because the subjects can see another person actively smoking in their vicinity. Chapter 10 reviews experimental studies that evaluate these acute comfort aspects under controlled conditions.

Chapters 11 and 12 assess and evaluate possible nonneoplastic and neoplastic pulmonary effects of exposure to ETS by nonsmokers. Over the past 15 years, a number of studies in children and in adults have assessed various possible acute and chronic pulmonary effects subsequent to long-term exposure to ETS. Individuals who have chronic lung diseases, such as patients with asthma, alpha-l-antitrypsin deficiency, or cystic fibrosis, are potentially hypersensitive to the effects of ETS exposures.

Chapter 13 reviews and evaluates reports of cancers other than lung that may be associated with exposure to ETS in nonsmokers.

Chapter 14 discusses the possible association of exposure to ETS with chronic and acute cardiovascular responses and cardiovascular diseases in nonsmokers. Individuals with chronic disease that compromise the cardiovascular system, such as patients with a history of angina pectoris, are at a high risk for developing abnormal cardiovascular responses following exposure.

Chapter 15 considers evidence that a number of other health effects are linked to ETS exposure in children of smokers, including lower relative growth, frequency of ear infections, and low birthweight (with nonsmoking pregnant mothers).

The studies reviewed here are epidemiologic and experimental. Epidemiologic studies include case-control studies, in which subjects are selected according to whether or not they have the health outcome being studied, and cohort (or prospective) studies, in which subjects are classified according to whether or not they have been exposed to ETS. Cross-sectional studies are those in which an assessment is made of a population at one point in time. Longitudinal studies follow a group of persons over time. In experimental studies, subjects are exposed to ETS under controlled conditions often using chamber studies. Most studies of ETS have been cross-sectional rather than longitudinal. To be informative, a study must evaluate a sufficient number of people to provide a precise estimate of the effect; obtain valid information regarding the history of exposure and health status of the individuals; and, of course, the statistical analyses must be appropriate to the study design. The appropriate design and use of these epidemiologic methods for the study of air pollution and possible health effects

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