1. Smoking And Cancer
In the early part of the sixteenth century, explorers returning from the New World brought tobacco to Spain and England. The introduction of tobacco was in response to man's search for contentment; indeed pipe smoking, tobacco chewing, and the use of snuff were reputed to have medicinal action. But, since the earliest times, smoking has also been condemned as a foul-smelling, loathsome custom, harmful to health. The centuries-long controversies became particularly intense after 1930, when the production and use of tobacco, especially of cigarettes, reached enormous proportions and increasing deaths from lung cancer were becoming evident.
Based on evaluations of detailed epidemiologic, clinical, autopsy, and experimental data accumulated over the last 30 years, cigarette smoking has been clearly identified as a causative factor for lung cancer. The risk of developing lung cancer increases directly with increasing cigarette smoke exposure as measured by the number of cigarettes smoked per day, the total lifetime number of cigarettes smoked, the number of years of smoking, the age at initiation of smoking, and the depth of inhalation. Lung cancer death rates for women are lower than for men but have increased dramatically over the last 15 years coincident with the increasing number of women smokers. This increase has occurred in spite of the fact that women smokers use fewer cigarettes per day, more frequently choose cigarettes with filter tips and low tar and nicotine delivery, and tend to inhale less than men. A person who stops smoking has a decreased risk of developing lung cancer compared to the continuing smoker, but the risk remains greater than the nonsmokers for as long as 10 to 15 years after the person stops smoking.
Dr. Alton Ochsner, a nonsmoker and a renowned surgeon who has operated on many patients with lung cancers, has said (1954): "Cigarettes cause cancer ... Indeed in view of research by the American Cancer Society, the National Cancer Institute, the National Institutes of Health, and scores of independent scientists throughout the world, it is appalling that anyone could, doubt the shocking link between smoking and a dozen major health problems."
Lung cancer is not the only cancer to be-associated with smoking. If women are relatively spared by lung cancer, they are not spared by cancer of the larynx. Warren H. Gardner (1966) says that 70% of the women included in his study of laryngectomized women had been smoking until the time of surgery, and that one woman, who had started smoking at age eleven, had been smoking four packs of cigarettes a day for 35 years.
Pipe and cigar smokers experience mortality rates from cancer of the oral cavity, larynx, pharynx, and esophagus approximately equal to those of cigarette smokers. Their risk of developing cancer of the lung is lower than the risk of cigarette smokers, but it is significantly above that of nonsmokers. This is probably due to the fact that pipe, cigar, and cigarette smokers experience similar smoke exposure of the upper respiratory tract, while cigarette smokers (due to their greater tendency to inhale) have a greater exposure of their lungs to smoke than pipe or cigar smokers.
The bronchial epithelium of smokers often shows pre-malignant changes such as squamous metaplasia, atypical squamous metaplasia, and carcinoma. The pathogenesis of these changes is related to the various carcinogenic and co-carcinogenic substances in cigarette smoke; the exact mechanism of these carcinogens remains under investigation.
A recent study found that passive smoking from side-stream smoke increases a person's risk of developing lung cancer. The report states that the probability of nonsmoking wives to develop lung cancer is linked statistically to the smoking habits of their husbands. The relative risk of developing lung cancer was even higher in certain subgroups of nonsmoking women with husbands who smoke—notably those in agricultural settings—further strengthening the evidence that the lung cancers of nonsmoking women were due to their husbands' smoking, not to air pollution.
Home > Lesson 75 - Cancers, Tumors
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