In workers who are exposed to iron fume, iron oxide particles may become deposited in the lungs. If these deposits are present in sufficient number, they become visible on X-rays of the lungs as fine nodular opacities, and this condition is known as siderosis.
Pure siderosis, associated with exposure to iron alone, is a benign condition. There is no fibrosis, and no effect on the function of the lungs. When exposure ceases, the opacities disappear.
Welders are sometimes found to have siderosis. While pure iron does not appear to have any harmful effects, welding fume may contain many other constituents. Therefore welders displaying the signs of siderosis may sometimes also display other symptoms which reflect the combined effects of exposure to irritant gases and fumes.