Lead: A Hematopoietic Pollutant
Lead (= Plumbum) (Pb)
Hematopoietic pollutant
Lead is a carcinogen and teratogen for the human body. However, literature contains data confirming that it is essential for life, as it affects protein synthesis, cellular energy balance, and genetic machinery, and participates in the metabolic processes of bone tissue.
The daily requirement for the human body is 10–15 µg. A deficiency of lead in the body can develop with insufficient intake (1 µg/day or less).
Lead primarily enters the human body through the digestive tract. However, lead compounds can also enter the human body through inhaled air.
An adult human body contains about 2 mg of lead. In the gastrointestinal tract, 5–10% (and sometimes up to 50%) of the ingested lead is absorbed. The degree of lead absorption depends on the solubility of its compounds. A significant amount of lead can enter the body through inhaled air (up to 70% of aerosol containing lead settles in the lungs). At high concentrations of tetraethyl lead, there is a risk of skin penetration.
Lead levels in men are higher than in women. Normally, lead content in bones is 20 mg/kg, in the liver – 1 mg/kg, in the kidneys – 0.8 mg/kg, in the brain – 0.1 mg/kg.
Lead levels in men are higher than in women. Normally, lead content in bones is 20 mg/kg, in the liver – 1 mg/kg, in the kidneys – 0.8 mg/kg, in the brain – 0.1 mg/kg.
Lead is excreted from the body primarily through feces (80–90%), while a smaller portion is eliminated through urine.
At toxic doses, the element accumulates in the kidneys, liver, spleen, and bone tissues. In lead toxicity, primarily the hematopoietic organs (anemia), nervous system (encephalopathy and neuropathy), and kidneys (nephropathy) are affected. The hematopoietic system is particularly sensitive to lead, especially in children.
Biological role in the human body. The role of lead in the vital functions of the body is not well studied. However, literature provides data confirming (in the case of rats) that this metal is essential for animal organisms, thus, lead is currently classified as probably essential elements.
Lead deficiency in experiments reduces animal growth, disrupts iron metabolism, alters the action of certain enzymes, and changes the concentration of specific metabolites in the liver related to iron status. It has been found that lead increases growth and improves hematocrit and hemoglobin concentration in iron deficiency in rats; however, this effect was likely a result of the pharmacological action of lead. The mechanism by which lead affects iron metabolism has not yet been determined.
It is known that lead participates in the metabolic processes of bone tissue.
Toxic action of lead is largely due to its ability to form bonds with a large number of anions – ligands, including sulfhydryl groups, cysteine derivatives, imidazole and carboxyl groups, phosphates. As a result of the binding of anhydrides with lead, protein synthesis and enzyme activity, such as ATP-ase, are suppressed. Lead disrupts heme and globin synthesis by interfering with porphyrin metabolism, inducing defects in erythrocyte membranes.
Synergists and antagonists of lead. Sulfur-containing amino acids, vitamins A, C, E, B group, folic acid, niacinamide, calcium, magnesium, zinc, iron, chromium, phosphorus, and selenium help reduce lead levels in the body.
Against the background of iron deficiency, as well as calcium, phosphorus, magnesium, and zinc, the body’s ability to absorb lead increases.
Signs of lead deficiency. Data for humans are lacking. The essentiality of lead has been demonstrated under laboratory conditions in animals.
The main problem in many countries is excessive lead intake.
For all regions of Ukraine and Russia, lead is the main anthropogenic toxic element from the heavy metals group. This is associated with high industrial pollution and emissions from vehicles running on leaded gasoline. From 5% to 30% of the population in different cities suffer from lead excess.
Causes of lead excess: excessive intake (particularly under ecologically unfavorable environmental conditions: exhaust from vehicles running on leaded gasoline, production of lead paints, etc., as well as in household conditions: the action of lead-containing paint, presence of lead in children’s toys, etc.); deficiency of calcium, magnesium, zinc, and iron in the body.
Main manifestations of lead excess: increased excitability, weakness, fatigue, memory impairment; headaches; peripheral nervous system damage (pain in limbs); appearance of a lead line on the gums; dental caries, arthropathy, bone system diseases, increased blood pressure, development of atherosclerosis, abdominal pain (lead colic), spastic constipation; exhaustion, weight loss, decrease in body mass, disturbances in porphyrin metabolism (urobilinogen, coproporphyrin), nephropathy, progressive renal failure, impaired sperm motility and fertilization ability, decreased potency, reticulocytosis, increased number of erythrocytes with basophilic granularity, anemia, decreased resistance to infections (especially in children), development of saturnism syndrome, decreased levels of calcium, zinc, and selenium in the body.
In acute lead intoxication, neurological symptoms are often observed, lead encephalopathy, “lead” colic, nausea, constipation, body aches, decreased heart rate, and increased blood pressure.
In chronic intoxication, increased excitability, hyperactivity (attention deficit), depression, decreased IQ (intelligence quotient), hypertension, peripheral neuropathy, loss or decrease of appetite, stomach pain, anemia, nephropathy, “lead line,” muscle dystrophy of the hands, etc.
- At lead concentrations in children’s whole blood of 10–20 µg/100 ml, developmental disorders are noted.
- At corresponding concentrations from 20 to 40 µg/100 ml, a decrease in IQ is observed.
- At lead concentrations in whole blood of adults and children from 40 to 60 µg/100 ml, anemia and peripheral neuropathy are noted.
- At lead concentrations in whole blood of adults from 60–80 µg/100 ml, chronic nephropathy is observed.
- At corresponding concentrations from 80–100 µg/100 ml, acute nephropathy is noted.
- At concentrations from 100–120 µg/100 ml – encephalopathy.
Lead is necessary: in cases of decreased hematocrit and hemoglobin, in all iron deficiency states.
Dietary sources of lead: vegetables and fruits (especially — ginger root, cherries, pears, viburnum, black rowan, red currants, sweet cherries, blueberries), nuts and seeds (sesame, almonds), legumes: beans, peas; wheat bran; mushrooms (especially — butter mushrooms); canned goods in tin containers, fresh and frozen fish, gelatin.