1. Shijiazhuang Subsidiary of China Science Publishing & Media Ltd., Shijiazhuang 050030, China;
2. Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
Abstract Selenium (Se) as an element of Group ⅥA has the properties of non-metallic, as well as some metallic characters. Se is widely spread but unevenly distributed in the natural environment, and the content of Se in earth's crust ranges 0.05~0.09 mg/kg. As an essential trace element for animals and human beings, Se has important physiological and biochemical functions. However, excess Se and its compounds are highly toxic, and the range between toxicity and essentiality is quite narrow. This paper briefly introduces the natural existence of Se in the environment, the biological effect of Se as well as its molecular basis with the aim of commemorating the 150th anniversary of the discovery of periodic law of elements.
