Prenatal organochlorine exposure and behaviors associated with attention deficit hyperactivity disorder in school-aged children

Abstract

Organochlorines are environmentally persistent contaminants that readily cross the placenta, posing a potential risk to the developing fetus. Evidence for neurodevelopmental effects at low levels of these compounds is growing, though few studies have focused on behavioral outcomes. The authors investigated the association between prenatal polychlorinated biphenyl (PCB) and p,p'-dichlorodiphenyl dichloroethylene (p,p'-DDE) levels and behaviors associated with attention deficit hyperactivity disorder (ADHD), measured with the Conners' Rating Scale for Teachers (CRS-T), in a cohort of 607 children aged 7-11 years (median age, 8.2 years) born in 1993-1998 to mothers residing near a PCB-contaminated harbor in New Bedford, Massachusetts. The median umbilical cord serum level of the sum of 4 prevalent PCB congeners (118, 138, 153, and 180) was 0.19 ng/g serum (range, 0.01-4.41 ng/g serum). The authors found higher risk for ADHD-like behaviors assessed with the CRS-T at higher levels of PCBs and p,p'-DDE. For example, the authors found higher risk of atypical behavior on the Conners' ADHD Index for the highest quartile of the sum of 4 PCB congeners versus the lowest quartile (risk ratio = 1.76, 95% confidence interval: 1.06, 2.92) and a similar relation for p,p'-DDE. These results support an association between low-level prenatal organochlorine exposure and ADHD-like behaviors in childhood.

Figure 1.

Adjusted risk ratios for behaviors associated with attention deficit hyperactivity disorder (ADHD) among school-aged children (n = 573) born in New Bedford, Massachusetts, in 1993–1998, according to umbilical cord serum levels of A) the sum of 4 polychlorinated biphenyl (PCB) congeners (118, 138, 153, 180), B) the sum of mono-ortho toxic equivalency factor-weighted PCB congeners (TEQ), and C) p,p′-dichlorodiphenyl dichloroethylene (p,p′-DDE). Behaviors associated with ADHD were assessed using 4 subscales of the Conners’ Rating Scale for Teachers: Conners’ ADHD Index, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) Inattention, DSM-IV Impulsive-Hyperactive, and DSM-IV Total. Values were dichotomized at the 86th percentile. Results for Conners’ ADHD Index were adjusted for child's age and sex and for maternal age, marital status, smoking during pregnancy, alcohol consumption during pregnancy, local fish consumption during pregnancy, and illicit drug use. All DSM-IV outcomes were adjusted for child's age and sex and for maternal age, marital status, smoking during pregnancy, and Home Observation for Measurement of the Environment score. A statistically significant P value for trend (P < 0.05) was detected for A) the sum of 4 PCBs and all outcomes, except for DSM-IV Hyperactivity; B) TEQ and all outcomes; and C) p,p′-DDE and Conners’ ADHD Index and DSM-IV Total. Bars, 95% confidence interval.