The evolution of the radiologic lead line.

Serial radiographs of lead-poisoned children showed separation of lead lines from the zone of provisional calcification within four weeks at sites of rapid growth. Lead lines do not appear until blood lead attains a concentration of 70 to 80 micrograms/dl. They are not affected by treatment, but disappear spontaneously within four years. While they remain in the diaphysis, they provide a marker for the time of onset of lead toxicity and the subsequent rate of bone growth.