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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects
FIGURE 11–1 Known and suspected mechanisms for effects of tobacco smoke on airways. Solid lines=known mechanisms; dashed lines=suspected mechanisms.
Health Service, 1984). In the large airways there is hypertrophy and hyperplasia of the mucous glands. These changes are followed by an increase in mucus production that leads to increased cough and sputum production. Structural changes in smaller airways range from relatively mild inflammation to narrowing and closure of airways due to inflammation, goblet cell hyperplasia, and intraluminal mucus. Changes in the parenchyma include increased numbers of inflammatory cells and ultimately destruction of the alveolar walls, most commonly in the central part of the lobule, i.e., the development of centrilobular emphysema (see Figure 11–1).
The link between airway disease and parenchymal disease is poorly understood. Smokers with severe functional impairment usually have an appreciable amount of emphysema (U.S. Public Health Service, 1984).
Cessation of smoking leads to a rapid decrease in respiratory symptoms, an improvement in lung function, and a shift towards the nonsmoker’s rate of decline of FEV1 (U.S. Public Health Service, 1979, 1984). These improvements are usually seen regardless of the functional level at which cessation occurs.
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