ABSTRACT
References 177
potential toxicities; however, there are trace elements known to have toxic effects that are also essential dietary nutrients. Several of these elements have specific deficiency symptoms and can lead to death of the organism. These same essential elements are toxic when an organism has an increased intake, whether by dietary means or other exposure routes. Trace metals such as copper, zinc, iron, and selenium are known for their deficiencies. With respect to selenium, early work focused on its toxicity, especially in the livestock industry where selenosis in specific regions of the world is likely to occur due to the naturally high selenium content of the soil. On the other hand, copper, zinc, and iron have been primarily evaluated in regard to deficiency aspects. Toxicity due to these minerals is known to occur via industrial and environmental exposures. Also, due to the propensity of many individuals to consume nutrient supplements, toxicity symptoms and specific levels known to lead to these symptoms have been of increased interest.13
