Deposition of Crocidolite Asbestos and Glass Microfibers Inhaled by the Beagle Dog

Abstract

The respiratory tract deposition of neutron activated Crocidolite asbestos and glass microfibers was determined in two groups of four Beagle dogs. The dogs were given 60-minute, nose-only inhalation exposures to an aerosol of either asbestos or glass fibers. The radioactivity in tissues and excreta four days after exposure was used to determine the fraction of inhaled fibers deposited in the upper respiratory tract and the deep lung. The activity median aerodynamic diameter (AMAD), count median diameter (CMD) and count median length (CML) were determined from fibers sampled during exposure. Crocidolite asbestos fibers (obtained from the Union Internationale Contre le Cancer) had an AMAD of 1.8 µm, a CMD of 0.25 µm and a CML<5 µm. The fraction of inhaled mass deposited in deep lung was 13–19 percent, while total deposition in the respiratory tract was 54–72 percent. Glass microfibers had an AMAD of 2.5 µm, a CMD of 0.15 µm and a CML of 5.4 µm. Five to 17 percent of the mass of glass fiber was deposited tin the deep lung; total respiratory tract deposition was 45–64 percent. The deposition patterns were similar for these small asbestos and glass fibers inhaled by dogs and in good agreement with previous predictions made for man.