Chromium is an essential trace element for humans and other living beings. However, high concentrations of Chromium are toxic. Chromium has three valence states, divalent chromium, trivalent chromium and hexavalent chromium. Its toxicity is related to its valence states. Trivalent chromium is essential for the human body for carbohydrate metabolism. However, hexavalent chromium is extremely toxic to humans. It could make our skin rough and do damage to the liver. It is also carcinogenic and will accumulate in the human body. The chromium content in natural bodies of water is low and it is even lower in seawater.