Longitudinal Analysis of the OSHA IMIS Database for Worker Exposure to Crystalline Silica Dust by Industry and Comparisons to the OSHA PEL, ACGIH TLV and NIOSH REL

摘要

Silica is comprised of silicon and oxygen (SiO_2) and is one of the most abundant compounds on earth. It occurs in either a crystalline or non-crystalline (amorphous) form. Crystalline silica, in which the silicon and oxygen atoms are arranged in a tetrahedron structure, exists in several forms, or polymorphs. The most commonly encountered polymorph is quartz; cristobalite, tridymite, tripoli, are other naturally-occurring polymorphs of crystalline silica. The importance of the crystalline feature is that it is highly stable, insoluble in water, and possesses on its surface reactive oxygen species when fractured (Castranova et al., 1996).