Can the National Health and Nutrition Examination Survey III (NHANES III) data help resolve the controversy over low blood lead levels and neuropsychological development in children?

The National Health and Nutrition Examination Survey III (NHANES III) was designed to provide national estimates of the health and nutritional status of the United States population aged 2 months and above. A Youth data subset includes individuals from ages 2 months to 16 years totaling 13,944 individuals. Lanphear, Dietrich, Auinger, and Cox [U.S. Department of Health and Human Services, Public Health Reports, Public Health Report 2000, Vol. 115, p. 521] examined these data and concluded that deficits in cognitive and academic skills associated with lead exposure occur at blood lead concentrations of less than 5 μg/dl. Attempts to replicate and extend these findings reveal serious shortcomings in the NHANES III data that center around missing data, odd distributions of blood lead levels as well as cognitive and academic scores, and potential inaccuracies in the data collection itself. A review of these issues is presented along with a series of empirical analyses of the data under multiple sets of assumptions leading to the conclusion that the NHANES III data are inherently inadequate for use in addressing neurodevelopmental issues. Policy issues and scientific issues related to cognitive and other neurodevelopmental phenomena should not be considered on the basis of the NHANES III Youth dataset.