CALCIUM SILICATE

OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.

CAS: 1344-95-2; Chemical Formula: None

OSHA formerly had no specific limit for calcium silicate; the Agency regulated this substance under its generic 8-hour TWA limit for particulates of 15 mg/m³ (total particulate). The ACGIH classifies calcium silicate as a nuisance dust and has an 8-hour limit of 10 mg/m³ for this white powder. The proposed total particulate PEL was 10 mg/m³; however, OSHA has determined that it is appropriate to retain the former 15-mg/m³ total particulate limit for calcium silicate. The 5-mg/m³ limit for the respirable fraction is also retained. Calcium silicate is a white powder.

There are no reported health effects in humans or animals as a result of exposure to calcium silicate. Calcium silicate is thus without long-term adverse health effects if exposures are kept under reasonable control. NIOSH (Ex. 8-47, Table N4) has not conducted an in-depth evaluation of calcium silicate, and no other comments on this substance were received.

OSHA is retaining its 8-hour TWA limits of 15 mg/m³, total particulate, and 5 mg/m³, as the respirable fraction, for calcium silicate. The Agency concludes that these limits protect workers from the significant risk of physical irritation in the workplace.