Growth of infants' length, weight, head and arm circumferences in relation to low levels of blood lead measured serially

To determine whether levels of blood lead during gestation and infancy that are below the CDC action level of 10 μg/dl affect infant growth, we studied 211 disadvantaged mother-infant pairs from Albany, NY. Mothers' lead levels were low (second trimester x̄ 5 2.8 μg/dl) as were infants' (x̄ 5 3.3 μg/dl at 6 months; 6.4 μg/dl at 12 months). Multiple linear regression analyses showed that second trimester lead levels were related to reduced head circumference at 6 and 12 months. Infants of mothers with second trimester lead at or above the median (≥3 μg/dl) exhibited negative associations between blood lead and head circumference at 6 and 12 months, and with weight-for-age, weight-for-length, and upper arm circumference at 6 months, but those below the median did not. Infants' 6-month lead level was related to head circumference at 12 months in the total sample, and in the subsample of infants whose blood lead was above the infants' 6-month blood lead median. Infants were also grouped by changes in their relative blood lead status, that is, above vs. below the median, from second trimester to 12 months of age. Infants whose lead levels changed from above to below the median were larger than infants whose lead levels went from below to above the median. The results suggest that lead may affect some dimensions of infant growth at levels below 10 μg/dl, but effects of lead levels less than 3 μg/dl are not evident in this sample.