The water crisis in Flint, Mich., highlights the toxicity of lead. While the most publicized consequence of lead exposure are the long-term effects on developing brains, this toxic metal also damages the kidneys of adults and children. The people of Flint face a number of long-term health risks related to their current lead exposure, including chronic kidney disease. Adults in the area, especially those already facing kidney problems, may suffer acceleration of their health issues.
Lead reduces the kidneys’ ability to work properly, causing the kidneys to raise blood pressure, leak protein and eventually stop working altogether. Although the effects on the kidneys are well-known, how lead damaged the kidneys wasn’t clear until recently when a study in Environmental Health Perspectives revealed that the damage was actually done through another metal, iron.
Iron is found in red blood cells (RBCs) and allows RBCs to carry oxygen to the body. Normally, old or damaged RBCs are cleared out of circulation by the liver and spleen. Cells in these organs engulf or “eat” damaged RBCs and recycle them into new RBCs. Lead poisoning damages so many RBCs that the kidneys start clearing them, too. Scientists from Seoul National University in South Korea found that as the consumed RBCs broke down inside the kidney cells, iron got left behind.
The scientists first showed that kidney cells exposed to RBCs from people with lead poisoning did not grow as well as cells that weren’t exposed to lead-damaged RBCs. Exposing kidney cells to lead alone, though, did not harm them. When damaged RBCs were around, the kidney cells engulfed them, and the ingested RBCs deposited iron within the cells. Iron is a well-known toxin to kidney cells, so it appeared that the iron left by the lead-damaged RBCs, not lead itself, caused the kidney cells to die.
The scientists then examined rats that drank water with lead for 12 weeks. As expected, kidneys from the lead-exposed rats showed damage. The damaged kidney areas had iron deposits, further supporting that injured RBCs and the iron they left behind contributed to the scarring in the kidneys.
Currently, we have no way to clear iron from the kidneys. Further studies may produce new treatments for kidney damage from lead exposure. Of course, the best treatment is to get the lead out.
Pascale Lane, MD, is a pediatric nephrologist and professor at the Oklahoma University Health Sciences Center.