This testimony consists of a letter from NIOSH regarding comments on the Initial Review of the Underground Coal Mine Safety Standard as carried out by the Mine Safety and Health Administration (MSHA). NIOSH believes that to protect workers from hazardous chemicals and physical agents in underground mines, MSHA should continue to use, as a foundation for its health standards the NIOSH criteria documents when appropriate and, in their absence, the Threshold Limit Values of the American Conference of Governmental Industry Hygienists. NIOSH believes that most substances found in the TLV's list can be found in the mining workplace. Thus NIOSH supports retaining the entire list as mining health standards. NIOSH also encourages the review of all NIOSH recommendations made for general industry for their applicability to the mining environment. Statistically based sampling strategies should be considered for sampling air velocity in ventilation systems and for making measurements of explosive gas.