Indium lung is a rare occupational lung disease caused by exposure to respirable indium in the form of indium tin oxide. It is classified as an interstitial lung disease (diffuse parenchymal lung disease).
Signs and symptoms
The major signs of indium lung are pulmonary alveolar proteinosis and pulmonary fibrosis. Symptoms include dyspnea (shortness of breath), cough, and increased sputum production. Hemoptysis has also been seen in people with indium lung. Other symptoms seen in some but not all cases include digital clubbing, low DLCO (capacity to move oxygen from the alveoli into the blood), and lowered forced expiratory volume. Emphysema has been associated with indium lung, but may not be part of the syndrome.
Lung cancer may be related to indium lung disease, though indium is not a known carcinogen.
Indium lung is caused by exposure to indium tin oxide in a variety of occupational contexts, including reclamation and production. Exposure to indium tin oxide as it reacts can lead to exposure to indium metal, indium hydroxide, and indium oxide.
The exact mechanism of pathogenesis is unknown, but it is hypothesized that indium may exacerbate existing autoimmune disorders or that phagocytosis of indium by alveolar macrophages may cause dysfunction in the macrophages.
CT scanning and radiography can be used to aid in the diagnosis of indium lung. CT abnormalities include ground-glass opacities, interlobular septal thickening, honeycombing, and bronchiectasis.
Multiple abnormal laboratory findings have been noted in indium lung. High levels of serum indium have been found in all cases of indium lung. Other abnormal laboratory values that have been found include elevated alanine aminotransferase, elevated aspartate aminotransferase, elevated C-reactive protein, elevated interstitial lung disease markers, and elevated GM-CSF autoantibodies.
The National Institute of Occupational Safety and Health, Japan (JNIOSH) set limits for acceptable exposure at 0.0003 mg/m3 after the discovery of indium lung. Methods for reducing indium exposure are thought to be the best mode of protection. Medical surveillance of indium workers is also a method of prevention.
Prognostic factors were a matter of research as of 2012, but preliminary evidence suggests that duration of employment and reported use of respiratory protection are not prognostic factors, but the serum level of indium may be a prognostic factor - higher levels of serum indium have been associated with worse prognoses. Indium lung disease has been fatal in several cases.
Cases have been reported in Japan, the United States, and China. The indium industry is mainly based in Japan, where the bulk of cases have occurred; indium industry is also present in the US, China, Taiwan, and South Korea. As of 2010, 10 cases had been described, though more than 100 indium workers had documented respiratory abnormalities.
- Sauler, Maor; Gulati, Mridu (December 2012). "Newly Recognized Occupational and Environmental Causes of Chronic Terminal Airways and Parenchymal Lung Disease". Clinics in Chest Medicine. 33 (4): 667–680. doi:10.1016/j.ccm.2012.09.002. PMC 3515663. PMID 23153608.
- Cummings, Kristin J.; Nakano, Makiko; Omae, Kazuyuki; Takeuchi, Koichiro; Chonan, Tatsuya; Xiao, Yong-long; Harley, Russell A.; Roggli, Victor L.; Hebisawa, Akira (June 2012). "Indium Lung Disease". Chest. 141 (6): 1512–1521. doi:10.1378/chest.11-1880. ISSN 0012-3692. PMC 3367484. PMID 22207675.
- The Technical Guideline for Preventing Health Impairment of Workers Engaged in the Indium Tin Oxide Handling Processes (PDF). JNIOSH. 2010.
- Homma, Toshiaki; Ueno, Takahiro; Sekizawa, Kiyohisa; Tanaka, Akiyo; Hirata, Miyuki (May 2003). "Interstitial pneumonia developed in a worker dealing with particles containing indium-tin oxide". Journal of Occupational Health. 45 (3): 137–139. doi:10.1539/joh.45.137. ISSN 1341-9145. PMID 14646287.
- Cummings, Kristin J.; Donat, Walter E.; Ettensohn, David B.; Roggli, Victor L.; Ingram, Peter; Kreiss, Kathleen (March 1, 2010). "Pulmonary alveolar proteinosis in workers at an indium processing facility". American Journal of Respiratory and Critical Care Medicine. 181 (5): 458–464. doi:10.1164/rccm.200907-1022CR. ISSN 1535-4970. PMC 3159086. PMID 20019344.
- Badding, MA; Stefaniak, AB; Fix, NR; Cummings, KJ; Leonard, SS (2014). "Cytotoxicity and characterization of particles collected from an indium-tin oxide production facility". Journal of Toxicology and Environmental Health. Part A. 77 (20): 1193–209. doi:10.1080/15287394.2014.920757. PMC 4192900. PMID 25208660.