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: 1317-65-3; Chemical Formula: None
OSHA formerly had no specific limit for marble dust, but regulated this substance under the generic total particulate limit of 15 mg/m3. The ACGIH has established an 8-hour TLV-TWA of 10 mg/m3 for marble dust containing less than 1 percent quartz (measured as total dust). Marble dust, a metamorphic form of calcium carbonate dust, is an odorless and tasteless powder or crystal. OSHA proposed an 8-hour TWA limit of 10 mg/m 3 for marble dust as total particulate containing less than 1 percent quartz and 5 mg/m3 TWA for the respirable fraction of this dust. NIOSH (Ex. 8-47, Table N4) did not specifically evaluate the effects of marble dust exposure, and no one else commented on marble.
In the final rule, OSHA is retaining its former total particulate limit for marble of 15 mg/m3, as well as the respirable particulate limit of 5 mg/m3. OSHA finds that these limits protect exposed workers against the significant risk posed by physical-irritant properties of marble.