We propose to test three specific hypotheses for children experiencing a range of low-to-moderate prenatal BLL concentrations:

1)Higher BLLs will be associated with higher parent ratings of the child on negative temperamental attributes (grizzly, fretful, stubborn, demanding, unresponsive, active) and lower ratings on positive attributes (happy, alert, cuddly, sociable) at 4 weeks of age when the infants also have polymorphisms previously related to negative emotionality or heightened behavioral reactivity.

2)Higher BLLs will be associated with higher parent ratings of activity, approach, intensity, and distractibility at 6 and 24 months among children who also have polymorphisims previously shown to be related to negative emotionality or heightened behavioral reactivity.Higher BLls will be associated with lower scores on rhythmicity, adaptability, mood, persistence and threshold in the presence of the same gene polymorphisms.

3)Higher BLLs will not be associated with negative temperament traits at 6 and 24 months among children who have gene polymorphisms previously shown to be related to altruism or self-regulation.

In addition to gene-environment interactions, we will test for interactions between maternal hemoglobin and lead levels on the same outcomes to understand if maternal nutritional status acts as a protective or susceptibility factor for the assocation between lead exposure and temperament.