Teens' kidney function harmed by even low lead levels

Blood levels of lead below those considered elevated by the Centers for Disease Control and Prevention still may negatively impact kidney function in otherwise healthy adolescents, says a study in the Jan. 11 Archives of Internal Medicine.

Researchers at the Johns Hopkins Children's Center in Baltimore gathered data from 769 adolescents, ages 12 to 20, who participated in the Third National Health and Nutrition Examination Survey from 1988 to 1994.

Nearly all of the participants had blood lead levels below 10 ug/dl (the CDC's threshold for concern), with an average level of 1.5 ug/dl.

Researchers found that higher lead levels, which were still below 10 ug/dl of blood, were consistently associated with a lower glomerular filtration rate.

"There is a lot of accumulating evidence showing a role of lead [in kidney disease]. ... But I was a little surprised that we saw the association in a relatively small population of healthy kids," said Jeffrey Fadrowski, MD, a pediatric nephrologist and assistant professor of pediatrics at the Johns Hopkins University School of Medicine in Baltimore and an author of the study (link).

Adolescents with blood lead levels of 3 ug/dl or greater had lower glomerular filtration rates than those with lead levels that were less than 1 ug/dl of blood. For each twofold increase in the amount of lead in the blood, the kidney's filtration capacity dropped by 2.3 units in males and 3.3 units in females.

The link between higher lead levels and decreased kidney function persisted even after researchers eliminated hypertension, which less than 5% of study participants had, as a possible factor affecting kidney status.

The CDC recognizes that adverse effects exist at blood levels less than 10 ug/dl, but such levels cannot clinically be characterized as lead poisoning, said Mary Jean Brown, chief of the CDC's Healthy Homes and Lead Poisoning Prevention branch.

Dr. Fadrowski said more studies are needed to examine the possible impact of environmental lead exposure on kidney function. Brown said more needs to be done to eliminate lead in children's environments before they are exposed.

"And we're moving in that direction," Brown said, citing legislation approved in 2009 that reduced the permissible total lead content in children's products, and the Clean Air Act, which has lowered lead concentrations in the air.