Bismuth is classified as moderately toxic to the human body ultra-trace elements. It affects the formation of “tanning pigment” – melanin – and participates in ossification processes.
The daily requirement for the human body is not precisely established, but there are data suggesting that the optimal average daily intake of bismuth is 5–20 µg.
The toxic and lethal doses for humans have not been determined. Chronic intake of bismuth in amounts of 1–1.5 g per day is considered dangerous.
Bismuth enters the human body mainly through food, as well as from air and water. The absorption of bismuth that enters the gastrointestinal tract is minimal, approximately 5%. After absorption, bismuth is found in the blood as compounds with proteins and also penetrates into erythrocytes. Bismuth is distributed relatively evenly between organs and tissues. Some accumulation of bismuth may be observed in the liver, kidneys (up to 1 µg/g), spleen, and bones. Bismuth also accumulates in the brain.
Bismuth that has passed through the gastrointestinal tract is excreted as bismuth sulfide, coloring the stool dark. Absorbed bismuth is excreted in urine.
Biological role in the human body. Little is known about the physiological role of bismuth. Current knowledge allows us to conclude that there is no significant physiological role of bismuth in the human body. Bismuth may induce the synthesis of low-molecular-weight proteins, participate in ossification processes, and form intracellular inclusions in the epithelium of renal tubules. It is possible that this element has genotoxic and mutagenic properties.
Bismuth influences the formation of “tanning pigment” – the dark brown pigment melanin, which deactivates free radicals that arise after the body is exposed to ultraviolet and ionizing radiation, as well as as a result of certain enzymatic processes and auto-oxidation reactions.
Bismuth belongs to the category of heavy metals; it is a moderately toxic element. Some sources even refer to bismuth as a “harmful” heavy metal. Being very similar in properties to lead, bismuth is much less toxic. In this regard, ecologists advocate for the gradual replacement of lead with bismuth in industrial and manufacturing processes.
Soluble bismuth salts are toxic and, in terms of their action, are similar (though to a lesser extent) to mercury salts. There are very few water-soluble bismuth salts, and consequently, the likelihood of encountering them is low.
The bismuth salts used in medicine are practically insoluble in water, applied in the form of colloidal solutions, and do not have high toxicity. However, with prolonged or intensive use of bismuth-containing preparations, complications may arise. One of the main manifestations is the so-called “bismuth line” – inflammation caused by the deposition of bismuth sulfide at the edges of the gums. Disorders may also occur in the urinary tract.
The carcinogenicity of bismuth has not been established.
Professional poisoning or skin diseases when working with bismuth are almost indistinguishable. However, chronic bismuth poisoning can lead to changes in protein, carbohydrate, and lipid metabolism, a decrease in hemoglobin levels in the blood, and other disorders.
Synergists and antagonists of bismuth. Unknown.
Signs of bismuth deficiency: data on clinical manifestations caused by bismuth deficiency are absent.
Increased bismuth levels in the body. Intoxication is usually observed only with prolonged exposure to bismuth salts in large doses. However, cases of iatrogenic, occupational, and domestic poisoning do occur.
The mechanism of bismuth’s toxic action is poorly studied. It has been established that poisoning with bismuth salts affects the kidneys, central nervous system, liver, skin, and mucous membranes.
Prolonged use of bismuth preparations in large doses may cause symptoms of “bismuth” encephalopathy (especially in patients with impaired kidney function).
Main manifestations of excess bismuth: memory impairment, insomnia, signs of nervous system damage (sensitivity disorders, neck rigidity), weakness of cardiac activity, arrhythmia, appearance of a dark line around the gums, pigmentation of the mucous membranes of the gums and oral cavity; stomatitis, pharyngitis, difficulty swallowing; salivation, nausea, vomiting, abdominal pain, bloating, diarrhea; toxic hepatitis with fatty degeneration and cirrhosis; albuminuria, cylinders in urine, “bismuth” dermatitis, loss of appetite, fatigue, weight loss.
Bismuth is necessary: bismuth compounds have found application in medicine. Bismuth subgallate, when applied to the skin and mucous membranes, causes the coagulation of colloids in extracellular fluid, mucus, exudate, and forms a protective film that protects the endings of sensitive nerves from irritation and can reduce pain sensations and prevent the development of edema.
Bismuth subnitrate in the form of ointments and powders is used as a protective and anti-inflammatory agent for dermatitis, eczema, erosions, and ulcers of the skin. When administered orally in the form of suspensions, gels, or tablets, bismuth salts (bismuth subsalicylate, bismuth subcitrate and several others) form a protective film on the surface of the mucous membranes of the gastrointestinal tract – chelate compounds with a protein substrate. This film helps to reduce local inflammatory processes, heal peptic ulcers, and decrease the number of relapses. Bismuth preparations have antibacterial action (suppress the growth of Helicobacter pylori).
Combined preparations containing bismuth subnitrate (Vikalin, Vikaire) have astringent, anti-acid, and mild laxative effects. Bismuth compounds are used in inflammatory diseases of the stomach and intestines, gastric and duodenal ulcers, diarrhea of various origins, etc.
Dietary sources of bismuth: the intake of bismuth into the body from water or food is minimal. It is much more likely that bismuth enters the body from medicinal preparations when taken orally or through the skin (in case of external application).