Nickel is poorly absorbed by the body. Less than 10% is absorbed in the gastrointestinal tract. The seven known nickel enzymes are urease, hydrogenase, CO-dehydrogenase, methyl-coenzyme M reductase, Ni-superoxide dismutase, glyoxalase I and cis-trans isomerase. When nickel enters the body it is distributed to all organs, but mostly in the kidney, bone, and the thyroid gland where it can exerts its toxicity. If nickel enters the body with nickel-contaminated air it is retained in the lungs. Nickel, which enters the blood stream is excreted in the urine, and if it is entered by the food it is excreted in the feces.