RESUMEN
Short-and long-term animal experiments are used to examine the toxicology and biopersistence of various types of fibers. In order to ensure an adequate exposure dose for testing, modern experimental protocols specify that the exposure aerosol (in an inhalation test) or the fibers (in an intratracheal instillation [IT] test) must contain at least a minimum concentration of long (> 20 mum) rodent-respirable fibers. As produced and handled, most fibers contain a distribution of diameters and lengths, only some of which are both long and rodent-respirable. Therefore, it is necessary to size-separate the fibers to enrich the proportion of long, rodent-respirable fibers in the material to be tested. This article presents a new and relatively simple method for size separation that avoids some of the difficulties associated with other methods. The method, termed horizontal diffusion elutriation (HDE), is illustrated by size-separating refractory ceramic fiber (RCF) and four polycrystalline alumina (PCA) fibers.