Air dilution physicochemically changes SS and other contributors to ETS. Depending on the degree of air dilution of SS, the concentration of particles in ETS can range from a few micrograms to 300–500 mg/m3. A high degree of air dilution can reduce this yield to a few micrograms per cubic meter. At the same time, the median diameter of the particles will decrease from 0.32 µm to 0.14 or 0.098 µm (Keith and Derrick, 1960; Wynder and Hoffmann, 1967; Ingebrethsen and Sears, 1985). Another change caused by air dilution of SS is the volatilization of nicotine. In ETS, nicotine is present almost exclusively in the vapor phase (Eudy et al., 1985). In addition, redistributions of other constituents in SS due to air dilution might account for the presence of other semivolatile chemicals in the vapor phase of ETS, but we lack data on such effects.
The scientific literature contains an abundance of data on indoor air pollution by ETS (U.S. Public Health Service, 1979; National Research Council, 1981). We limit our review here to measurements made under field conditions and have excluded data from experimental studies. Most of the published data, summarized in Tables 2–4 through 2–9, do not exclude the possibility that, even though the respiratory environments analyzed were polluted largely by ETS, some other sources of pollution contributed to the reported concentrations of individual agents. (Many studies have dealt with the measurement of particulate matter in environments polluted by tobacco smoke. Chapter 5 discusses the measurement of particulate matter, and the results of the studies are summarized in Table 5–1.)
Table 2–4 shows concentrations of carbon monoxide measured in a variety of indoor spaces with and without occupancy by smokers. Carbon monoxide concentrations were generally higher in spaces where smoke was present. They were highly variable, however, and collected data on each space were insufficient (e.g., number of cigarettes smoked and volume of space) to show a consistent relationship.
Tobacco is the only known source of nicotine, so the Nicotiana alkaloid is a specific indicator for tobacco smoke pollution. Nicotine concentrations in smoke-polluted rooms were generally found to be 5–50 µg/m3 and much higher (up to 500 µg/m3) in