ACGIH recommends TLVs for three groups of chromium compounds: Chromium metal and trivalent chromium (Cr III) compounds, TLV-TWA of 0.5 mg/m3, as Cr, to minimize the potential for respiratory tract and dermal irritation, and dermatitis. In the absence of substantive carcinogenicity data from animal or epidemiological studies, an A4, Not Classifiable as a Human Carcinogen, notation is designated. Water-soluble hexavalent chromium (Cr VI) compounds, TLV-TWA, 0.05 mg/m3, as Cr, to minimize the potential for respiratory tract irritation and cancer, dermatitis, and possible kidney damage. From the available evidence and the IARC inclusion of soluble Cr VI compounds as carcinogenic to humans, an Al, Confirmed Human Carcinogen, notation is designated. Water-soluble Cr VI compounds are those for which Biological Exposure Indices (BEIs) have been recommended (see BEI Documentation for Chromium VI, Water-soluble Fume). TLV-TWA of 0.05 mg/m3, as Cr, and the Al notation are also recommended for Chromite ore processing. Insoluble chromium VI (Cr VI) compounds, TLV-TWA, 0.01 mg/m3, as Cr, to minimize the potential for respiratory tract irritation and cancer, and dermal irritation. Experimental animal studies and lung cancer data from workers exposed to insoluble Cr VI compounds provide the basis for an Al, Confirmed Human Carcinogen, notation. Additional dose-response data are needed to modify the TLV-TWA of 0.01 mg/m3, as Cr, for insoluble Cr VI compounds. Sufficient data were not available to recommend Skin or SEN notations or a TLV-STEL.