Relationship between childhood blood lead levels and stature.

The second National Health and Nutrition Examination Survey, 1976 to 1980, incorporated medical history, physical examination, anthropometric measurements, dietary information (24-hour recall and food frequency), laboratory tests, and radiographs. In linear regressions of adjusted data from 2,695 children aged 7 years and younger, 91% of the variance in height, 72% of the variance in weight, and 58% of the variance in chest circumference were explained by six variables: age, race, sex, blood lead level, total calories or protein, and hematocrit or transferrin saturation level. Variables that did not significantly improve the models predicting growth included family income, degree of urbanization, serum albumin, copper, iron, and zinc levels, dietary carbohydrate, fat, calcium, potassium, phosphorus, vitamin A, vitamin C, niacin, riboflavin, and thiamine. The highly significant correlation of blood lead level with growth does not contradict the established association of childhood deprivation with increased lead exposure and with nutritional deficiences known to enhance lead absorption. Blood lead level may also represent a composite marker for unidentified genetic, ethnic, environmental, and sociocultural variables, other than race, sex, and nutrition, that affect growth. However, the correlation of stature, particularly height, with blood lead levels in the range of 5 to 35 micrograms/dL is so statistically significant that it merits investigation in other surveys and consideration of the multiple biologic mechanisms by which low-level lead exposure could impair the growth of children.