Children suffer lasting brain damage from moderate lead poisoning even when they're treated promptly with a drug that removes lead from their blood, according to a large clinical trial reported in the 10 May issue of The New England Journal of Medicine. The results mean that the only way to avert permanent brain damage from lead poisoning is to prevent it in the first place, experts say.
Severe lead poisoning causes brain damage, convulsions, and death, particularly in children. Low to moderate levels of lead, which occur in 1 in 20 children under 6 in the United States, cause subtler damage. Even years after exposure, young children have reduced attention spans and diminished ability to think and reason abstractly. An oral drug called succimer that mops up lead in the blood can save the lives of severely poisoned children. But no one knew whether it could avert brain damage in moderately poisoned children.
To find out, epidemiologist Walter Rogan of the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina, enlisted colleagues at medical centers in four cities that regularly treat lead-poisoned children. The double-blind trial ultimately included 780 2-year-olds, 75% of whom were African American, who had been poisoned, mostly from dust from deteriorating lead paint in their urban homes. The research team removed the lead paint and cleaned the houses. They then gave children either succimer or placebo pills for several months. The children were tested 3 years later, when they were 5--the youngest age at which cognitive deficits can be reliably measured.
Although the drug treatment lowered blood lead values significantly compared to placebo, the treated children showed no differences in IQ, memory, conceptual thinking, or hyperactive behavior from the untreated children. The researchers will test again for differences after the children enter grade school, but so far "there's not even a hint" of a difference, Rogan says.
The paper is "very important because it shows that you can treat kids up the kazoo with a chelating agent and you get nowhere," says pediatrician John Rosen, who runs the Lead Program at the Children's Hospital at Montefiore in Bronx, New York. Together with other studies, the new results underscore the need to remove or replace lead-based paint, which was banned in 1976 in the United States but still coats the walls of 25 million homes. "This is a totally preventable disease and the cure is deleading," Rosen says.
Home page of the Treatment of Lead-exposed Children (TLC) clinical trial
Childhood lead-poisoning prevention program from the Centers for Disease Control and Prevention
Background information on lead poisoning and housing policy from the advocacy group National Center for Lead-Safe Housing