Attention, activity level, and lead exposure at 18 months.

A structured problem-solving task was used to evaluate the effects of lead (Pb) exposure on the activity patterns and attention of 18-month-old infants. After statistically controlling for the influence of the caretaker's attempts to support and teach the infant during the task, multivariate techniques were used to examine the residual variances to detect any effects of prenatal or postnatal Pb exposure. Contrary to expectations, no relationship was found between Pb exposure and measures of attention. Activity level was found to be negatively related to blood Pb level. The suggested suppression of behavior was inconsistent with reports of hyperactivity found in school children with elevated Pb level, but is consistent with observations of lethargy in infants with iron deficiency. To examine this alternative, free erythrocyte protoporphyrin (FEP) levels, which are elevated both in the presence of elevated Pb and in iron deficiency, were incorporated into the regression model. FEP was the best predictor of room movement, as indicated by a backward elimination analysis that removed all Pb measures from the model. However, none of the other measures of hematopoietic status were related to behavior. The suppression of activity level, if a reliable effect, is very small, and only weakly though significantly related to FEP level.