Control banding assessment of workers' exposure to indium and its compounds in 13 Japanese indium plants

Abstract: Objectives: This study aimed to assess workers' exposure to indium and its compounds in 55 indium-handling operations among 13 Japanese plants. The surveyed plants were selected from indium-manufacturing plants whose annual indium production exceeded 500 kg. Methods: The Control of Substances Hazardous to Health (COSHH) Essentials control banding toolkit, which contains simple scales for hazard levels, quantities in daily use, and "dustiness" characteristics, was used to assess generic risks of indium-handling operations. The operations were then classified into one of four Control Approaches (CAs). Results: There were 35 indium-handling operations classified into CA4 (requires expert advice) and 16 grouped into CA3 (requires containment). There were three operations classified into CA2 (requires engineering controls) and only one into CA1 (requires good general ventilation (GV) and working practices). Of the 51 operations classified as CA4 and CA3, 36 were found to be improperly equipped with local exhaust ventilation, and the remaining 15 operations solely relied on GV practices. Respiratory protective equipment (RPE) used in the 13 indium plants was examined with reference to the recommendations of the COSHH Essentials and Japan's Technical Guidelines. Conclusions: Our findings suggest that stringent engineering control measures and respiratory protection from indium dust are needed to improve indium-handling operations. Our results show that the most common control approach for Japanese indium-handling operations is to require expert advice, including worker health checks for respiratory diseases and exposure measurement by air sampling.