Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, HETA 2009-0214-3153, 2012 Mar; :1-97
On August 12, 2009, the National Institute for Occupational Safety and Health (NIOSH) received a management request for a health hazard evaluation (HHE) at an indium-tin oxide (ITO) production facility in Rhode Island. The company submitted the request because of the potential lung toxicity of indium compounds. The request was for an evaluation of the preventive measures put in place by the company. To conduct the evaluation, NIOSH staff reviewed and analyzed industrial hygiene and health data provided by the company and healthcare providers, and reviewed supporting documents provided by the company. From April 7 through 9, 2010, we visited the facility to conduct interviews with managers and workers, tour the facility, collect bulk samples, and conduct limited air sampling. We also visited the current pulmonary function laboratory and met with members of the current healthcare provider team at a local hospital. For historical industrial hygiene data, we grouped samples by type and work area, calculated average values, and examined trends over time. We compared average values to the NIOSH recommended exposure limit (REL) of 0.1 milligrams per cubic meter (mg/m3). Notably, NIOSH recommended this exposure limit before indium lung disease was discovered. There is no exposure limit set by regulation. For historical health data, we evaluated test quality, classified results using updated reference equations, calculated frequencies of abnormalities, and examined trends over time. We examined associations between abnormalities and worker characteristics such as employment status, hire date, job title category, blood indium concentration, and estimated indium exposure from the industrial hygiene data. We found that, since acquiring the facility in 2002, the company made extensive workplace changes. These changes included ventilation enhancements, isolation of processes, introduction of enclosures on machines, a comprehensive respiratory protection program, and a comprehensive medical surveillance program. Records from 13 air sampling surveys that were conducted between 2004 and mid-2010 were provided to NIOSH. We did not find a clear trend in indium concentrations over time. Indium air levels exceeded 0.1 mg/m3 throughout the facility and were highest in the refinery and reclaim areas. Records from 57 workers who participated in the medical surveillance program from 2002 to mid-2010 were provided to NIOSH. We found that some current and former workers had abnormalities on medical tests suggesting work-related health effects. For instance, more than half of those tested had blood indium concentration greater than 5 micrograms per liter (mcg/L) after hire. This is important because in Japan, doctors have found indium-related lung effects at 3 mcg/L and greater. Restriction on spirometry after hire and excessive decline during employment in forced expiratory volume in 1 second (FEV1) (a lung function measurement made using spirometry) were more common than expected. These findings are important because restriction on spirometry can be a sign of lung disease and excessive decline in FEV1 can be an early marker of lung disease; both have been documented in workers who developed severe lung disease while working with indium compounds. In addition, some workers tested had abnormally low total lung capacity and some had abnormally low diffusing capacity, both of which can be signs of lung disease. Although test quality was lower than desired, the high prevalence of abnormalities could not be explained by test quality. The prevalence of abnormalities was as high in good quality tests as it was in lower quality tests. Workers in areas with higher indium exposures tended to have fewer lung abnormalities than workers in areas with lower indium exposures. This finding suggests that different types of indium have different health risks and that indium air concentration alone is an inadequate measure of exposure. More sophisticated sampling and analytic methods that account for differences among indium compounds are needed. Workers hired more recently had lower blood indium concentrations and fewer lung function abnormalities, suggesting the company's efforts have had a positive impact on exposure and health. However, lung function abnormalities among workers hired more recently remained higher than expected, indicating a need for continued exposure reduction measures and ongoing medical surveillance. In a September 2010 interim report, we recommended further lowering of exposures through engineering controls, keeping indium compounds confined so that they don't contaminate other areas, and proper use, maintenance, and storage of personal protective equipment, including powered air-purifying respirators. We also recommended the use of consistent methods for air sampling, more frequent medical surveillance for newly hired workers, and improvements to the sensitivity and quality of the medical tests included in the surveillance program. Since that time, company officials have met in person with NIOSH officials and staff on two occasions to discuss a potential long-term collaboration to obtain high-quality and commercially unavailable medical testing and comprehensive exposure assessments including an engineering controls evaluation. In November 2011, the company provided NIOSH with an update on workplace changes that had been introduced since 2010 or were planned for the near future. This update made clear that the company anticipated and/ or incorporated many of the recommendations we made into its ongoing preventive efforts.