The Threshold Limit Values for Chemical Substances (TLV-CS) Committee was established in 1941. This group was charged with investigating, recommending, and annually reviewing exposure limits for chemical substances. It became a standing committee in 1944. Two years later, the organization adopted its first list of 148 exposure limits, then referred to as Maximum Allowable Concentrations. The term "Threshold Limit Values (TLV)" was introduced in 1956. The first list of Threshold Limit Values and Biological Exposure Indices (the "TLVs and BEIs" book) was published in 1962"." A new edition is now published annually. Today's list of TLVs and BEIs includes over 600 chemical substances and physical agents, as well as over 30 Biological Exposure Indices for selected chemicals.