Bismuth

Bismuth is used in alloys, semiconductor elements, cosmetics, and pharmaceuticals. Due to its low toxicity, the uses of bismuth as an alternative to lead are expanding. Bismuth-containing medicines have been applied to humans for more than 200 years, mainly as gastrointestinal drugs to protect the gastrointestinal mucosa, and recently to eradicate Helicobacter pylori. As the amounts of bismuth intake from water and food are negligible, exposure to bismuth occurs through dosing with bismuth-containing medicines. Humans have experienced bismuth intoxication, including fatal cases, due to bismuth medications in the past 100 years. The gastrointestinal absorption rates of bismuth medicines are less than 1%, and the small amount of absorbed bismuth is rapidly excreted in the urine at therapeutic doses. Overdosing of bismuth compounds causes acute renal dysfunction. In the 1970s, outbreaks of a reversible neurological disease called bismuth encephalopathy occurred in patients who had ingested large doses of bismuth for an extended period of time. However, because many other people who also consumed large amounts of bismuth did not develop symptoms, the dose–response relationship between bismuth intake and these symptoms remains unclear. Conditions in the gastrointestinal tract, including the presence of thiols, pH, or gut microbiota, might have enhanced the absorption of bismuth, but the mechanisms remain unclear. Various bismuth nanoparticles for tumor imaging and therapy have been developed in recent years. These nanoparticles were administered directly into the bloodstream, and therefore the fates and toxicity of the bismuth liberated from the nanoparticles need further research.