Selenium is a very rare element with abundance estimated at about 0.05 to 0.09 parts per million, and the 25th least common elements in the Earth's crust. It widely spreads throughout the crust.
The elemental state of selenium does not or very rarely exists in the nature. There is no natural ore specially for mining and commercial refinery of selenium. Pyrite and related sulfide cores contain minor selenium that partially replaces sulfur. Commercial selenium elemental product is essentially obtained as a side-product in the refinery of other elements. Copper, iron and lead ores are very commonly used as commercial production of selenium. Japan, Canada, Belgium, the United States, and Germany are the major producers of selenium.
Selenium physical properties
Selenium comes up in a number of allotropic forms: The most acknowledged are a red amorphous powder, a red crystalline material, and a gray crystalline metal-like form called metallic selenium. This last form flows electricity better in the light than in the dark and is employed in photocells. The melting point of selenium crystal is 217°C (423°F ) and its boiling point is 685°C (1,260°F). It has a density of 4.5 grams per cubic centimeter.
Elemental selenium is a semiconductor, a substance that conducts an electric current better than non-conductors, but not as well as conductors. It is widely used today in the electronics industry for the manufacture of transistors for computers, cellular phones, hand-held electronic games. It is a key element for copying machines due to its special electronic properties. Selenium is also used in the metal alloy and in the glass-making industry for special color properties of the glass.
Selenium chemical properties
Selenium reacts easily with hydrogen, fluorine, chlorine, and bromine. It combines with some metal ions to form compounds called selenide salts such as calcium selenide (CaSe). It burns in air via oxidation to give a bright blue flame to form selenium dioxide (SeO2) that has a characteristic odor of rotten horseradish:
Se + O2 → SeO2
SeO2 molecules dissolve in water, resulting in selenous acid, H2SeO3.
Selenium does not react with water, but dissolves in concentrated nitric acid and alkalis. Selenous acid can also be made directly by oxidizing elemental selenium with nitric acid: 3 Se + 4 HNO3 → 3 H2SeO3 + 4 NO
The oxidation of selenium dioxide with hydrogen peroxide produces selenic acid, H2SeO4:
SeO2 + H2O2 → H2SeO4
Dehydration of selenic acid H2SeO4 generates selenium trioxide (SeO3), which is also a stable compound at room temperature and decomposes to the dioxide above 185 °C:
2 SeO3 → 2 SeO2 + O2 (ΔH = −54 kJ/mol)
Selenous acid, H2SeO3 combines with metal ions to selenite salts, such as silver selenite (Ag2SeO3) and sodium selenite (Na2SeO3).
Selenous acid, H2SeO3 reacts with hydrogen sulfide to produce selenium disulfide:
H2SeO3 + 2 H2S → SeS2 + 3 H2O
Some commercial shampoo products contain selenium disulfide as an anti-dandruff agent. Other uses of selenium disulfide include a polymerization inhibitor in polymer chemistry, a glass-coloring agent, and a reducing agent in fireworks.
Concentrated selenic acid is strong enough in dissolving gold under heated conditions to form gold(III) selenate.
Antioxidant properties and health benefits of Selenium
Selenium as an antioxidant is an indispensable trace mineral playing very vital roles in ensuring good health conditions, especially in the kidneys, liver, pancreas, spleen and the lymph nodes to carry out vast gamut of bodily movements and functions. Several bodily functions like reproduction, thyroid activity, DNA synthesis, correct eye functioning, muscle function and the efficient working of the heart, are carried out by Selenoproteins.
Selenium is very much required and unavoidable from viewpoint of ensuring smooth ongoing functions of Thyroid Hormones, which conduct several most important activities in our body including boosting up of body metabolism, making the cardiovascular system more responsive to sensitive nervous activity, boosting up of heart muscle contractions, increasing the formation of red blood cells, increasing other endocrine tissues activities and also making sure proper skeletal growth in children.
