Even A Bit of Lead Is Bad For Kids' Psychological Development
Lead is everywhere-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 1970's, 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 and later joined by psychologist David Bellinger exposed how dangerous even a little lead exposure can be. Dr. Needleman and his team first tested how much lead was in the baby teeth of 2335 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 IQ's, 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 did 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. Dr. Needleman and colleagues' results clearly showed that the high-lead children experienced 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.
Needleman's study was among the first to raise public awareness about the effects of environmental pollutants on children's psychological development. Prior to 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 like cancer. Needleman's team showed that pollutants often affect children's behavior and cognitive functioning long before disease develops. By using these psychological measures, researchers may be able to slow, stop, or even reverse the progress of disease.
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.
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.
American Psychological Association, July 9, 2003