In Brief

When a mother has traces of polychlorinated biphenyls (PCBs)--a group of industrial chemicals linked with behavioral and biological harm--in her body, do the benefits of breastfeeding outweigh the risks of exposing her infant to more PCBs? There may be no right answer, according to research published in the January issue of Neuropsychology (Vol. 18, No. 1).

In the study, Dutch researchers Hestien J.I. Vreugdenhil, PhD, and colleagues found lasting neuropsychological effects in infants who were exposed to PCBs through breast milk as well as those who had prenatal exposure to the chemicals. Although PCBs are now banned in many places, the chemicals still make their way into humans through environmental pollution, such as by eating fish from a PCB-polluted river. The researchers measured the levels of PCBs in 207 pregnant Rotterdam women. They also checked for PCBs in the breast milk of the mothers who breastfed their babies--about half of the cohort. When the children were 9 years old, the researchers invited the 104 children with the highest and lowest PCB exposure levels for follow-up neuropsychological testing; about 80 percent agreed to participate.

The researchers found that both high- and low-exposure babies who were breastfed for 17 or more weeks scored lower than formula-fed babies on the Tower of London (TOL) test, a measure of executive function in which children plan how to complete a complex task in a specified number of steps. The researchers posit that because areas of babies' brains--such as the frontal cortex, which is associated with planning and executive function--continue to develop after birth, infants are more likely to experience negative effects of PCBs in breast milk. However, the study also found that these same breastfed babies did better on tests of spatial organization and equally well on reaction-time tests. Since the breast milk of mothers with more PCBs was correlated with both positive and negative effects, further studies are needed to weigh the costs and benefits of breastfeeding when women have PCBs in their bodies, the authors say.

In addition, the study confirmed previous findings that prenatal exposure to PCBs induces neurological changes: Children exposed to higher PCB levels had longer and more varied reaction times and scored lower on the TOL than children with low PCB exposure. The varied effects of PCBs show that the chemicals probably affect the prenatal brain in diffuse or multifocal ways.