Dust overloading of the lungs: update and appraisal.

This article reviews recent studies which involve, or impact on, the condition of dust overloading in the lungs of several species, especially the Fischer 344 rat. Its main purpose is to provide an update of the overload concept and new information of possible mechanistic relevance. At present, the most likely general explanation for the suppression of particle transport by the alveolar macrophage (AM) and the development of concurrent events, e.g., increased interstitial dust uptake and prolonged inflammatory response, is the persistent, possibly excessive, elaboration of chemotactic and chemokinetic factors by the AM. The induction of these interrelated events is hypothesized as related to the volume of dust phagocytized by the AM pool. The review concludes, inter alia, that information is badly needed on dust overload in nonrodent species and on the normal role of the AM in dust removal from the human lungs.