Arsenic (= Arsenic) (As)
The main weapon of poisoners or a sexual stimulant?
Arsenic is classified as conditionally essential, immunotoxic for the human body elements.
Since ancient times, arsenic has been known both as a medicine and as a poison. In Rome, the poisons of Locusta were famous; in Venice, for example, the court employed specialists in poisoning. And the main component of almost all poisons was arsenic. There is a hypothesis that Napoleon was poisoned with arsenic compounds on the island of Saint Helena.
Symptoms of arsenic poisoning – a metallic taste in the mouth, vomiting, severe abdominal pain, later – convulsions, paralysis, death.
Currently, it has been established that in small doses, arsenic is necessary for the human body: it prevents the loss of phosphorus. Just as vitamin D regulates phosphorus-calcium metabolism, arsenic regulates phosphorus metabolism.
However, if the concentration of arsenic in food or soil exceeds the threshold and approaches toxic doses, the number of fatalities caused by cancers of the larynx, eyes, or leukemia will increase.
The daily requirement for the human body is 12–15 µg. A deficiency of this element in the body can develop with insufficient intake (1 µg/day or less).
The human body contains about 15 mg of arsenic.
Arsenic compounds enter the human body through drinking and mineral water, grape wines and juices, seafood, medicinal preparations, pesticides, and herbicides.
About 80% of arsenic is absorbed in the gastrointestinal tract, 10% enters through the lungs, and about 1% – through the skin.
More than 90% of inorganic arsenic compounds are soluble and well absorbed. Subsequently, inorganic arsenic is transported to the liver, where it is methylated. Arsenic accumulates in the lungs, liver, skin, and small intestine. Arsenic is primarily deposited in the reticuloendothelial system, likely due to the binding of arsenite to the SH-groups of proteins, which are relatively more abundant in these tissues.
After 24 hours, 30% of arsenic is excreted from the body with urine and about 4% – with feces. Minor amounts are eliminated with sweat, shed hair, sloughed skin, and bile.
Biological role in the human body. It is known that arsenic interacts with thiol groups of proteins, cysteine, glutathione, and lipoic acid. Arsenic may participate in some enzymatic reactions. As an enzyme activator, arsenic likely acts as a phosphate substitute. As an inhibitor, arsenic apparently reacts with the sulfhydryl groups of enzymes.
Arsenic affects oxidative processes in mitochondria, participates in nucleic acid metabolism, i.e., has a direct relation to protein synthesis, and is necessary for hemoglobin synthesis, although it is not part of its composition.
It is known that in mammals, arsenic exists in reduced forms As, NaAs3+, which are considered potential stimulators of metallothionein formation with CdCl2.
It was believed that “microdoses of arsenic, cautiously introduced into a growing organism, promote the growth of bones in humans and animals in length and thickness; in some cases, bone growth can be induced by microdoses of arsenic even after the end of overall growth.” However, these data have not found scientific confirmation.
Currently, the effect of microdoses of arsenic-containing drugs as anticancer agents is being studied.
Synergists and antagonists of arsenic. Arsenic can accumulate intensively in the body in the case of
selenium deficiency, thereby contributing to selenium deficiency.
Antagonists of arsenic include
sulfur,
phosphorus,
selenium, vitamins C, E, and amino acids.
Arsenic inhibits the absorption of
zinc, selenium, ascorbic acid, vitamins A and E, and amino acids.
Signs of arsenic deficiency: in humans – dermatitis, anemia; in animals – reduced growth and abnormal reproduction, characterized by high perinatal mortality.
Other known symptoms: decreased concentration of triglycerides in serum.
The target organs in cases of excessive arsenic content in the body are the bone marrow, gastrointestinal tract, skin, lungs, and kidneys. Arsenic and all its compounds are toxic to varying degrees.
