Chromium is a substance that has many uses. It is an essential element in our bodies in one form that can help regulate blood sugar. In another form, it is a potentially dangerous chemical used in metal plating. Zinc chromium can be one of the least of the dangerous types because it is usually in the form of trivalent chromium. Hexavalent chromium has been used in some metal plating on vehicles and the industry is changing that to the safer form of the element, particularly in Europe. The concern among environmental and health officials is over the dangers to people from hexavalent chromium exposure. The substance is a known carcinogen. Studies show that workers exposed to it have higher incidents for lung cancer and other respiratory problems. Chromium pollution in water ways can cause cancer among nearby residents who use the water supply, as was shown in the movie "Erin Brokovich."