The semiconductor manufacturing industry is a chemically-intensive, modern industry in which workers are potentially exposed to toxic metals of the IIIA, IVA, and VA families, including gallium (Ga), indium (In), and arsenic (As) (Liao et al., 2006; Chen, 2006). These metals or metalloids are known to have several toxicities and to cause carcinogenesis in animals and humans (Chepesiuk, 1999; Fowler et al., 1993). Symptoms of acute poisoning (including gastrointestinal discomfort, vomiting, coma, and sometimes death) usually occur within 30 min of ingestion of GaAs and InAs, whereas the consequences of chronic poisoning (including anemia, leucopenia, skin cancer, and other internal cancers) are much more insidious (Betoulle et al., 2002). A single dose of 100 mg/kg of GaAs and InAs resulted in acute pulmonary inflammation and pneumocyte hyperplasia after 14 days (Betoulle et al., 2002; Tanaka et al., 1996; Webb et al., 1986). Chronic exposure (2-year observation period) to lower doses (<1 mg/L) of GaAs and InAs produced systemic toxicity and definite pulmonary lesions (Ohyama et al., 1988). In addition, testicular toxicity was observed, and tumor occurrence increased significantly in mice when GaAs and InAs were injected intraperitoneally (Omura et al., 2000). There was also evidence of renal toxicity. CD rats exposed to GaAs developed mitochondrial swelling of renal proximal tubule cells and dose-dependent inhibition of d-aminolevulinic acid dehydratase (ALAD) in the blood, kidney, and liver (Goering et al., 1988; Conner et al., 1995). Arsenic has been classified by International Agency for Research in Cancer (IARC) as a Group I carcinogen, which means that it is a documented human carcinogen. Much of the information linking arsenic to cancer has been obtained through studies of human exposure. Chronic exposure to inorganic arsenic is a potential occupational hazard. The Occupational Safety and Health Administration (OSHA) mandate permissible limits for occupational exposures to ensure the safety and health of workers. The permissible exposure limit (PEL) for arsenic was set at 10 lg/m for an 8-hr day in a 40-hr workweek, and the short-term exposure limit (STEL) measured over a 15-min period was set at 2 lg/m (ATSDR, 2006). Moreover, the biological exposure index (BEI) of total arsenic in urine was set at 35 lg/L (ACGIH, 2004). Taiwan’s history of economic development is well known. The semiconductor manufacturing industry, in particular, has played a decisive role in the development of Taiwan’s economy. Taiwan is the largest producer of CDROMs and light emitting diodes (LEDs) with integrated circuit (IC) products, accounting for 70% and 50% of total worldwide production, respectively. Semiconductor production increased 54% in Taiwan from 1993 to 2000. Currently, about 350 companies in Hsinchu Science-based Industrial Park (HSIP) manufacture ICs, computers and peripheral devices, telecommunication devices, optoelectronics, biotechnology products, and precision machinery. These companies employ over 30,000 people (Chen and Huang, 2004; Chen, 2006). Because workers in the semiconductor manufacturing industry are potentially exposed to a variety of heavy metals, their health may be at risk. In this study, we examined workers’ personal exposure to gallium (Ga), indium (In), and arsenic (As) by monitoring the concentrations of these substances in inhalable-air and H. W. Chen (&) Department of Environmental Engineering and Health, Yuanpei University of Science and Technology, 306 Yuanpei Street, Hsinchu 300, Taiwan, Republic of China e-mail: hwchen@mail.ypu.edu.tw