Trace Elements Elements Trace elements in man Trace elements in the earth The essentiality of trace elements The 68 trace elements present in the Earth’s crust each have a concentration of less than 0.1 %, for instance : Fluorine ..................... 700 mg/kg Chlorine .................... 200 mg/kg Chromium ..................200 mg/kg Vanadium ............... .110 mg/kg Nickel ..................... ....80 mg/kg Zinc ............................ 65 mg/kg Nitrogen ..................... 46 mg/kg Copper .................... ...45 mg/kg Cobalt .................... ....23 mg/kg Lead .................... ......15 mg/kg Boron ...................... ....3 mg/kg Molybdenum ............... 1 mg/kg Iodine ...................... ...0.3 mg/kg Cadmium .................... 0.2 mg/kg Selenium .................... 0.09 mg/kg