Sintered indium-tin-oxide (ITO) particles: a new pneumotoxic entity

Area of Science:

• Toxicology
• Materials Science
• Occupational Health

Background:

• Indium-Tin-Oxide (ITO) is a sintered mixture of indium oxide (In(2)O(3)) and tin oxide (SnO(2)) (90:10 wt:wt).
• Recent reports link ITO exposure to interstitial pulmonary diseases in manufacturing workers.
• The specific toxic component and mechanisms of ITO-induced lung injury remain unclear.

Purpose of the Study:

• To identify the exact chemical component responsible for ITO toxicity.
• To investigate the mechanisms underlying ITO's toxicological effects.
• To compare the in vivo and in vitro reactivity of ITO with its components and unsintered mixture.

Main Methods:

• In vivo studies involved pharyngeal administration of ITO, In(2)O(3), SnO(2), or a mixture (MIX) to rats.
• In vitro cytotoxicity assays were performed on lung epithelial cells (RLE) and macrophages (NR8383).
• Reactive oxygen species (ROS) production was assessed using electron paramagnetic resonance spectrometry.

Main Results:

• ITO particles induced a significant and persistent inflammatory reaction in rat lungs, more pronounced than individual oxides or MIX.
• ITO exhibited strong cytotoxicity towards macrophages in vitro, while epithelial cells remained largely unaffected.
• ITO exposure led to increased micronuclei in type II pneumocytes in vivo, suggesting genotoxic potential, and ROS production via Fenton-like activity.

Conclusions:

• The sintering process is critical for ITO's unique toxicological properties, creating a specific toxic entity.
• ITO induces inflammatory and genotoxic responses, necessitating strict industrial exposure controls.
• ITO's toxicity is mediated by ROS production and affects macrophages more severely than lung epithelial cells.