In high concentrations, selenium acts as an environmental contaminate. Sources of pollution include waste materials from certain mining, agricultural, petrochemical, and industrial manufacturing operations. In Belews Lake North Carolina, 19 species of fish were eliminated from the lake due to 150-200 ug Se/L wastewater discharged from 1974 to 1986 from a coal-fired power plant. At the Kesterson National Wildlife Refuge in California, thousands of fish and waterbirds were poisoned by selenium in agricultural irrigation drainage.