Use of indium in manufactured materials may be increasing in certain electronic devices such as flat panel displays. Studies in experimental animals and human case reports indicate that indium tin oxide may cause pulmonary disease in humans. The International Agency for Research on Cancer (IARC) has classified indium phosphide as probably carcinogenic to humans (Group 2A) based on a determination of sufficient evidence of carcinogenicity in experimental animals. Limited information is available on the actual users of indium compounds in the U.S. and the potential for occupational exposure among these users. Information on likely downstream users of indium is especially needed in order to conduct more systematic informational surveys of potential indium users, to identify candidate companies for exposure assessment measurements, and to estimate the number of indium-exposed workers. Information on indium use in the U.S. is so limited that basic fact-finding and networking needs to be done to determine if occupational exposure monitoring studies in the U.S. are both warranted and feasible at this time. NIOSH has contacted 47 companies in industry sectors that might use indium compounds. Of the 47 contacted, 33 (70%) have provided some information (by phone) on whether or not they use indium. Twenty two of these 33 companies use indium/indium compounds or process materials that contain indium and have provided some level of information about how indium is used and occasionally information on employee exposures. Five site visits have been conducted so far among the 22 indium-using companies with air sampling performed at two of these companies. Three companies have provided internal air sampling data, and one company provided blood indium information. Two companies indicated having sampled for indium, but need to seek permission to release the data to NIOSH. Two additional companies indicated that they would include indium in their next air sampling survey as a result of the NIOSH contact. NIOSH also visited the National Renewable Energy Laboratory (NREL) in Golden, CO to meet with researchers and EH&S staff regarding use of indium in solar cell production. NREL may also conduct air sampling for indium in the future. Efforts are ongoing to obtain information from additional companies, to arrange site visits, and to conduct air sampling. Processes using indium compounds are usually highly proprietary, hence the extent of information obtained from responding companies varies;however, a picture is emerging of the types of indium compounds used in industry, common indium applications, and jobs with potential or actual indium occupational exposure.

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