Application of the ICRP respiratory tract model to estimate pulmonary retention of industrially sampled indium-containing dusts

Abstract

Inhalation of indium-containing dusts is associated with the development of indium lung disease. Workers may be exposed to several different chemical forms of indium; however, their lung dosimetry is not fully understood. We characterized the physicochemical properties and measured the lung dissolution kinetics of eight indium-containing dusts. Indium dissolution rates in artificial lung fluids spanned two orders of magnitude. We used the International Commission on Radiological Protection (ICRP) human respiratory model (HRTM) to estimate pulmonary indium deposition, retention and biokinetic clearance to blood. For a two-year (median workforce tenure at facility) exposure to respirable-sized particles of the indium materials, modeled indium clearance (>99.99% removed) from the alveolar-interstitial compartment was slow for all dusts; salts would clear in 4 years, sintered indium–tin oxide (ITO) would clear in 9 years, and indium oxide would require 48 years. For this scenario, the ICRP HRTM predicted that indium translocated to blood would be present in that compartment for 3.5–18 years after cessation of exposure, depending on the chemical form. For a 40-year exposure (working lifetime), clearance from the alveolar–interstitial compartment would require 5, 10 and 60 years for indium salts, sintered ITO and indium oxide, respectively and indium would be present in blood for 5–53 years after exposure. Consideration of differences in chemical forms of indium, dissolution rates, alveolar clearance and residence time in blood should be included in exposure assessment and epidemiological studies that rely on measures of total indium in air or blood to derive risk estimates.

Two-year follow-up of exposure, engineering controls, respiratory protection and respiratory health among workers at an indium-tin oxide (ITO) production and reclamation facility

“…To that end, rotary bond was one the only department that had decreased per cent person-days with any observed respirator use and decreased average per cent time respirator use during 2014 compared with 2012; however, ITO had increased per cent person-days with any observed respirator use and increased average per cent respirator use in 2014, suggesting additional factors besides respirator use are contributing to the observed discrepancies. Furthermore, various forms of indium have different dissolution times from the lungs and blood that are further affected by tenure, indium stored in the lungs and other organs, and other factors which could in part account for these discrepancies 16. For Rotary Grinding, the decrease in In resp from 2012 to 2014 was modest and likely attributable in part to the engineering control of primary control mist collectors being added to each unit to remove contaminants, yet the average ∆In P was the second highest increase of any department; this discrepancy could reflect the small number of workers in Rotary Grind or historical exposure.…”

NIOSH’s Respiratory Health Division: 50 years of science and service

“…56,57 RHD found evidence of evolving lung function abnormalities that appeared to be more common in workers with higher indium exposures. 58 This HHE led to a multidisciplinary NIOSH research study that characterized the in vivo toxicity and physicochemical properties of production materials, 59,60 as well as the quantitative relationship between indium exposure and early biomarkers of indium lung disease. 61,62…”

Indium oxide nanoparticles induce lung intercellular toxicity between bronchial epithelial cells and macrophages

“…In the upper parts of the lungs, the indium compound is likely to remain as solid particles; however, the particles tend to penetrate into the deeper lungs slowly (Andersen, Cropp, & Paradise, 2017). Furthermore, once the indium compound enters the human body, the retention time can reach 5‐10 years or even 60 years (Stefaniak, Virji, Badding, & Cummings, 2017).…”