UC Berkeley

Background

Half the world's population is at risk for malaria. Indoor residual spraying (IRS) with insecticides has been effective in controlling malaria, yet the potential neurotoxicity of these insecticides is of concern, particularly for infants exposed in utero.

Objectives

To determine the association of prenatal exposure to DDT/DDE and pyrethroid insecticides and behavioral/emotional problems in two-year-old children.

Methods

The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) birth cohort in South Africa, measured concentrations of p,p'-DDT and p,p'-DDE in maternal serum and pyrethroid metabolites (cis-DBCA, cis-DCCA, trans-DCCA, and 3-PBA) in maternal urine collected during pregnancy. At 2 years, 683 mothers were interviewed about their children's behavior and emotional development, using the Child Behavior Checklist (CBCL). We examined associations between behavioral or emotional problems and biomarkers of prenatal insecticide exposure.

Results

Maternal serum p,p'-DDT concentrations were associated with heightened withdrawn behavior in 2-year olds, with a 0.24 increase in raw scores (95%CI = 0.00, 0.49) and a 12% increase (95%CI = 1.01, 1.23) in risk of being at or above the borderline-clinical level, per 10-fold increase in concentrations. Ten-fold increases in p,p'-DDT and p,p'-DDE were related to 30% (RR = 1.30; 95%CI = 1.01, 1.67) and 39% (RR = 1.39; 95%CI =1.01, 1.91) higher risks, respectively, for increased oppositional-defiant behavior. p,p'-DDE concentrations were also related to increased risk of ADHD-related problems (RR = 1.30; 95%CI = 0.98, 1.72). Maternal urinary concentrations of cis-DBCA and 3-PBA were associated with increased risk of externalizing behaviors (RR = 1.30; 95%CI = 1.05, 1.62; RR = 1.35, 95%CI = 1.03, 1.78 per 10-fold increase, respectively), with some evidence of an association between cis-DBCA and affective disorders (RR = 1.25; 95%CI = 0.99, 1.56). Some associations with maternal pyrethroid concentrations were stronger in girls than boys.

Conclusions

Prenatal exposure to DDT and pyrethroid insecticides may be associated with maternally-reported behavioral problems in two-year-old children. Given their long history and continued use, further investigation is warranted.