Blood lead (Pb) levels: further evidence for an environmental mechanism explaining the association between socioeconomic status and psychophysiological dysregulation in children.

OBJECTIVE: The authors recently reported that blood lead (Pb) was a significant mediator for the positive association between socioeconomic status (SES) and peripheral vascular responses to acute stress in children (B. B. Gump et al., 2007). The present study considers the possibility that Pb may also mediate an association between SES and cortisol responses to acute stress. DESIGN: Early childhood Pb exposure was tested as a mediator for cross-sectional associations between SES and cortisol responses. MAIN OUTCOME MEASURES: The primary outcome was cortisol responses to acute stress in 9.5-year-old children (N = 108). RESULTS: Lower family income was associated with significantly greater cortisol levels following an acute stress task. A mediational analysis confirmed that Pb was a significant mediator for this association. CONCLUSION: These results reaffirm the importance of considering the chemical environment as well as social and psychological environment when evaluating psychophysiological effects of low SES.