Selenium is a metal found in natural deposits as ores containing other elements. The greatest use of selenium compounds is in electronic and photocopier components, but they are widely used in other products as well. Selenium releases to the environment have been primarily from copper smelting industries. The largest releases from 1987 to 1993 occurred in Utah. The largest direct releases to water occurred also at that time period in Indiana. The main source of selenium intake for humans is through plant foods in which the plants concentrate the selenium found in soil or taken from groundwater used for irrigation. Selenium (Se) contamination of potable water supplies at concentrations above the current MCL of 0.05 milligram per liter (mg/L) is rare. In a 1982 study AWWA concluded that only 44 water supplies needed to treat for this contaminant.
