A model of cigarette smoke particle deposition.

A computer model of aerosol deposition has been extended to cover particle sizes representative of cigarette mainstream and sidestream smoke particles. The model is the first to theoretically predict total airway depositions of mainstream particles in a range which agrees with experimentally determined literature values by including effects of hygroscopicity and normal smoking breathing patterns. The hygroscopic characteristics of cigarette smoke particles are modeled as if they were saturated sodium chloride droplets. A discussion is included showing that this assumption is consistent with presently available data on the hygroscopic characteristics of cigarette smoke. Detailed regional depositions are provided. Though most of the particles are shown to deposit in the periphery, the surface concentrations of deposited particles are not necessarily much greater there than in centrally located airways. A peak in surface concentration at the third generation is exhibited, despite low total depositions there. Central airway surface concentrations are shown to be relatively independent of breathing pattern and airway geometry, implying that the effects of cigarette smoke particle deposition cannot be greatly reduced by changing the pattern of smoke inhalation. For sidestream smoke particles, total percent depositions agree with literature values of 7%-20% for both nonhygroscopic and hygroscopic particles. Deposition is seen to be favored in the periphery of the lung, though surface concentrations of the deposited material can be greater in Weibel Generations 3-6. Peak surface concentrations are again seen to occur in Generation 3. The increased toxicity of sidestream smoke particles may make them as unhealthy as mainstream smoke particles, despite the higher depositions observed for mainstream smoke.