Arsenic belongs to the so-called “thiol poisons”. The mechanism of its toxicity is associated with the disruption of sulfur, selenium, and phosphorus metabolism. The toxicity of arsenic depends on its chemical properties and decreases in the following order: arsine AsH3 > inorganic As3+ > organic As3+ > inorganic As5+ > arsenonium compounds AsH4+ > elemental arsenic.
There is sufficient evidence of the carcinogenicity of inorganic arsenic compounds. A high lung cancer mortality rate has been recorded among workers engaged in pesticide production, gold mining, and the smelting of arsenic alloys with other metals, as well as non-ferrous metals and especially copper. As a result of prolonged consumption of arsenic-contaminated water or medicinal preparations, the development of poorly differentiated skin cancer (Bowen’s disease) is often observed. It is likely that hepatic hemangioendothelioma is also an arsenic-dependent tumor.
A slight excess of arsenic in the diet causes abnormal fertility in animals, characterized by a significant increase in sexual activity and fertility.
The technogenic ecological disaster in southern India received wide publicity – due to increased water extraction from aquifers, arsenic began to enter drinking water. This caused toxic and oncological damage to tens of thousands of people.
Causes of arsenic excess: excessive intake (constant contact with arsenic, environmental pollution, smoking, excessive consumption of grape wine, prolonged administration of salvarsan preparations), disruption of arsenic metabolism regulation; enhanced accumulation of arsenic in the body in selenium deficiency.
Main manifestations of arsenic excess: irritability, headaches, liver dysfunction, development of fatty hepatosis; skin allergic reactions, eczema, dermatitis, itching, ulcers, skin depigmentation, palmar-plantar hyperkeratosis; conjunctivitis; respiratory system lesions (fibrosis, allergies, perforation of the nasal septum, tumors); vascular lesions (primarily – lower extremities – endoangiitis) nephropathy, increased risk of skin, liver, and lung neoplasms.
In acute arsenic poisoning, abdominal pain, vomiting, diarrhea, and central nervous system depression are observed; intravascular hemolysis, acute renal and liver failure, cardiogenic shock develop. The similarity of arsenic poisoning symptoms with cholera symptoms allowed the successful use of arsenic compounds (most often – arsenic trioxide) as a lethal poison for a long time.
In areas where there is an excess of arsenic in soil and water, it accumulates in the thyroid gland in humans and causes endemic goiter.
Arsenic is carcinogenic in small doses. However, for a long time (until the mid-1950s), it was used as a medicine to “improve the blood.” Such use often led to the development of oncological diseases.
Long-term consequences of arsenic intoxication: decreased hearing acuity in children, nervous system damage (encephalopathy, speech disorders, coordination of movements, convulsions, psychoses, polyneuropathies with pain syndrome), muscle trophic disorders, immunodeficiency.
Arsenic is necessary: in inflammatory processes caused by protozoan and microbial damage, in some forms of allergies, in anemia, to increase appetite.
In cases of poisoning of humans or domestic animals (dogs, birds, pigs, cows) with large doses of selenium, arsenic acts as an antidote. In experiments conducted on mice, it was possible to reduce cancer morbidity specifically with the help of specially selected doses of arsenic.
Arsenic-containing mineral waters are used in the treatment of anemia and some gastrointestinal diseases. It is part of mumiyo – a natural mineral-organic substance. It is also used in the treatment of sleeping sickness in the last stage.
Dietary sources of arsenic: fish, shellfish, shrimp, krill, lobsters,
laminaria (seaweed),
wild rice, grains and cereal products,
lentils,
carrots,
grapes,
strawberries,
raisins. Significant amounts of arsenic are found in fish oil and marine fish (up to 10 mg/kg), and wines (up to 1 mg/L or more).
In water, arsenic levels are typically less than 10 µg/L; however, in some regions of the world (India, Bangladesh, Taiwan, Mexico), the concentration of this element exceeds 1 mg/L, which causes mass chronic arsenic poisoning and triggers the so-called “blackfoot disease.”