Coagulation of cigarette smoke particles

Experimental measurements on the deposition of cigarette smoke particles (C SP) in the human airways have produced results that are inconsistent with t ypical deposition data based on particle size. Previous work relating to hy groscopic growth indicates that hygroscopicity alone can not account for th is discrepancy. The present study investigates coagulation of CSP modeled a s a polydisperse-charged aerosol as a possible explanation. The results of the model more accurately predict the experimental coagulation data for mai nstream CSP than models that treat CSP as a monodisperse or polydisperse-un charged aerosol. An aerosol with an initial charge distribution based on Bo ltzmann equilibrium yields slightly larger coagulation rates than the mains tream CSP polydisperse-charged model. The numerical results indicate that t he size and charge distribution of sidestream CSP, with a concentration of 10(6) particles cm(-3), remain stable. In 2 s, the size distribution of mai nstream CSP, with a concentration of 10(9) particles cm(-3), shifts to a la rger size while becoming flatter and wider. The diameter of average mass in creases from 0.29 to 0.5 mu m. Numerical results confirm experimental repor ts for mainstream CSP, which indicate that the total number of charged part icles increases with time and, in the early stages of coagulation, the amou nt of charge per particle cannot be estimated based on the particle size. T his study shows that polydisperse-charged CSP, allowed to coagulate for 2 s in the mouth, will not produce size distributions that yield the observed deposition of CSP. However, additional coagulation will take place as the C SP travels through the respiratory tract, which will be investigated in fut ure work. (C) 1999 Elsevier Science Ltd. All rights reserved.