Possible Health Hazards from Different Types of Amorphous Silicas

摘要: A review is given of some of the literature on the effect of different amorphous silicas on the lungs, with emphasis on the type collected in the ferrosilicon industry. Animal experiments indicate that amorphous silica gives a fairly strong initial lung reaction which, however, has little or no tendency to progress, and thus differs significantly from crystalline silica. Most of the reported cases of silicosis among workers exposed to amorphous silica in the ferrosilicon industry have either been transient lung changes or connected to exposure to crystalline silica. Workers exposed only to precipitated amorphous silica do not seem to be at any significant risk. Amorphous silica transforms easily to cristobalite at temperatures much lower than the reported stable temperature range (1470 to 1710°C). It then represents a silicosis hazard if inhaled. Provisional administrative norms (AN) [corresponding to threshold limit values (TLVs)] are suggested.