Toxic metals

With the development of modern technology, the production of toxic metals, especially non-ferrous metals, is increasing, contaminating the air, the surface layers of the soil and are particularly dangerous when contaminating food and groundwater. Their sources are mainly metal production (pyrometallurgical and hydrometallurgical processes), exhaust gases' (tetraethylol, tetraethyl copper), fossil fuel combustion (mainly younger coal with relatively high ash content), urban waste incineration...

Lead Pb
It is a blue-silver-white soft metal. Its inorganic salts are poorly soluble in water, except acetate, nitrate, chlorate, chlorate, and to some extent chloride.

Occurrence and use
Lead is the most abundant of the heavy metals, occurring in nature as galena (lead sulphide), cerussite (lead carbonate) and anglesite (lead sulphate). It is used in the manufacture of batteries, automotive anti-knock agents (tetraethyl and tetramethyl lead), shot, cables, alloys, in the glass industry, etc.

Absorption and effects on the human body
The respiratory uptake can be estimated based on knowledge of the aerodynamic characteristics of the aerosol and on physiological respiratory parameters. About 40 % is absorbed in this way. In the GIT about 5-8 % is absorbed, in children it may be more. In animal experiments, it has been found that the use of milk, low calciuma and vitamin D, iron and fasting can increase lead absorption. In the blood, it is 98% bound to erythrocytes, has a high affinity for SH-groups, and is therefore able to inhibit enzymes (mainly enzymes of hemeu synthesis). It readily crosses the placenta and hematoencephalon. It does not accumulate in the brain. It accumulates in the bones. The haematopoietic system, nervous system, GIT and kidneys are most affected.


 * The most common form of acute poisoning is GIT involvement, anorexia, dyspepsia, constipation, colicky abdominal pain.
 * Acute encephalopathy' occurs mainly in children - apathy, drowsiness, stupor, ataxia, hyperactivity, coma and death by cardiac and respiratory arrest. It can go chronic. Diffuse atrophic changes in the cerebral cortex have been found, most prominently in the temporal and frontal lobes. The most sensitive effects of lead in children include neurobehavioral and developmental changes.
 * Effects on the PNS as a result of demyelination and degenerative changes of axons: polyneuropathy, muscle fibrillation,
 * Inhibition of heme synthesis and erythrocyte survival causes micro- or normocytic anemia, especially in occupational exposures where plumbemia reaches above 0.5 mg/l. Basophilic punctate erythrocytes and reticulocytes appear in the blood. Inhibition of haem synthesis leads to increased urinary excretion of 5-aminolevulinic acid (ALA) and coproporphyrin III.
 * In pregnant women - effects on the fetus: lower birth weight, slower CNS development, slower growth.
 * Renal damage: impaired renal tubular function, decreased glomerular filtration rate;, irreversible changes after long-term lead exposure - nonspecific nephropathy with interstitial fibrosis and tubular dilatation with atrophic changes.
 * Effect on the immune system: immunosuppression - reduction in IgD, IgM and complement production.

Therapy
Chelating agents are administered - DMSA, in mild poisoning the treatment is symptomatic, mainly sedatives (diazepam).

Arsenic As
Already Paracelsus described the clinical picture of arsenic poisoning and its treatment. In nature it is found in the form of sulfides, the most widespread is arsenopyrite. It occurs as a constituent of other ores and is obtained as a by-product of the processing of these ores. In the past it was used as a component of fertilisers, today for preserving wood against fungi, in small quantities in the pharmaceutical industry, in glass, for veterinary purposes, in some herbicides, lasers, in warfare chemicals, in alloys to improve their mechanical and physical properties, etc. Arsenic preparations have been used for therapeutic purposes in a wide range of diseases - in the treatment of lues in combination with ATBs, in sleeping sickness, amebiasis and in veterinary medicine. The use of arsenic is banned in the Czech Republic!!!!'

Arsenic is one of the oldest known poisons of the Middle Ages (prepared from arsenic). Today, poisonings are largely accidental. Preparations given parenterally are rapidly absorbed and accumulate in the liver and later in the kidneys; small amounts also accumulate in the brain, heart, uterus and muscles. Due to the high affinity of arsenic for SH-groups, significant accumulation occurs after 48 h in ectodermal tissues - skin and its adnexa (keratin, scleroprotein). Inorganic does not penetrate HEB, but penetrates the placenta and is excreted in both cow's and mother's milk.

Arsenites induce a profound disruption of oxidative phosphorylation reactions by causing energetically unfavourable oxidation of substrates, thereby damaging mitochondria, especially mitochondria of hepatocytes.

Symptoms of poisoning

 * Acute poisoning: the lethal dose is 60-80 mg. A GIT syndrome picture develops due to mesenteric capillary paralysis (As is a potent capillary-toxic poison), increased salivation, weight loss are observed. In more severe poisoning, the poisoning is accompanied by paralytic asphyctic syndrome with rapid unconsciousness and paralysis of circulation and respiration. If the person survives the acute phase, his condition is complicated by encephalitis, myelitis, nephritis or dermatitis.
 * Chronic poisoning has a varied clinical picture:
 * changes on the skin (allergic dermatitis, eczema, inflammation of the scrotum, redness, boils). Of the skin changes, it is also a typical melanosis differing from Addison's melanosis in that it does not affect the mucous membranes. Vasomotor changes, eczema, ragades, hyperkeratosis, malignant degeneration, allergic dermatitis, purplish-red smooth shiny fingers with transverse white striae of the nails.
 * neurological (polyneuritis, motor palsy, personality changes, encephalopathy, Wernike syndrome, Korsakov psychosis),
 * haematological (inhibitory effect on haematopoiesis - hypoplastic anaemia, agranulocytosis, thrombocytopenia)
 * When exposed through the respiratory tract, it causes lung cancer, and tumours of other organs (liver, kidney, bladder, skin tumours) are also common.

Further, non-specific symptoms occur - increased salivation, digestive problems, rare degenerative changes in the optics.


 * As has demonstrable teratogenic effects.

Recommended literature

 * http://arnika.org/chemicke-latky