微量元素是指那些在人的体重中含量在百万分之五十以下的元素。这些元素可分为3类:一类是世界公认(1973年世界卫生组织公布)的人体必需的微量元素有14种,即铁、锌、硒、锰、铜、碘、钼、钴、铬、氟、硅、钒、镍、锡等;另一类为生理功能尚不十分明确,或未予定论的,如锶、砷、铍、锗等。第三类则是对人体有害的如汞、铅、镉等。与微量元素相对应的是常量元素,它们是指在人的体重中含量在百万 Trace elements are those that contain less than 50 parts per million of a person’s body weight. These elements can be divided into three categories: one is the world’s recognized (1973 World Health Organization announced) the human body has 14 kinds of trace elements, namely iron, zinc, selenium, manganese, copper, iodine, molybdenum, cobalt, chromium, Fluoride, silicon, vanadium, nickel, tin, etc .; the other is not yet very clear physiological function, or not conclusive, such as strontium, arsenic, beryllium, germanium and so on. The third category is harmful to the human body, such as mercury, lead, cadmium and so on. Corresponding to the trace elements are the elements of the constant, they are in the human body weight in millions