Deposition of Cigarette Smoke Particles in the Human Respiratory Tract

Understanding tobacco related cancer etiology requires the knowledge of cigarette smoke particle (CSP) deposition. Measurements of CSP deposition are inconsistent with typical deposition data. A deposition model that accounts for hygroscopic growth, coagulation, particle charge, and cloud behavior of CSP has not yet been presented. Nor have smoking patterns been accounted for in either deposition measurements or computer models. The dosimetry of Benzo[a]pyrene (BaP), which would add critical information to the relationship between anatomic site preferences of tumors and their histology, is currently unknown. The deposition model presented in this study is the first to accurately account for the dynamic behavior of CSP. Using the model results, the effects of each dynamic behavior on deposition is examined along with the effect of smoking patterns. The dosimetry of BaP is also calculated. The results indicate that coagulation, hygroscopicity, and particle charge increase the total deposition by 16% over the stable charge-neutral case, which predicts 46%. Cloud behavior increases total deposition efficiency by 36% over the simple case. Increasing exhalation time increases the deposition fraction by 3.9%/s. BaP concentrations are found to be as large as 1.8E-4ng/cm2 for the cloud model and 2.4E-5 ng/cm2 for single particle behavior. Mass deposition occurs preferentially in the pulmonary region for all cases. However, significant increases in the tracheo-bronchial region are found if cloud behavior is considered. The model results indicate that cloud behavior,and not particle charge, coagulation, and hygroscopic growth, has a predominant effect on deposition. More data is required on cloud behavior in the airways to improve the accuracy of the model.