Although many dusts may cause disability in isolated instances and many others may prove to be of considerable significance upon further investigation, the one dust of great and known hazards is silica. The other chemically related dust, asbestos, is known to cause great disability. On the other hand, silica in noncrystalline or gel form, at least in commercial mixtures with aluminum hydroxide, appears to have little if any fibrogenic qualities. Here is an interesting and probably important problem, why do SiO 2 crystalline and SiO 2 gel give such different results in terms of fibrosis of the lungs? Cotton dust is considered to be noxious but variable in its effects and, in general, the case against cotton is not clear-cut. Beryllium grinding, stamping, polishing, and crushing produces a dust which has given even fatal pneumonitis. This hazard is recently recognized, but the industry is not widespread. Methods are available to eliminate dust exposure entirely or to a degree sufficient to avoid serious consequences. Most companies have installed or provided safety equipment. A problem still not solved is to get all workers to use the equipment consistently.