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Original Research: COPD |

Five-Year Cohort StudyFive-Year Cohort Study of Indium-Exposed Workers: Emphysematous Progression of Indium-Exposed Workers

Makiko Nakano, MD, PhD; Kazuyuki Omae, MD, PhD; Kazuhiko Uchida, MD, PhD; Takehiro Michikawa, MD, PhD; Noriyuki Yoshioka, DVM; Miyuki Hirata, PhD; Akiyo Tanaka, DVM, PhD
Author and Funding Information

From the Department of Preventive Medicine and Public Health (Drs Nakano, Omae, Uchida, Michikawa, and Yoshioka), School of Medicine, Keio University, Tokyo; Environmental Epidemiology Section (Dr Michikawa), Center for Environmental Health Sciences, National Institute for Environmental Studies, Tsukuba; and Environmental Medicine (Drs Hirata and Tanaka), Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.

CORRESPONDENCE TO: Makiko Nakano, MD, PhD, Department of Preventive Medicine and Public Health, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 1608582, Japan; e-mail: nakano.makiko@z8.keio.jp


FUNDING/SUPPORT: This study was supported by Grants-in-aid for Scientific Research (Project Nos. 15390191, 17390179, 20249039, and 23249033) from the Ministry of Education, Culture, Sports, Science and Technology of Japan [2003-4, 2005-6, 2008-10, and 2011] and in part by donations for research in preventive and environmental medicine from two of the surveyed companies.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;146(5):1166-1175. doi:10.1378/chest.13-2484
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BACKGROUND:  Dose-dependent adverse lung effects due to indium exposure have been reported in a cross-sectional study. This is a 5-year longitudinal cohort study of indium-exposed and unexposed workers, assessing indium exposure levels and its clinical lung effects.

METHODS:  From 2008 to 2011, a 5-year follow-up study was conducted on 40 unexposed and 240 workers formerly or currently exposed to indium at 11 factories. Indium exposure was assessed by serum indium (In-S) (μg/L). Lung effects were assessed by subjective symptoms, serum biomarkers, spirometry, and chest high-resolution CT scan. Effect biomarkers used were Krebs von den Lungen and surfactant protein D.

RESULTS:  Mean values of In-S, Krebs von den Lungen, and surfactant protein D among the workers exposed to indium at baseline declined during the 5-year follow-up by 29.8%, 27.2%, and 27.5%, respectively. Of the exposed subjects with In-S levels > 20 μg/L, 26.3% experienced emphysematous progression on high-resolution CT scan. Ninety percent (18 of 20) of workers with emphysematous progression during follow-up were current smokers at baseline, and a trend of increasing incidence of emphysematous progression at higher In-S levels was observed among the smokers (P = .005). Emphysematous changes among subjects with In-S levels > 20 μg/L were likely to progress, after adjusting for age, mean duration since initial indium exposure, and smoking history (OR = 10.49, 95% CI = 1.54-71.36).

CONCLUSIONS:  Long-term adverse effects on emphysematous changes were observed. The results suggest workers exposed to indium with In-S levels > 20 μg/L should be immediately removed from exposure.

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