Previous chapters have dealt with the formation and composition of tobacco sidestream smoke, its contribution to environmental tobacco smoke (ETS), and the conditions that govern the physicochemistry and toxicity of ETS. Personal monitoring of exposure and analysis of the respiratory environment enable us to estimate the level of toxic agents for individuals exposed to ETS. Studies on the uptake of smoke constituents by individuals and on the metabolic fate of such constituents can provide information relative to epidemiologic observations and the actual exposure levels of different populations.
Exposure to ETS may depend on several factors, including the number of smokers in an enclosed area, the size and nature of the area, and the degree of ventilation. Thus, optimal assessment of exposure should be done by analysis of the physiological fluids of exposed persons rather than by analysis of respiratory environment. The development of new biochemical methods enables us to obtain measurements of exposure to ETS by determining the uptake of specific agents in body fluids and calculating the risk relative to that of the exposure of active smokers. The uptake of individual agents from ETS can be determined by biochemical measures that have been developed for assessment of active smoking behavior, as long as these measures are sensitive and specific enough for quantitating exposure to such agents by nonsmokers.