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http://content.nejm.org/cgi/content/abstract/348/16/1517
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Intellectual Impairment in
Children with Blood Lead Concentrations below 10 µg per Deciliter
Richard L. Canfield, Ph.D., Charles R. Henderson, Jr., M.A., Deborah A. Cory-Slechta, Ph.D., Christopher Cox, Ph.D., Todd A. Jusko, B.S., and Bruce P. Lanphear, M.D., M.P.H.
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ABSTRACT
Background Despite dramatic declines in children's blood lead concentrations and a lowering of the Centers for Disease Control and Prevention's level of concern to 10 µg per deciliter (0.483 µmol per liter), little is known about children's neurobehavioral functioning at lead concentrations below this level.
Methods We measured blood lead concentrations in 172 children at 6, 12, 18, 24, 36, 48, and 60 months of age and administered the Stanford–Binet Intelligence Scale at the ages of 3 and 5 years. The relation between IQ and blood lead concentration was estimated with the use of linear and nonlinear mixed models, with adjustment for maternal IQ, quality of the home environment, and other potential confounders.
Results The blood lead concentration was inversely and significantly associated with IQ. In the linear model, each increase of 10 µg per deciliter in the lifetime average blood lead concentration was associated with a 4.6-point decrease in IQ (P=0.004), whereas for the subsample of 101 children whose maximal lead concentrations remained below 10 µg per deciliter, the change in IQ associated with a given change in lead concentration was greater. When estimated in a nonlinear model with the full sample, IQ declined by 7.4 points as lifetime average blood lead concentrations increased from 1 to 10 µg per deciliter.
Conclusions Blood lead concentrations, even those below 10 µg per deciliter, are inversely associated with children's IQ scores at three and five years of age, and associated declines in IQ are greater at these concentrations than at higher concentrations. These findings suggest that more U.S. children may be adversely affected by environmental lead than previously estimated.
Source Information
From the Division of Nutritional Sciences (R.L.C.) and the Department of Human Development (C.R.H.), College of Human Ecology, Cornell University, Ithaca, N.Y.; the Departments of Environmental Medicine (D.A.C.-S.) and Biostatistics and Computational Biology (C.C.), University of Rochester School of Medicine, Rochester, N.Y.; the Division of Epidemiology, Statistics, and Prevention, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, Md. (C.C.); the Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle (T.A.J.); and Cincinnati Children's Environmental Health Center, Children's Hospital Medical Center, Cincinnati (B.P.L.).
Address reprint requests to Dr. Canfield at the Division of Nutritional Sciences, College of Human Ecology, Cornell University, Ithaca, NY 14853, or at rlc5@cornell.edu.
This article has been cited by other articles:
(2003). Lead: Devastating
Effects, Even at Low Levels of Exposure. Journal Watch (General)
2003: 4-4
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