Pulmonary Squamous Cyst Induced by Exposure to Indium Arsenide in Hamsters

[Health effects of solar cell component material. Toxicity of indium compounds to laboratory animals determined by intratracheal instillations]

Owing to the increasing interest being paid to the issue of the global environment, the production of solar cells has increased rapidly in recent years. Copper indium gallium diselenide (CIGS) is a new efficient thin film used in some types of solar cell. Indium is a constitutive element of CIGS thin-film solar cells. It was thought that indium compounds were not harmful until the beginning of the 1990s because there was little information regarding the adverse health effects on humans or animals arising from exposure to indium compounds. After the mid-1990s, data became available indicating that indium compounds can be toxic to animals. In animal studies, it has been clearly demonstrated that indium compounds cause pulmonary toxicity and that the dissolution of indium compounds in the lungs is considerably slow, as shown by repeated intratracheal instillations in experimental animals. Thus, it is necessary to pay much greater attention to human exposure to indium compounds, and precautions against possible exposure to indium compounds are paramount with regard to health management.

Occupational exposure to indium: what does biomonitoring tell us?

BACKGROUND

The industrial uses of indium, a rare metal with no known physiological role in humans, have increased dramatically over the past 15 years. The results of animal toxicity studies showing pulmonary and systemic effects as well as some reports in workers have created a growing concern about the possible occurrence of toxic effects in exposed workers. Validated biomarkers to assess exposure to indium are not available.

OBJECTIVES

This work aimed at investigating the kinetics of indium in urine (In-U) and plasma (In-Pl) in workers manufacturing In ingots and mainly exposed to hardly water-soluble In compounds. All nine workers from the In department of a large metallurgical concern participated in the study as well as 5 retired workers and 20 controls.

METHODS

Personal breathing zone air was collected throughout the work shift on Monday and Friday. Blood and urine samples were collected, before and after the shift, on the same day as the air sampling and on preshift the next Monday after a non-working week-end. Moreover, rats were given either InCl(3) by intraperitoneal injection or In(2)O(3) by pharyngeal aspiration, In was followed in plasma during 120 days and measured in tissues 120 days after exposure.

RESULTS

Higher In-Pl and In-U concentrations were found in both current (range 0.32-12.61 μg/L plasma; 0.22-3.50 μg/g creat) and former (0.03-4.38 μg/L plasma; 0.02-0.69 μg/g creat) workers compared with controls (<0.03 μg/L plasma; <0.02 μg/g creat). Both biological parameters were highly correlated but no correlation was found between In-air (10-1030 μg/m(3)) and In-Pl or In-U. Normalizing In-U by the urinary creatinine concentration reduced the inter- (from 90% to 70%) and intra-individual variability (from 54% to 35%). In-Pl remained remarkably stable along the working week (inter- and intra-individual variability: 89% and 10%, respectively). Neither In-U nor In-Pl significantly increased during the day or the week. A week-end without occupational exposure was not sufficient to reach the background In-Pl and In-U levels measured in controls. The results of the experimental investigations confirmed the hypothesis that inhalation of hardly soluble In compounds may cause accumulation of In in the body leading to a prolonged "endogenous exposure" from both a lung depot of "insoluble" particles that are progressively absorbed and from a retention depot in other internal organs.

CONCLUSION

This study shows that in workers exposed to hardly soluble In compounds, In-U and In-Pl are very sensitive to detect exposure and mainly reflect long-term exposure. In-Pl levels are particularly stable for a given individual. In-U might be more influenced than In-Pl by recent exposure. Both parameters remained high years after withdrawal from exposure, indicating a possible endogenous exposure and a prolonged risk of pulmonary and systemic diseases even after work exposure has ceased.

Chronic pulmonary toxicity study of indium-tin oxide and indium oxide following intratracheal instillations into the lungs of hamsters

OBJECTIVES

The aim of this study was to clarify the chronic toxicological effects of indium-tin oxide (ITO) and indium oxide (In(2)O(3)) on laboratory animals.

METHODS

Male Syrian golden hamsters were intratracheally administered 3 mg/kg or 6 mg/kg of ITO particles, or 2.7 mg/kg or 5.4 mg/kg of In(2)O(3) particles, containing 2.2 mg/kg or 4.5 mg/kg of indium, twice a week, for 8 wk. Control hamsters were given vehicle of distilled water only. The hamsters were euthanized serially up to 78 wk after the final instillation and the toxicological effects were determined.

RESULTS

Body weight gain was significantly suppressed in the ITO 6 mg/kg-treated hamsters compared with the control group, but not in the ITO 3 mg/kg-treated or In(2)O(3)-treated hamsters. Relative lung weights among all the indium-treated groups were significantly increased compared to that in the control group throughout the observation period. The serum indium concentration among all the indium-treated groups gradually increased up to the end of the observation period. Histopathologically, foci of slight to severe pulmonary inflammatory response with diffuse alveolar or bronchiolar cell hyperplasia, expansion of the alveolar spaces and interstitial fibrotic proliferation were present in all the indium-treated hamsters and the severity of these lesions worsened with the passage of time. Lung benign adenomas were only manifest in 3 out of 15 of the ITO 6 mg/kg-treated hamsters.

CONCLUSIONS

The present results clearly demonstrate that ITO and In(2)O(3) particles caused chronic pulmonary toxicity when repeated intratracheal instillations were given to hamsters.

Genotoxicity studies of heavy metals: lead, bismuth, indium, silver and antimony

OBJECTIVES

Many kinds of heavy metals are used in industry; thus, it is important for us to clarify their toxicity. For example, lead, which is a component of solder, is notorious for its neurotoxicity, and substitute materials have been sought for many years. Therefore, we examined the genotoxicity of lead and also those of metallic bismuth, indium, silver and antimony which are possible substitutes for lead in solder.

METHODS

Bacterial reverse mutation tests and chromosomal aberration tests in cultured mammalian cells were performed according to standard procedures.

RESULTS

Antimony showed genotoxicity in both tests, and bismuth also showed positive results in the chromosomal aberration test. In contrast, lead, indium, and silver were considered to be inactive by the criteria of the present study.

CONCLUSIONS

Although further studies are needed because of the difficulty of genotoxicity evaluation using an in vitro system, sufficient precautions should be made when antimony and bismuth are used.

Toxicity of indium arsenide, gallium arsenide, and aluminium gallium arsenide

Gallium arsenide (GaAs), indium arsenide (InAs), and aluminium gallium arsenide (AlGaAs) are semiconductor applications. Although the increased use of these materials has raised concerns about occupational exposure to them, there is little information regarding the adverse health effects to workers arising from exposure to these particles. However, available data indicate these semiconductor materials can be toxic in animals. Although acute and chronic toxicity of the lung, reproductive organs, and kidney are associated with exposure to these semiconductor materials, in particular, chronic toxicity should pay much attention owing to low solubility of these materials. Between InAs, GaAs, and AlGaAs, InAs was the most toxic material to the lung followed by GaAs and AlGaAs when given intratracheally. This was probably due to difference in the toxicity of the counter-element of arsenic in semiconductor materials, such as indium, gallium, or aluminium, and not arsenic itself. It appeared that indium, gallium, or aluminium was toxic when released from the particles, though the physical character of the particles also contributes to toxic effect. Although there is no evidence of the carcinogenicity of InAs or AlGaAs, GaAs and InP, which are semiconductor materials, showed the clear evidence of carcinogenic potential. It is necessary to pay much greater attention to the human exposure of semiconductor materials.