Differential association of lead on length by zinc status in two-year old Mexican children
The National Health and Nutrition Survey 1976-1980 demonstrated the inverse association of blood lead 8-35 micrograms/dl (0.4-1.7 microM) with height and weight in 2680 children 1-7 yr old. Growth has not been examined. A retrospective pilot study was made of growth, 0-42 mo, for 54 children found to have erythrocyte protoporphyrins greater than 35 micrograms/dl (0.6 mM) at 12-23 mo. For 24/54, all blood leads were less than 30 micrograms/dl (1.2 microM), with a peak annual mean of 18.5 micrograms/dl (0.9 microM); for 30/54, mean blood lead was 46.7 micrograms/dl (2.2 microM) at 12-23 mo with all subsequent blood leads greater than or equal to 30 micrograms/dl (1.2 microM). In both groups the mean height and weight at birth were at the 25th percentile. The high-lead children had increased weight velocity at 15 mo of age and were heavier at 24 mo. Weight gain related to total caloric intake, supporting food consumption, and hand-to-mouth behavior as significant factors in an increased blood lead ages 9-24 mo. The monthly directional change of height and weight percentiles after 24 mo, however, showed a decreased frequency of upward shifts when blood lead was greater than or equal to 30 micrograms/dl. Although an early high food intake appears to contribute to high blood lead by increasing the intake of lead from food and mouthing, persistent increases in the high blood lead and erythrocyte protoporphyrins were associated with subsequent growth retardation.