SIZE CHARACTERISTICS AND AGING OF THE ENVIRONMENTAL TOBACCO-SMOKE

The work presented here is a study of the behaviour of the particulate phase of ETS under controlled laboratory conditions and in real indoo r environments with the aim of providing information for assessment of human exposure to ETS. This paper reports investigations of the size distribution of ETS and changes to the distribution with time under a range of environmental conditions. Measurements were performed using t wo instruments, the Scanning Mobility Particle Sizer and the Aerodynam ic Particle Sizer, which enabled the determination of the precise loca tions of ETS peaks at frequent short time intervals. While total parti cle concentrations or changes in concentrations are not specific marke rs of ETS, peaks related to ETS in the spectral distribution of atmosp heric particles, for a properly designed experiment, are. The presence and locations of these peaks are characteristic of ETS in indoor envi ronments and are clearly distinguishable from the background particle distribution. It is demonstrated that an initial ETS size distribution in an indoor environment about 10 min after generation by a human smo ker has a major peak in the submicron range between 60 and 90 nm. The location of the peak does not depend on the relative humidity, but doe s depend on the way the cigarette is smoked. An increase in particle s ize in the range of 20 to 50%, takes place in the first 30 to 60 min a fter ETS generation and then remains unchanged for the duration of the experiment. A decrease in particle size (shrinkage), was not observed during these experiments. Particle shrinkage has been reported in the literature. Both the SS and the MS smoke reveal bimodal size distribu tion. In both cases the most significant, in terms of particle numbers , is the submicron peak. Natural ventilation, which is the most common type of ventilation for residences, is often not sufficient for effec tively reducing human exposure to ETS. Controlled chamber experiments are useful for investigations of general trends in ETS size distributi on and concentration and the results from such experiments, in most ca ses, correlate well with those from real indoor measurements. There ar e however, aspects which show certain differences between the two type s of experiments. These differences indicate that chamber experiments can not fully simulate indoor measurements, and results from such expe riments should be treated with caution when applied to exposure assess ment. (C) 1997 Elsevier Science B.V.