Abstract
Two single-exposure inhalation studies on rats were carried out for purposes of following the excretion and tissue distribution patterns of niobium with time, using niobium-95 as a radioactive tracer. For the first exposure the aerosol was generated from an oxalic acid solution containing only the tracer; for the second, the solution contained an additional quantity of stable niobium-93. Twice as much of the carrier aerosol was initially deposited in the whole animal, but only one-half as much of this larger particulate material was initially associated with the lower respiratory tract. One repeated exposure experiment was carried out, and the pattern of buildup and loss of niobium-95 from the whole body indicated that the hazard from chronic inhalation of this material could be assessed from calculations based on data derived from a single exposure.
