Coagulation and Deposition of Cigarette Smoke Particles in the Human Lung

BAHMAN ASGHARIAN (1), OwenT. Price (1), Colin Dickens (2), John McAughey (2)

(1) Applied Research Associates, Raleigh, NC. (2) British American Tobacco, Southampton, United Kingdom.

     Abstract Number: 835
     Last modified: August 6, 2010

Abstract
Estimates of internal dose of inhaled cigarette smoke particles (CSP) in the human lungs are required in heath risk assessment studies. Deposition of CSP is drastically different from that of environmental particles because of loss mechanisms unique to CSP. Due to its high number concentration, freshly generated CSP coagulate rapidly resulting in particle growth and reduction in airborne number concentration. In addition, the breathing pattern differs between environmental aerosol exposures and cigarette puffs. A physiologically-based, mathematical model was developed for the deposition of CSP in human lung airways during a breathing cycle that consisted of inhalation of a cigarette puff with dilution air, pause, and exhalation of the puff. Mixing of the puff with dilution air during inhalation produced a time-varying inlet concentration of the inhaled puff. The deposition model was based on the general dynamic transport equation with separate terms for losses and coagulation. Airway concentration of CSP was determined from the solution of the transport equation and used to find airway loss fractions. The growth and concentration of CSP were found to be directly related to the initial concentration of the puff before mixing with the dilution air. A significant coagulation was observed at initial puff concentrations of near and above 1011 #/cm3. At this concentration, CSP were found to reach their final size in about 10 seconds; after which there was little or no further growth in size nor change in concentration by coagulation. Particle coagulation was found to be insignificant for initial concentrations of CSP below 108 #/cm3. The predicted deposition model of inhaled CSP can be combined with observation of tissue response toward the development a comprehensive risk assessment model for the inhalation of CSP. This study was funded by British American Tobacco.