Selenium belongs to VIa group of Periodic table of the elements. Selenium is in group of semi-metals. Selenium exists in several allotropic modifications like: grey, red and black selenium, where the grey selenium is the most stable. Selenium occurs in Earth crust in minerals which consist selenium. Selenium is using in elementary shape or like salts in electronics and at xerox, in production of glass, pigments, chemicals, drugs, fungicides, electrical devices and in rubber industry.
Origin in water
Selenium occurs in soil as iron- selenite, calcium-selenite and as elementary selenium. Sedimentary rocks comprehend more selenium then limestone or sandstone. Quantities depend from geographic area.
Vitamin E and selenium are together stronger then total of their individually effect. They are oxidants and they prevent aging and tissue hardens with oxidation. Selenium is important for production of glutathione -peroxides, the primary corporal anti-oxidants in all cells.
"Factor 3" is important selenium compounds (active selenium) which has preventive effect on liver, immunity rising, prevents effect of mercury, arsenic, cadmium and involves in keeping of tissues elastic. Selenium gives protection against cancers. It helps in preservation of tissue elastic. It reduces heat waves and hardship of menopause. It helps in prevention of dandruff making. Selenium raises spermatozoids number and man fecundity.
Studies on animals confirm efficiency in prevention of endemic diseases. At animals selenium causes acute and chronic toxicities with large concentrations, which results congenital muscles diseases. Long effect of selenium at rats causes pathologic changes on liver. There are not evidences about teratogen effects at monkeys. We don not know too much about poison doses on people, but there are suspicions that selenium is similar to arsenic in physiological reactions. Toxic effects can see on nails, hair and liver. Effects on synthesis of liver proteins are noticed on small group of patients with rheumatic arthritis, with selenium dose of 0, 25 mg Se per day through food. Larger doses can prodice toxic effects, includiong gastrointestinal problems, sniff on garlic, brittle nails, matel taste in mouth and yellowish skin.
Maximal allowable concentrations
According to recommendations of EU (Directive 98/83/EC) and in our rules for drinking water (Sl. list SRJ 42/98) limitary value for selenium is 10 mg/1.