Ann. occup. Hyg., Vol. 47, No. 2, pp. 157-164, 2003
© 2003 British Occupational Hygiene Society
Published by Oxford University Press
Partitioning Theory for Respiratory Deposition of Semivolatile Aerosols
Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, CB 7431 Rosenau Hall, Chapel Hill, NC, 27599-7431, USA
Received 18 July 2002; in final form 7 November 2002
The objective of this work is to model the deposition of semivolatile aerosols in the lungs based on gasparticle and tissueair partitioning theory. Semivolatile compounds exist in air as both particles and gases simultaneously. Mass distributes between the two phases according to a gasparticle partitioning ratio, Rpg = Kp(TSP). Particle deposition in the lungs is a function of aerodynamic diameter, whereas gas deposition is a function of tissue solubility, which is related to the airlung partitioning ratio, Kla. Therefore, deposition to the lungs will vary with Rpg and Kla. These and other parameters determine a dimensionless deposition number, D, which indicates whether particles or gases are most responsible for deposition of semivolatile chemicals in the lung. The deposition number allows industrial hygienists to design effective air sampling strategies and control measures that will minimize risks associated with exposure to semivolatiles. Examples of deposition numbers for common semivolatile pollutants are provided, including alkanes, polycyclic aromatic hydrocarbons, pesticides and polychlorinated biphenyls.
Keywords: semivolatiles; exposure; deposition; lung; partitioning; Kp, Rpg; dose; metalworking fluid