BACKGROUND: Organohalogen compounds (OHCs), i.e. polychlorinated biphenyls (PCBs, are wide-spread environmental pollutants known to be neurotoxic for the developing brain. The hydroxylated metabolites of PCBs, OH-PCBs, might be even more toxic due to their structure and interference with thyroid hormone metabolism. We found that prenatal exposure to OH-PCBs was associated with thyroid hormone metabolism at toddler age. Little, however, is known about the neurotoxicity of OH-PCBs in humans.
OBJECTIVES: To determine whether prenatal background exposure to OHCs has an effect on mental and motor development in children at the age of 18 and 30 months.
METHODS: One hundred and eighty-one healthy mother-infant pairs were included in this observational study performed in the Netherlands. We measured maternal pregnancy levels of PCB-153 and three OH-PCBs. In one part of the cohort we measured another nine PCBs and three OH-PCBs and in the other part we measured five brominated diphenyl ethers (BDEs), dichloro-diphenyldichloroethylene (p,p'-DDE), pentachlorophenol (PCP), and hexabromocyclododecane (HBCDD). We used the mental development index (MDI) and the motor development index (PDI) of the Bayley Scales of Infant Development II (BSID-II) to assess children's mental and motor development (mean = 100; delayed score <85).
RESULTS: Higher prenatal PCB-153 levels were associated with a delayed MDI score at 18 months. None of the other compounds were associated with a delayed score, but several associations were found between OHC levels and BSID-II scores. The sum of all six OH-PCBs and three individual OH-PCBs, 4-OH-PCB-107, 3-OH-PCB-153, and 4'-OH-PCB-172, correlated positively with MDI at 30 months. The compound 3'-OH-PCB-138 showed a similar trend. A higher 4-OH-PCB-187 was associated with a lower MDI at 18 months. We found a similar trend for higher BDE-99. Higher BDE levels were associated with higher PDI at 18 months. The levels of p,p'-DDE-, PCP, and HBCDD were not associated with BSID-II scores at 18 months.
CONCLUSIONS: Higher prenatal levels of PCB-153 were associated with a delayed MDI score at 18 months. None of the other compounds were associated with a delayed score, but several associations were found between OHC levels and BSID-II scores. Prenatal OH-PCBs were positively associated with mental development at 30 months, whereas one OH-PCB was negatively associated at 18 months. BDE levels were positively associated with psychomotor development. Prenatal p,p'-DDE, PCP, and HBCDD levels were not associated with neurodevelopment at 18 months.