Environmental tobacco smoke (ETS) is composed of more than 3,800 compounds. The emitted compounds are found in vapor or particulate phases, or in some cases both. Volatile material may evaporate from particles within seconds to minutes after emission (e.g., nicotine, see Chapter 2). ETS has not yet been adequately characterized such that its chemical and physical nature can be clearly defined. The concentration of any individual or group of ETS constituents in an enclosed space is a function of: (a) the generation rate of the contaminant(s) from the tobacco, (b) the source consumption rate, (c) the ventilation or infiltration rate, (d) the concentration of the contaminant(s) of interest in the ventilation or infiltration air, (e) the degree to which the air is mixed, (f) the removal of the contaminant(s) by surfaces or chemical transformations, and (g) the effectiveness of any air-cleaning devices that may be in use. Exposure to ETS takes place in many settings—such as public, industrial, nonindustrial occupational, and residential buildings—and is a function of the time an individual spends in a microenvironment and the concentration of the ETS constituents in that environment. ETS exposures can be determined either by extrapolation from fixed-location monitoring survey instruments that are portable or by direct personal monitoring, using lightweight pumps and filters worn by subjects.
This chapter will consider the methodology and data available for assessing human exposures to ETS in the physical (external) environment, including the suitability of proposed tracers or proxy air contaminants that would be representative of ETS, available data on ETS exposure from personal monitoring and monitoring of