Subclinical Lead Level and Developmental Deficit: Re-Analyses of Data

Abstract

Perino and Ernhart (1974) reported that moderate levels of lead exposure in 80 preschool urban black children were related to cognitive impairment. Ernhart, Landa, and Schell (1981) re-examined 63 of these children five years later and found no significant association of preschool lead level and outcome measures—including cognitive measures, reading tests, and teacher behavior ratings. School-age lead level was marginally related to a few measures. After review of methodological issues, it was concluded that if these results were due to lead, the effect was minimal. Since the issue is important to the task of the Environmental Protection Agency (EPA), EPA appointed an Expert Committee to examine these reports and those of another person whose work has been questioned. Some data re-analyses were requested.

The previously reported positive findings of the preschool study were not substantiated in re-analysis. The school-age lead data required technical adjustment. Additional variables were generated including change scores, combinations, and interactions. Out of 66 analyses, two tests of the lead effect were significant. The first depended on a deviant case; the second was an uninterpretable interaction. It was concluded that if these results are due to a lead effect, the effect is minimal. The most important result was unchanged; there was no evidence of an effect of moderate blood lead levels in the preschool period and any school-age outcome measure.

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References

Ammons, R. B. & Ammons, C.H. The Quick Test (QT): Provisional Manual. Psychological Reports, 1962; 11:111.

Annest, J.L. , Pirkle, J.L. , Makuc, D. , Neese, J.W. , Bayse, D.D. , & Kovar, M.G. . Chronological trend in blood lead levels between 1976 and 1980. New England Journal of Medicine 1983, 308, 1373–1377.

Boone, D.J. , Hearn, T. , & Lewis, S. . Comparison of interlaboratory results for blood lead with results from a definitive method. Clinial Chemistry 1979, 25, 389–393.

Carter, G. F. . The paper punched disc technique for lead in blood samples with abnormal haemoglobin values. British Journal of Industrial Medicine 1978, 35, 235–240.

Center for Disease Control. Preventing lead poisoning in young children. Journal of Pediatrics, 1978, 93, 709–720.

Cohen, J. & Cohen, P. Applied Multiple Regression/Correlation Analysis for the Behavioral Sciences. Second Edition. Hillsdale, NJ: Lawrence Erlbaum Associates, 1983.

Conners, C.K. A teacher rating scale for use in drug studies with children. American Journal of Psychiatry, 1969, 126, 884.

Ernhart, C.B. , Landa, B. , & Schell, N.B. . Subclinical levels of lead and developmental deficit: A multivariate follow-up reassessment. Pediatrics 1981, 67, 911–919.

Kleinbaum, D.G. , Kuper, L.L. , & Morgenstern, H. Epidemiologic Research. Belmont, CA: Lifetime Learning, 1982.

10.

Koppitz, E.M. The Bender Gestalt Test for Young Children. New York: Grune & Stratton, 1963.

11.

Mahaffey, K.R. , Annest, J.L. , Roberts, J. , & Murphy, R.S. National estimates of blood lead levels: United States, 1976–1980. New England Journal of Medicine, 1982, 307, 573–579.

12.

Marshall, E. EPA faults classic lead poisoning study. Science, 1983, 222, 906–907.

13.

McCarthy, D. McCarthy Scales of Children's Abilities. New York: Psychological Corporation, 1972.

14.

Pearson, D.T. & Dietrich, K.N. The behavioral toxicology and teratology of childhood: Models, methods, and approaches to intervention. Neurotoxicology, in press, 1985.

15.

Perino, J. & Ernhart, C. B. . The relation of subclinical lead level to cognitive and sensorimotor impairment in black preschoolers. Journal of Learning Disabilities 1974, 7, 616–620.

16.

Scarr, S. & Yee, D. Heritability and educational policy: Genetic and environmental effects on I.Q. aptitude and achievement. Educational Psychology, 1980, 15, 1–22.

17.

United States Environmental Protection Agency. Independent peer review of selected studies concerning neurobehavioral effects of lead exposures in nominally asymptomatic children: Official report of findings and recommendations of an interdisciplinary expert review committee, 1983, EPA-600/8-83-028A.

18.

Yamins, J. The relationship of subclinical lead intoxication to cognitive and language functioning in preschool children, 1976. Unpublished doctoral dissertation, Hofstra University. Hempstead, NY.