Bismuth is a naturally occurring heavy metal that is found as a trace element in the earth's crust. Bismuth has been used historically in medicines, cosmetics, and industrial applications. But is this metal toxic to humans?
In its pure elemental form, bismuth is considered very safe and non-toxic for humans. In fact, it is one of the few heavy metals that has low toxicity. Bismuth compounds can have varying degrees of toxicity depending on the exact compound, with some being more toxic than others.
Bismuth's low toxicity and density similar to lead has meant it's been used as a replacement for lead in products like paint, ceramics, and hunting shot. Unlike lead, bismuth is not absorbed by the body so it does not accumulate in soft tissues or bones. Most bismuth compounds pass through the body quickly when ingested.
One of the most common bismuth compounds is bismuth subsalicylate, better known as the active ingredient in Pepto-Bismol. Bismuth subsalicylate is considered very safe when used as directed for treating temporary stomach upset, heartburn, nausea, and diarrhea. The recommended doses and short-term usage carry very little risk.
Higher doses of bismuth subsalicylate taken for prolonged periods can occasionally cause side effects like darkening of the tongue and stool, ringing in the ears, headache, dizziness, and difficulty concentrating. Very high doses may lead to kidney damage and neurotoxicity. But typical Pepto-Bismol dosages are well below safety limits for most adults.
Other bismuth compounds like bismuth oxychloride and bismuth subnitrate are used in some cosmetic products. Though considered far less toxic than many other metals and ingredients in cosmetics, bismuth compounds can still cause allergic skin reactions in some people with continued exposure. There are also concerns about trace amounts of elemental bismuth accumulating with repeated use.
Occupational overexposure is one of the biggest concerns with bismuth toxicity in humans. Workers involved in smelting, alloy production, or other industrial processes may inhale bismuth dust or fumes. Breathing high levels of bismuth can potentially cause lung and kidney damage, though reported cases are rare. Strong safety precautions are used to protect workers from excessive bismuth exposure.
So, bismuth in its pure form and the amounts found in Pepto-Bismol are considered very safe. But some bismuth compounds are moderately toxic with excessive dosage or prolonged exposure, especially through inhalation. While not as dangerous as other heavy metals like lead and arsenic, bismuth should still be handled carefully, especially in occupational settings with repeated exposure. As with any substance, the dose and route of exposure plays a big role in the potential toxicity of bismuth.
