Pulmonary Reaction to Metallic Aluminum Powders

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Abstract
Fine metallic aluminum powders inhaled by hamsters and guinea pigs caused no pulmonary fibrosis. In rats that inhaled these dusts, scattered small scars resulted from foci of lipid pneumonitis. Alveolar proteinosis, more pronounced in rats, developed in all three species that inhaled aluminum dusts. It resolved spontaneously, however, and the accumulated dust deposits cleared rapidly from the lungs after cessation of the exposure. No evidence of alveolar proteinosis has been found in humans exposed to aluminum dust, in contrast, the intratracheal injection of large doses (100 mg) of aluminum powders into rats caused focal pulmonary fibrosis. However, with smaller doses, the lesions were not only correspondingly smaller, but they remained noncollagenous and cellular. Mo fibrosis occurred in the lungs of hamsters injected intratracheally with the same powders. These experimental results indicate that very fine metallic aluminum powders are nonfibrogenic when inhaled, and that focal pulmonary fibrosis in rats, after intratracheal injection of these powders, is not only dependent on the artifact of intratracheal injection, hut also upon attainment of a critical, very high dose (100 mg).