In the first integrative synthesis of studies examining the effects of prenatal exposure to polychlorinated biphenyls (PCBs) on cognitive development in children, researchers in Canada have reported consistent findings across studies showing an association between increased exposures to PCBs during pregnancy and decreased cognitive functioning in children.

Conducted by researchers at the School of Psychology at the University of Lavel, in Quebec, Canada, Olivier Boucher and colleagues reviewed data from nine prospective longitudinal cohort studies that had looked at the effect of prenatal PCB exposure on child cognitive development. The review was published in the January Edition of Environmental Health Perspectives.

The studies reviewed were conducted between 1959 and 2008 in North America, Northern Europe, and Japan. Food was the main source of exposure in all studies and included fish, dairy products, meat products, and background exposure from the general food supply. Samples collected to estimate in-utero PCB exposure in women included blood samples taken during pregnancy, blood samples taken at or around the time of delivery, cord blood samples taken at birth, and breast milk samples taken within a few months after birth. Cognitive testing of children was done between 3 months of age and 11 years of age.

Key results reported included findings in four of the six studies that used IQ-type tests of lower IQ scores among children with higher in-utero PCB exposures. Effects were consistently found suggesting an effect of in-utero PCB exposure on the speed of information processing, verbal abilities, and visual recognition memory. Different studies also found that higher levels of in-utero exposure to PCBs were associated with diminished executive functioning which includes cognitive abilities like planning and memory. The authors hypothesized that such effects may be the result of the prefrontal cortex portion of the brain being particularly vulnerable to PCB exposure during development.

PCBs are a class of man-made chlorinated compounds (known as congeners) that are either oily liquids or solids. PCBs are often colorless and have no smell or taste. PCBs often exist as vapor around a primary exposure source (e.g. from building materials). Although the primary source of PCBs is often from building materials and manufacturing, PCB vapors are transferred to plants and animals which are then consumed – thus passing PCBs from the environment, to another organism and then to another organism. As such, a major source of exposure for PCBs is from food. PCB exposure can also be a consequence of occupation. PCB bioaccumulation can also be passed from one generation to the next via transfer from a Mother to a fetus during pregnancy or afterwords via breast milk.

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To learn more about the effect of chemicals during pregnancy read: Fifteen Strategies for Reducing Chemical Exposures when Pregnant, Planning a Pregnancy, or Breastfeeding.

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