Lead Exposure Damage May Be Permanent, Study Finds : Medicine: Survey is the first to follow affected children to adulthood. It found that learning and behaviorial problems persisted.

Learning and behavioral problems triggered by childhood exposure to lead persist into adulthood, indicating that the damage is permanent, according to a major study published today.

The study, headed by pioneer lead researcher Dr. Herbert Needleman, is the first to follow to adulthood children who were exposed to relatively low levels of lead, most likely from paint, household dust and air pollution. The report comes at a time when researchers are discovering that lead, even at levels widely found in American children and commonly believed to be harmless, impair intellectual ability.

“Exposure to lead, even in children who remain asymptomatic, may have an important and enduring effect on (their) success in life,” Needleman and his colleagues wrote in today’s issue of the New England Journal of Medicine.

The researchers tested 270 first- and second-grade children in the mid-1970s for lead, then compared their performances on a variety of tests. The higher the lead in a child’s system, the worse the youngster performed, the study found. None of the children had any visible symptoms of lead poisoning.

The performance gap was observed again in 1988 when 132 of the research subjects were tested as adults. The others were not available for evaluation. Those with higher lead levels more often failed to graduate from high school and had increased absenteeism, reading disabilities and lower scores on tests measuring vocabulary, grammatical reasoning, fine motor skills and hand-eye coordination.

“Number one, the damage is permanent,” said Needleman, a professor of psychiatry and pediatrics at the University of Pittsburgh. “Number two, it’s very severe. And it’s significant in terms of real-life adaptation.

“If you don’t graduate from high school, you’re in serious trouble as far as making a living is concerned, and if you have a reading disability in addition, you are in very serious trouble.”

The average lead level in the high-lead group of youngsters was 34 micrograms of lead per deciliter of blood, and in the low-lead group, 24 micrograms per deciliter. Those subjects whose blood was retested in 1988 had an average level of only seven micrograms per deciliter, showing that the damage resulted from the childhood exposure and persisted even after the lead levels declined.

The Centers for Disease Control now define lead poisoning as 25 micrograms per deciliter. That guideline is expected to be lowered as a result of several new epidemiological studies that have found evidence of reduced intellectual performance in children whose lead levels are less than half the federal standard.

Since Needleman’s initial study, lead levels in the general population have fallen significantly, primarily because of the phase-out of leaded gasoline in the early 1970s. But federal health authorities estimate that between 3 million and 4 million American children still have potentially hazardous levels of lead in their blood.

Adults can be poisoned by lead, but children are more vulnerable because they are undergoing rapid neurological and physical development and are prone to put dust-covered objects, including their hands, in their mouths.

Youngsters are primarily exposed to lead from old paint that is peeling or chalking and contaminating household dust. They also can be exposed through automobile exhaust and industrial emissions in the air and soil or from water contaminated by lead pipes or lead solder. Improperly glazed dishes are yet another source of lead poisoning.