Studies have shown that people exposed to uranium may develop lung cancer, leukaemia, chromosomal aberrations, fibrosis of the lungs and non-malignant respiratory diseases. After entering the bloodstream, the absorbed uranium tends to accumulate and stay for many years in bone tissue because of uranium's affinity for phosphates. The greatest health risk from large intake of uranium is toxic damage to kidneys, because besides being weakly radioactive, uranium is a toxic metal. Finely divided uranium metal presents a fire hazard because uranium is pyrophoric, meaning small grains can ignite spontaneously in air at room temperature.