Recent inhalation toxicology studies suggest that when laboratory rats are exposed to inorganic particles to the point that lung overload occurs, both benign and malignant tumours may develop. The significance of these results for estimating human risk, however, is unclear.; Originally published as a special issue of the journal "Inhalation Toxicology," the contributions to this volume are derived from a symposium held in March, 1995, by the Environmental...