Chromium in nature mainly in the trivalent form of chromium and hexavalent chromium. Hexavalent chromium is mainly harm for people with chronic poisoning, which can be through the digestive tract, respiratory tract, skin and mucous membrane into the human body. The body accumulates mainly in liver, kidney and endocrine glands in the. Through the respiratory tract is easy to accumulate in the lungs. Hexavalent chromium has a strong oxidation, so the chronic poisoning often began with the development of local damage to the hopeless. Invade the body through the respiratory tract, the start against the upper respiratory tract, causing rhinitis, pharyngitis and laryngitis, bronchitis.