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committee consists of professionals in a variety of fields, including epidemiology, toxicology, biochemistry, atmospheric science, biostatistics, and pulmonary physiology.

The subject of the committee’s report is the use of epidemiology and related disciplines for the study of possible health effects of exposure to ETS by nonsmokers. Smokers are also exposed to ETS, but the health effects of this exposure, which are likely to be less intense than those of active smoking, are not the subject of this report. The primary goal of the studies reviewed in this report is to determine whether there is a relationship between health outcomes in human populations and ETS-exposure of nonsmokers. It is a formidable task to assess exposure to the complex mixture of ETS with enough precision to permit use in analytic studies, including quantitative risk estimation. For some health outcomes the relevant duration of exposure may be minutes, for others it may be decades. Numerous factors, in addition to exposure to smoke, can influence the risk of illness. These other factors must be taken into account if the magnitude of the effects of exposure to ETS is to be evaluated.


More than 3,800 compounds have been identified in cigarette smoke. The major source, by far, for ETS is sidestream smoke (SS) which is emitted from the burning end of a cigarette in between puffs. The remainder of ETS consists of exhaled mainstream smoke (MS), smoke which escapes from the burning end during puff-drawing, and gases which diffuse during smoking through the cigarette paper. Each of the mixtures, MS, SS, and ETS, is an aerosol consisting of a particulate phase and a vapor phase. However, the smokes of MS, SS, and ETS differ, as the result of changes in the concentrations of individual constituents, the phase (particulate or vapor) in which the constituents are present, and various secondary reactions that chemically and physically alter (“age”) the composition of the smoke. Undiluted SS contains higher concentrations of some toxic compounds than undiluted MS, including ammonia, volatile amines, volatile nitrosamines, nicotine decomposition products, and aromatic amines. However, concentrations of these SS emissions are considerably diluted in the indoor space where ETS exposures take place. The hydrophobic vapor phase

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