Hygroscopic growth and deposition of inhaled secondary cigarette smoke in human nasal pathways

To ascertain the threat to human health posed by the inhalation of the part iculate phase for secondary cigarette smoke (SCS), it is necessary to deter mine the doses delivered to airway cells. The risk assessment of SCS partic les is complicated by their hygroscopic properties. Inhaled particles that are hygroscopic may absorb the water vapor that is present in a warm, humid environment such as that found in the human respiratory system. As a direc t result, the physicochemical characteristics of a particle such as size, s hape, density, and composition may experience significant changes. Herein, the effects of hygroscopicity and deposition of SCS particles are examined in the nasopharyngeal region of the respiratory tract through which particl es travel before entering the lung. To accomplish this goal, a computer mod el is defined to describe the anatomical features of the airways within the human head and throat, Then the effects of water vapor uptake and depositi on on inhaled particle size distributions are formulated. The results of th e simulations indicate that hygroscopicity is a critical factor affecting t he dynamics of inhaled SCS.