Extrapolation from rat studies with environmental tobacco smoke (ETS) to humans: comparison of particle mass deposition and of clearance behavior of ETS compounds.
The relative deposition of inhaled heterodisperse particles of the size of environmental tobacco smoke (ETS, mass median aerodynamic diameter 0.2 micron, geometric standard deviation 1.5) is about the same in the tracheobronchial tree and is lower in the pulmonary region of the rat than in the same regions of humans. However, model calculations show that per cm2 of surface area the deposition rate of ETS particle mass shows a doubling in rats as compared to humans in the transitional zone of the lung, i.e., airway generations 16-20. Within the human airways, mainstream smoke particles are deposited to a higher degree in generations 2-5 than in the transitional zone, whereas the opposite applies to ETS particles. Significantly higher pulmonary retention in man than in rats of inhaled ETS particles and their constituents (e.g. cadmium) leads to additional differences in the dose accumulating in the lung over time. Such differences in deposition and retention characteristics of inhaled ETS have to be considered when extrapolating results from rat studies to humans.
D000336:Aerosols; D000818:Animals; D002104:Cadmium / Q000378:metabolism; D006801:Humans; D008657:Metabolic Clearance Rate; D051381:Rats; D012137:Respiratory System / Q000378:metabolism*; D013045:Species Specificity; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
D000336:Aerosols; D014028:Tobacco Smoke Pollution; D002104:Cadmium