Indium

Indium (In) compounds are poorly absorbed when ingested and moderately so when inhaled, insoluble particle absorption is highly dependent on particle size. Muscle, skin, and bone constitute the main storage sites, but the excretion routes vary depending on the form: ionic indium is excreted primarily in urine; and fecal elimination is the predominant route for removal of colloidal indium. A biphasic pattern of excretion and a whole-body biological half-time in the order of 2. weeks have been reported for both forms of indium. However, in workers exposed to poorly soluble indium compounds, half-times up to approximately 9. years for serum indium were seen, probably because of the slow release of indium from pulmonary tissues.Ionic indium is concentrated in the kidneys, producing renal failure; colloidal indium is taken up by the reticuloendothelial system, causing damage to the liver and spleen. Ionic indium has been shown to produce marked ultrastructural damage to the endoplasmic reticulum of both hepatocytes and renal proximal tubule cells, with associated disruption of heme metabolism and hemoprotein function.The intravenous administration of ionic indium to pregnant hamsters is reported to produce malformations of the fetal digits.The most common routes of exposure for the general population are inhalation and ingestion; for occupationally exposed persons, it is inhalation. Following the expansion of the industrial use of indium, a series of cases and epidemiological studies revealed that interstitial lung disease with subsequent progressive emphysema and pulmonary alveolar proteinosis occurred in occupationally exposed workers. There was a dose-response relationship between serum indium and biomarkers of interstitial lung disease or findings of subsequent progressive emphysema on chest high resolution computed tomography among indium workers. Given the serious lung disease found in indium workers, occupational health organizations in the United States and Japan have recently decreased occupation exposure limits to reduce worker harm.