Toxic volatile organic compounds in simulated environmental tobacco smoke: emission factors for exposure assessment.

Environmental tobacco smoke (ETS) is suspected to be a major source of exposure to many of the compounds identified as toxic air contaminants. However, we lack emission factors for many of the ETS air toxics for the brands of cigarettes which currently dominate the market and therefore cannot adequately estimate contributions of ETS to such exposures. This study provides up-to-date emission factors for selected air toxics and other volatile organic compounds (VOCs) in simulated ETS and uses them in a mass balance model to evaluate the potential contribution of ETS to air toxics in indoor air and, therefore to indoor exposures to air toxics. Emission factors (microgram/cigarette) were determined for 21 VOCs (including two aldehydes), nicotine and particulate matter in a room-sized (20-m3) environmental chamber with stainless-steel walls, operated under static conditions, using diluted sidestream smoke (no exhaled mainstream smoke) to simulate ETS. Experiments were conducted for Kentucky Reference cigarette 1R4F and for each of six commercial cigarette brands with major market shares. The variabilities in the ETS emission factors among brands of cigarettes were relatively small, ranging from 16 to 31% (expressed as the coefficient of variation) among the six brands. The concentrations of most of the VOCs did not change over the 4-hour periods of the experiments. However, concentrations of 3-ethenylpyridine, phenol, o-cresol and m,p-cresol showed consistent decreases over time, indicating removal by means other than the very low air infiltration rate (0.03 h-1), e.g., deposition onto the chamber surfaces. Emission factors for these compounds were calculated to take these losses into account and the rate constants for these losses were estimated. To estimate indoor concentrations and inhalation exposures to 16 VOCs, nicotine and PM-2.5, the average emission factors for the six commercial brands were used in a time-dependent mass-balance model for two scenarios: a typical office building and an average residence. In general, the indoor concentrations of the air toxics from ETS, under conditions selected to be "typical" rather than extreme, are comparable in magnitude to average outdoor concentrations, indicating that ETS can be a significant contributor to the total indoor concentration and the inhalation exposure for these species. At higher smoking rates, exposures to VOCs from ETS could be several times higher than those modeled under more "typical" conditions.