Introduction. The long-term intake of excessive selenium may involve either organic or inorganic forms in food or water. UPDATE STATEMENT . Selenium is a trace element that is naturally present in many foods, added to others, and available as a dietary supplement. Toxicological profiles are revised and republished as necessary, but no less than once every three years. Selenium is an essential nutrient that is incorporated into functional and structural proteins as selenocysteine. Chronic selenium poisoning usually develops when livestock consume seleniferous forages and grains containing 5–50 ppm of selenium for many weeks or months, although chronic exposure to high concentrations of inorganic selenium can also produce chronic selenosis.
Selenium, which is nutritionally essential for humans, is a constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection [].
Selenium is an essential element that has a narrow margin of safety, with the difference between adequate and potentially toxic concentrations in the diet being approximately 10- to 20-fold. SELENIUM iii .
Selenium toxicity causes the hair to become brittle, hair loss, deformed and brittle nails, sloughing off of the nails, discoloration of the teeth, tooth decay and discolored skin. Several of these proteins are enzymes that provide cellular antioxidant protection. This edition supersedes any previously released draft or final profile. The poisonous nature of many selenium compounds remained more or less a laboratory curiosity until the 1930s, when it was discovered that selenium was the active principle in forages and grains that caused alkali disease in livestock raised in certain areas of the American great plains. A Toxicological Profile for selenium, Draft for Public Comment was released in September, 2001.