Even A Bit of Lead Is Bad For Kids' Psychological Development

Superman couldn't see through lead, but doctors and psychologists did, exposing lead's damaging effects on children's psychological development.

Findings

Lead is hiding all around us — in house paint, in car exhaust, even in water pipes and food cans. As a result, lead is also in our blood and bones. In the 1970s, experts thought that children who had less than 30 micrograms of lead per deciliter of blood (30mcg/dl) were safe from its effects. However, a research team headed by pediatrician Herbert Needleman, MD, and later joined by psychologist David Bellinger, PhD, exposed how dangerous even a little lead exposure can be. Needleman and his team first tested how much lead was in the baby teeth of 2,335 first and second graders with no symptoms of lead poisoning. The researchers then had the 58 children with the highest lead levels and the 100 with the lowest lead levels complete a series of tests, and had teachers rate the children's behavior. The researchers found that the high-lead children had lower IQs, less verbal competence, worse speech processing, and worse attention than did the low-lead children.

Lead also affected the children's behavior: teachers consistently judged the high-lead children to have more difficulty following directions, to be more hyperactive, and to have lower overall functioning than the low-lead children. According to the federal guidelines at the time of this study (1979), children in both the high- and low-lead groups had relatively low levels of lead in their blood. Needleman's and colleagues' results clearly showed that even relatively small amounts of lead were associated with significant cognitive and behavioral problems. These researchers have also demonstrated that children from both impoverished and affluent backgrounds suffer from high lead exposure, underscoring how widespread the problem is.

Significance

Needleman's study was among the first to raise public awareness about the effects of environmental pollutants on children's psychological development. Before this study and the ensuing body of research that it inspired, environmental influences on intelligence and behavior were under-appreciated. These researchers showed that even small amounts of a common metal like lead have strong effects on children's intelligence and personality.

This body of research also ushered in an emphasis on "behavioral toxicity," not just "somatic toxicity." Researchers had previously focused almost exclusively on pollutants' relationships to diseases such as cancer. Needleman's team showed that pollutants often affect children's behavior and cognitive functioning long before disease develops. By using psychological measures of toxicity, researchers may be able to slow, stop or even reverse the progress of disease.

Practical Application

In 1992, Congress passed the Residential Lead-Based Paint Hazard Reduction Act (Title X), which sought to control lead-based paint hazards in housing where young children reside. Leaded gasoline was also phased out between 1973 and 1995.

Experts have also continued to revise their recommendations for safe lead levels as a result of numerous studies linking lead exposure to behavioral and attention problems, poor academic achievement, and juvenile delinquency. In 2012, the Centers for Disease Control and Prevention (CDC) lowered the "blood level of concern" for lead from 10 mcg/dL to 5 mcg/dL. The CDC, Department of Housing and Urban Development, U.S. Environmental Protection Agency and other agencies have developed a federal strategy to eliminate childhood lead poisoning by 2020.

Avoiding lead exposure is the best way to keep lead levels in check. The CDC advises parents to test paint and dust in homes built before 1978. Renovation activities such as sanding and demolition, which can create hazardous lead dust, should be performed by certified renovators who are trained to follow practices approved by the EPA.

Cited Research

Needleman, H. L., Gunnoe, C., Leviton, A., Reed, R., Peresie, H., Maher, C., & Barrett, P. (1979). Deficits in psychologic and classroom performance of children with elevated dentine lead levels.  The New England Journal of Medicine, 300,  689-695.

Additional Sources

Bellinger, D., Leviton, A., Waternaux, C., Needleman, H., & Rabinowitz, M. (1987). Longitudinal analyses of prenatal and postnatal lead exposure and early cognitive development. The New England Journal of Medicine, 316,  1037-1042.

Needleman, H. L., & Gatsonis, C. A. (1990). Low-level lead exposure and the IQ of children. A meta-analysis of modern studies. Journal of the American Medical Association, 263, 673-678.

Needleman, H. L., Riess, J. A., Tobin, M. J., Biesecker, G. E., & Greenhouse, J. B. (1996). Bone lead levels and delinquent behavior. Journal of the American Medical Association, 275,  363-369.

Centers for Disease Control and Prevention - Blood Lead Levels in Children Fact Sheet (PDF, 292KB)

Centers for Disease Control and Prevention — Lead

Children's Environmental Health Initiative

Environmental Protection Agency-Office of Children's Health Protection-Concentrations of Lead in Blood


American Psychological Association, February 2014