ABSTRACT
Regulations pertaining to Safety and Health Standards for Surface Metal and Nonmetal Mines and for Underground Metal and Nonmetal Mines are specified in Title 30, CFR, Parts 56 and 57, respectively. In these parts of Title 30, exposure limits for airborne contaminants are based on the Threshold Limit Values (TLVs) adopted by the American Conference of Governmental Industrial Hygienists (ACGIH) as set forth and explained in the Threshold Limit Values for Chemical Substances in Workroom Air Adopted by ACGIH for 1973. Exposure limits established in this edition for various mineral silicate dusts containing less than one percent quartz are based on the number of particles per cubic foot of air as determined from impinger samples counted by light-field microscopic techniques. During the past 13 years, the Mine Safety and Health Administration (MSHA) has used these limits to assess the quality of the environments of mineral processing operations.
