Pulmonary fibrosis in an individual occupationally exposed to inhaled indium-tin oxide

Abstract

Despite the increasing industrial use of indium-tin oxide (ITO) to manufacture flatpanel displays, such as liquid-crystal displays or plasma display panels for televisions, little is known about the potential health hazard induced by occupational exposure to indium compounds.The current study describes a case of fibrotic lung disease that developed after a 4-yr exposure to ITO. The pathology of the lung demonstrated pulmonary fibrosis with the presence of cholesterol granulomas.In conclusion, more attention needs to be paid to the possible toxic effects of indium compounds, and maximum healthcare measures should be taken to protect industry workers from these toxicities.KEYWORDS: Cholesterol granuloma, human, indium-tin oxide, lung injury, pulmonary fibrosis I ndium belongs to Group III in the periodic table and is mainly used in the manufacture of flat-panel displays, such as liquid-crystal displays or plasma display panels for television screens, computer screens and video monitors [1,2]. In these displays, indium-tin oxide (ITO) is utilised for transparent conductive films. In light of the recent growth of the market due to the increasing use of liquid-crystal displays in personal computer screens and plasma display panels in wall-mounted televisions, the demand for ITO has risen sharply. As industrial consumption of ITO rises, the potential health hazard caused by occupational exposure to indium compounds has been attracting much more attention than before. However, in the literature, there have been a limited number of reports of pulmonary toxicity by ITO, including only one autopsied human case with occupational exposure to indium compounds [3], and a few preliminary animal studies on the lung toxicity of indium [4][5][6][7][8][9]. In the present study, a previously healthy young male with lung injury, probably caused by inhalation of ITO, is described. CASE PRESENTATIONIn January 2002, a 30-yr-old male engineer visited the current authors' hospital (Dept of Respiratory Medicine, Respiratory Centre, Toranomon Hospital, Tokyo, Japan) complaining of dry cough and exertional dyspnoea, which he had been experiencing since 1997. He had a minimum history of cigarette smoking (3 cigarettes?day -1 for 3 yrs). From 1994 to 1998, he had been exposed to indium compounds (i.e. ITO) as an aerosol while making transparent conductive films. Physical examination of the chest on admission revealed normal vesicular breath sounds and the absence of finger clubbing. Pulmonary function tests and arterial blood gas analysis in room air yielded normal values: a vital capacity of 4.18 L (93% predicted), forced expiratory volume in one second of 3.07 L (73% pred), residual volume (RV) of 2.20 L (measured by the gas dilution method; 158% pred), total lung capacity (TLC) of 6.38 L (109% pred), RV/TLC ratio of 34%, carbon dioxide diffusing capacity of the lung of 3.21 mL?min -1 ?kPa (89% pred), pH 7.40, arterial oxygen tension of 11.8 kPa, and arterial carbon dioxide tension of 5.3 kPa [10]. Peripheral blood examination sho...

Chronic Pulmonary Toxicity Study of Indium‐Tin Oxide and Indium Oxide Following Intratracheal Instillations into the Lungs of Hamsters

“…Following the first case report involving death 13) , a second case of lung disease related to inhaled ITO was reported in 2005 18) . A worker developed pulmonary fibrosis and emphysema after a 4-yr occupational exposure to ITO.…”

Indium Chloride‐induced Micronuclei in In Vivo and In Vitro Experimental Systems

“…ITO exposure in the work environment generates interstitial pneumonia [1][2][3] . Since indium continues to be used in various industries, it is necessary to clarify the carcinogenicity of indium compounds.…”

“…However, there have been cases of death due to interstitial pneumonia that are thought to have been caused by indium-tin oxide (ITO) inhalation 1) , and interstitial lung disease has been reported in workers handling ITO [1][2][3] . A recent study reported the carcinogenicity of indium (III) phosphide (InP), which is a compound used in semiconductors, and severe lung damage has also been reported to be associated with other indium compounds as well as InP 4) .…”

Causal Relationship between Indium Compound Inhalation and Effects on the Lungs

“…In this study, we combined three sets of baseline data, namely data reported by Hamaguchi et al 12) , those reported by Chonan et al 13) , and other newly collected unpublished data, because all three sets of data showed the same consequences. Seven indium lung cases have been discovered [7][8][9][10][11] . Therefore, the consistency of association criterion seems to be fulfilled.…”

“…After a detailed medical examination, he was diagnosed with interstitial pneumonia, possibly caused by the inhalation of ITO particles. Up to the end of 2008, seven indium-induced cases of lung injury were disclosed [7][8][9][10][11] . After the first case was found, two epidemiological studies were performed in two different populations of indium-exposed workers 12,13) .…”