If a child gets lead poisoning, how long does it take for his system to clear after no longer getting exposed?

Months. Once absorbed, 90% is stored in bond as lead phosphate. The other 10% is taken up by the red blood cells, the brain, the kidneys, and the liver, where toxic effects can develop. To excrete lead: 90% put out in stool; 9% in urine; it takes twice as long to excrete lead as to absorb it. The one-half life of lead in body is 2 months. So the level will decrease by 1/2 every 2 months.