Selenium is a prerequisite for men to keep themselves sexually fit as selenium is important in that it conducts a number of beneficial activities in men including generations of sperms which is very vital to maintain reproductive capacity in men. Men, lacking in Selenium are at greater risk of developing infertility, that is, they might find it difficult to carry out reproductions-a required process to ensure generation running and to promenade a child.
Selenium is an important element of glutathione peroxidase (GPx, or so called "Master Antioxidant"). Glutathione peroxidase is the most profuse water-soluble antioxidant in the body that incorporates lipoid acid, CoQ-10, and vitamins C and E. A ceaseless circulation of Glutathione all across the body is important all the time to ensure keeping immune cells refreshed. Glutathione peroxidase containing selenium plays a role in expelling contaminated waste products out of your body apart from stocking up other elements of the antioxidant network viz. lipoic acid, CoQ-10, vitamins C and E when they are exhausted. It also plays a very important role in maintaining your cell membranes strong and enhancement of vital amino acids into the cells.
The higher the levels of glutathione raised up in your body, stronger resistance to chronic diseases is put forth by your body. A range of ills like inflammation, autoimmune diseases, asthma, chronic fatigue and many more can be kept at bay with its help.
Selenium and vitamin E work in tandem in supplement of antioxidant and immuno stimulating functions which are essential to stop the fast body ageing on account of tissue oxidation.
Selenium and AIDS:
People preyed upon by deadly disease like AIDS are often reported to be undersupplied in glutathione which again can lead to extreme oxidative stress conditions, which in addition to deteriorating the bodily immune mechanism, expedites aging. It has been revealed in several studies that most glaring underlying cause behind aging is oxidative stress caused by free radical attacks. AIDS patients lacking in required levels of glutathione are at heightened risk of dying. Thus by enhancements in selenium, accompanied with alpha-lipoic acid and the amino acid N-acetyl-cysteine the level of glutathione can be upheld.
Selenium and cancer:
Selenium also offers protections from several sorts of cancers, including lung, prostate and colon cancer. Many studies conducted so far have made it evident and verified fact that selenium has good degree of powerful capability to expedite the obliteration of tumor cells.
The antioxidant network works in harmony as the belief held most generally about the antioxidant network, it is improbable that selenium all by itself can reduce the rate of cancer. Supplement of Selenium is essential for the productions of glutathione that by conducting recycling of vitamin C and vitamin E, gives the maximum protections against cancers.
Selenium and healthy blood sugar levels:
Selenium is believed to emulate the functions of insulin. In several examinations conducted in labs it has been demonstrated that Seleniums are capable of carrying out number of functions which otherwise would be deemed to be made by insulin like stimulating glucose uptake and regulating metabolic processes including glycolysis, gluconeogenesis, fatty acid synthesis and the pentose phosphate pathway. However the precise system of the insulin emulating functions of selenium has as yet to be explicated, it is believed that these functions are carried out by activation of key proteins involved in the insulin-signal cascade. Selenium is also believed to be playing the most decisive roles in lessening the oxidative stress attached with diabetes, thereby blocking the development of the resulting ailments of diabetes such as neuropathy, retinopathy and cataracts.
Selenium and arthritis:
Deficiency in selenium levels has been linked with the occurrence of arthritis. Groundwork studies point to the helpful role of selenium as a free fundamental scavenger that has the potential to hold up the development of arthritis. For people having high levels of oxidative stress, selenium proves to be a bless in that it places important roles as an antioxidant benefiting to the health in numerous ways. People like smokers, those preyed upon by inflammatory diseases like rheumatoid arthritis or those people who are victimized by infections which can imperil their cell immunity.
Thus overall, the chief role of selenium in the human body is to act protectively as an antioxidant, safeguarding our body from oxygen related damage, keeping certain types of cancer, heart disease, joint inflammation and arthritis at bay.
