Alveolar macrophages: reduced number in rats after prolonged inhalation of lead sesquioxide.

A decreased number of alveolar macrophages was found in washings from lungs of rats inhaling small particles of lead sesquioxide for 3 to 12 months, as compared with control animals exposed to filtered air. This result contrasts with that reported by others for animals given massive exposures to various dusts for short periods of time. Because the concentrations of lead were comparable to those observed in some industrial(150 microg/m(3)) or urban (10 microg/m(3)) environmental conditions, the results may be significant in terms of human lung clearance processes after such exposures.