Theoretical Analysis of Hygroscopic Growth Rate of Mainstream and Sidestream Cigarette Smoke Particles in the Human Respiratory Tract

ABSTRACT

The deposition of cigarette smoke particles (CSP) in the human respiratory tract is difficult to predict theoretically due to the uncertainties in the characterization of these particles. Measured deposition efficiencies for CSP do not agree with those for typical particles of similar size. One explanation of this discrepancy is the hygroscopic growth of CSP once inside the respiratory tract. However, a minimum of experimental data exists and no theoretical study was done to explain the hygroscopic nature of CSP. In this paper, hygroscopic growth of mainstream and sidestream CSP is determined theoretically for conditions simulating the human respiratory tract. Good agreement is found between calculated growth and experimental growth reported in Li [Ph.D. Thesis, Department of Chemistry, Clarkson University, NY, (1993)] and Kousaka et al. [J. Chem. Eng. Jpn. 15: 75–76, (1982)]. Growth ratios ranging from 0 to 1.52 were found for mainstream CSP with initial sizes ranging from 0.03 to 0.6 μm. Growth ratios ranging from 0 to 1.35 were found for sidestream CSP with initial sizes ranging from 0.03 to 0.3 μm. CSP ranging from 0.03 to 0.6 μm reach their equilibrium diameters in less than 0.1 s. Further calculations indicated that CSP do not grow in subsaturated conditions less than 95% which agrees with results reported in Chen et al. [Aerosol Sci. Technol. 12: 364–375 (1990)] and Ishizu et al. [Beitr. zur Tabakforschung 10: 161–168 (1980)]. The hygroscopicity of CSP was found to be significantly less than a salt particle and the resulting growth rates were not large enough to explain the discrepancy between expected and measured deposition efficiencies.