In fish and other wildlife, selenium is necessary for life, but toxic in high doses. For salmon, the optimal concentration of selenium is about 1 microgram selenium per gram of whole body weight. Much below that level, young salmon die from deficiency; much above, they die from toxic excess.The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for selenium in the workplace at 0.2 mg/m3 over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 0.2 mg/m3 over an 8-hour workday. At levels of 1 mg/m3, selenium is immediately dangerous to life and health. Deficiency
Selenium deficiency can occur in patients with severely compromised intestinal function, those undergoing total parenteral nutrition, and in those of advanced age (over 90). Also, people dependent on food grown from selenium-deficient soil are at risk. Although New Zealand soil has low levels of selenium, adverse health effects have not been detected in the residents.Selenium deficiency, defined by low (<60% of normal) selenoenzyme activity levels in brain and endocrine tissues, occurs only when a low selenium level is linked with an additional stress, such as high exposures to mercury or increased oxidant stress from vitamin E deficiency.Selenium interacts with other nutrients, such as iodine and vitamin E. The effect of selenium deficiency on health remains uncertain, particularly in relation to Kashin-Beck disease. Also, selenium interacts with other minerals, such as zinc and copper.
Alloys
Selenium is used with bismuth in brasses to replace more toxic lead. The regulation of lead in drinking water applications such as in the US with the Safe Drinking Water Act of 1974, made a reduction of lead in brass necessary. The new brass is marketed under the name EnviroBrass. Like lead and sulfur, selenium improves the machinability of steel at concentrations around 0.15%. Selenium produces the same machinability improvement in copper alloys. Lithium–selenium batteries
The lithium–selenium (Li–Se) battery is one of the most promising systems for energy storage in the family of lithium batteries. The Li–Se battery is an alternative to the lithium–sulfur battery, with an advantage of high electrical conductivity. Solar cells
Selenium was the basis of the very first solar cells, with the first example of rooftop solar being a selenium cell from 1884. Such cells were later used in battery-free light meters for photography. Copper indium gallium selenide is a material used in solar cells. Photoconductors
Amorphous selenium (α-Se) thin films have found application as photoconductors in flat panel x-ray detectors. These detectors use amorphous selenium to capture and convert incident x-ray photons directly into electric charge. Rectifiers
Selenium rectifiers were first used in 1933. Their use continued into the 1990s. Other uses
Small amounts of organoselenium compounds have been used to modify the catalysts used for the vulcanization for the production of rubber.The demand for selenium by the electronics industry is declining. Its photovoltaic and photoconductive properties are still useful in photocopying, photocells, light meters and solar cells.