarettes a year for every person in the country of 18years of age or more. It is estimated that 51% of American men smoke compared with 34%of American women. Since 1939, numerous scientific studies have been conducted todetermine whether smoking is a health hazard. Research teams have conducted studiesthat show beyond all reasonable doubt that tobacco smoking, particularly cigarettesmoking is associated with a shortened life expectancy. Cigarette smoking is believed bymost research workers in this field to be an important factor in the development of cancerof the lungs and cancer of the throat. Male cigarette smokers have a higher death ratefrom heart disease than non-smoking males. (Female smokers are thought to be lessaffected because they do not breathe in the smoke so deeply.) The majority of doctorsand researchers consider these relationships proved their point and say, "Give upsmoking. If you don't smoke--don't start!" Some doctors and research workers--thoughtheir small number is decreased even further--are less sure of the effect of cigarettesmoking on health. They consider the increase in respiratory diseases and various formsof cancer may possibly be explained by other factors in the human environment—atmospheric pollution, increased nervous stress, chemical substance in processed food,or chemical pesticides that are now being used by farmers in large quantities to destroyinsects and small animals. Smokers who develop cancer or lung diseases, they say, mayalso, 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. Apart from the scientific statistics, it might be helpful to look at what smokingtobacco actually does to the human body. Smoke is a mixture of gases, vaporizedchemicals, small particles of ash, and other solids. There is also nicotine, which is apowerful poison, and black tar. As the smoke is breathed in, all these components formdeposits on the membranes of the lungs. One point of concentration is where the air tube,or bronchus, divides. Most lung cancer begins at this point.
Smoking also affects the heart and blood vessels. It is known to be related toBeurger's disease, a narrowing of the small vessels in the hands and feet that can causegreat pain and lead even to the amputation of limbs. While all tobacco smoking affectslife and expectancy and health, cigarette smoking appears to have a much greater effectthan cigar or pipe smoking. However, nicotine consumption is not decreased by the latterforms, and current research shows a causal relationship between all forms of smokingand cancer of the mouth and throat. Filters and low tar tobacco are claimed to makesmoking to some extent safer, but they can only reduce, not eliminate the hazards.