This nutrient has also been connected with powerfully dawdling the development of the human immunodeficiency virus (HIV).
Meat, grains, fish and dairy products Nuts, fish, Brazil nuts, mixed nuts, salmon, and shrimp are all considered to rich sources of selenium. Nonetheless, the largest part of our foods has very low quantities. The cause for its scanty availability in our daily diets can be traced in the fact that it is a trace mineral extracted from plants which absorb them from soil. This indicates that for the most part it is fundamentally reliant on soil conditions.
Soils that are lacking in selenium comprise those in volcanic regions, soils with high iron, acid soils and those with aluminum content. There are regions of Europe, China, and New Zealand recognized for having selenium-lacking soils. Doctors are actually becoming worried about retreating selenium in these regions of the globe.
Soils deficient in selenium are more likely to witness higher rates of cancer as compared to those areas where soil is richly supplied in selenium.
Possible side effects
On making too much consumption more than required and prescribed quantity selenium can trigger of following Side effects: garlic odor in breath, lung problems, breathlessness gastrointestinal irritation, stomach upsets, nausea, vomiting, diarrhea, stomach pain, fatigue, muscle cramps, restlessness, listlessness, dementia, behavioral problems, metallic taste in the mouth, hair loss, skin inflammation, tooth decay, and fingernail discoloration, damage to nervous system, impairment of liver, impairment of kidney, thyroid malfunction, jaundice, dermatitis, birth defects, and stunting of growth. In extreme cases fever and damage to lung and heart might also happen resulting ultimately mortality.
Relief, treatment and cure from selenium side effects
Treating selenosis starts with doing away with the causative factor. The patient is made to drink adequate water to wash down the surplus dropping side effects. There is no remedy for this mineral. In severe overdose cases hospitalization becomes required for the restoration of the patient and for the treatment.
SELENIUM DEFICIENCY AND SYMPTOMS
The symptoms of deficiency are as follows:
Kashin-Beck disease (a bone and joint disorder), Keshan disease (a heart disorder), myxedematous endemic cretinism (a disease that causes mental retardation) and osteoarthritis (the chronic breakdown of cartilage in the joints).
The Recommended Dietary Allowance (RDA) controls the lowest required ingestion of selenium. The RDA for vitamins may be used as targets for each person. Quantity of vitamins to be consumed differs from person to person in accordance to his or her your age and gender. Other factors, such as pregnancy and illnesses, are also considerable when determining the dosage of selenium to be consumed. Women during pregnancy and or those having babies to breast feed need higher amounts selenium.
Dietary Reference Intakes for selenium
Tolerable Upper Intake Levels for Infants, Children, and Adults:
Age Males and Females (μg/day) 0 - 6 months 45 7 - 12 months 60 1-3 years 90 4-8 years 150 9-13 years 280 14-18 years 400 19 years + 400
The best way to supplement the every day necessity of indispensable vitamins is to consume a fair diet that including a array of foods.
Selenium sulfide (approximate formula SeS2) is the lively component in some anti-dandruff shampoos. The selenium compound destroys the scalp fungus Malassezia, which results in shedding of dry skin fragments. The component is also employed in body lotions to treat Tinea versicolor on account of being infected by a diverse species of Malassezia fungus.
Selenium is employed extensively in vitamin making up and other dietary supplements, in small doses (typically 50 to 200 micrograms per day for adult humans). Some livestock feeds are prepared with selenium as well.
Detection in biological fluids
Selenium may be calculated in blood, plasma, serum or urine to check extreme ecological or occupational contact, to verify a analysis of toxicity in hospitalized victims or to aid in a forensic examination in a case of deadly over dosage.
Selenium as an antioxidant is a required trace mineral and is highly conducive in maintenance of good health conditions related to the kidneys, liver, pancreas, spleen and the lymph nodes for executing mammoth extent of physical activities and functions. In addition, a wide variety of mortal illnesses like aids, cancer etc can be evaded in the human body.