chromium (Cr) /krō″mē·əm/ [Gk, chroma, color] , a hard, brittle metallic element. Its atomic number is 24; its atomic mass is 51.99. It does not occur naturally in pure form but exists in combination with iron and oxygen in chromite, a mineral found chiefly in Africa, Albania, Russia, and Turkey. Chromium strongly resists corrosion and is used extensively to plate other metals, harden steel, and, in combination with other elements, form colored compounds. Stainless steels are more than 10% chromium and strongly resist rusting. Traces of chromium occur in plants and animals, and there is evidence that this element may be important in human nutrition, especially in carbohydrate metabolism. Some experts estimate that the safe and adequate daily intake of chromium ranges from 0.1 to 0.2 mg, depending on the age of the individual. Workers in chromite mines are susceptible to pneumoconiosis caused by the inhalation of chromite dust particles that lodge in the lung. Chromate salts have been identified as potential carcinogens. Chromium 51 isotope is used in blood studies.
