PARTICLE INHALABILITY CURVES FOR HUMANS AND SMALL LABORATORY ANIMALS*

Abstract

Several inhalability curves for nose breathing in humans have been developed. No studies have been designed specifically to develop inhalability functions for animals, although it has been shown that pulmonary deposition of large particles (>4–5 μm) via inhalation is minimal in laboratory animals [Raabe et al., Inhaled Particles VI, pp. 53–63. Pergamon Press, Oxford (1988)]. The logistic function was fitted to these animal deposition data of Raabe et al. (1988) to estimate an inhalability curve for laboratory animals. The logistic function was also fitted to the human data of Breysse and Swift [Aerosol Sci. Technol. 13, 459–464 (1990)] for comparison. The results suggest that ambient concentration is a good predictor (inhalability >95%) of inhaled concentration for humans for particles d_ae. In small laboratory animals, however, the inhalable portion of the ambient concentration is predicted to be 95% for 0.7 μm d_ae particles but declines to 45% for 10 μm d_ae particles. It is, therefore, important to consider the effects of inhalability when estimating dose delivered to the target tissue in animals. In comparing delivered doses between animals and humans, adjusting for inhalability may change not only the magnitude of the difference but also which species is predicted to receive a greater delivered dose.