Cigarette Smoking as a Cause of Cancer continued	In short, all forms of tobacco use are hazardous, but the hazards are magnified when smoke from the tobacco is inhaled. Furthermore, the nicotine in tobacco is addictive, which makes it extremely difficult for most users to stop the behavior once it has been adopted as part of their lifestyle (DHS, 1988). What's in Cigarette Smoke to Cause so Many Diseases? Tobacco smoke contains literally thousands of chemical agents, including 60 constituents which are known carcinogens, cocarcinogens, or tumor promoters (DHEW, 1879). Because the average smoker consumes about 30 cigarettes daily, the smoker is being subjected to a constant barrage of hazardous agents. After many years of smoking, it is not surprising that smokers die many years prematurely from cancer, heart disease, emphysema, bronchitis, and other chronic and debilitating diseases at rates substantially higher than persons who never smoke. The Health Benefits of Quitting Smoking Quitting smoking greatly reduces the risks for all these diseases (DHHS, 1990). For example, within a year of quitting, a former smoker's risk of heart disease is reduced by nearly 50 percent compared to someone who continues to smoke. Unfortunately, the risks for lung cancer do not decrease as rapidly, but the sooner one quits smoking, the quicker one begins to benefit (Table 3). Usually, after 10 to 15 years off cigarettes, most former smokers' health status is not significantly different from that of a lifelong nonsmoker. Any residual risk following cessation is strongly dependent on total previous exposure to cigarette smoke, length of time off cigarettes, and the health status of the individual at the time of cessation (Shopland, 1990).
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