title: Human subject age and activity level: factors addressed in a biomathematical deposition program for extrapolation modeling.
abstract: A deterministic aerosol deposition model, previously validated by data from adult inhalation exposure experiments, is used to study particle deposition within the developing human lung. Here, two age-dependent lung morphologies are presented, in which the number of tracheobronchial (TB) generations is complete at birth but airway dimensions vary with age; the number of pulmonary (P) generations, however, changes with age, as do the alveolated airway dimensions. Deposition patterns within the two morphologies are compared. For the light and heavy respiratory-activity levels considered, regional TB and P, and total (TB + P) lung deposition fractions are calculated. For all particle sizes (0.2-9.0 microns diameters) tested, total deposition in both morphologies was minimal for the 30-y-old adult and maximal for either of the youngest subjects (7 and 22 mo old). A breakdown of total deposition into lung compartments was specifically addressed for one morphological model. Age-dependent deposition models are intended to aid in future extrapolation efforts to assess the threat to human health from airborne contaminants.
authors.affiliation: Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711.
authors.forename: T B
authors.initials: TB
authors.lastname: Martonen
authors.forename: R C
authors.initials: RC
authors.lastname: Graham
authors.forename: W
authors.initials: W
authors.lastname: Hofmann
mesh_terms: D000328:Adult; D000336:Aerosols; D000375:Aging / Q000502:physiology*; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D008168:Lung / Q000254:growth & development* / Q000502:physiology; D008433:Mathematics; D008954:Models, Biological; D012119:Respiration
chemical_list: D000336:Aerosols