Prenatal Exposure to Polychlorinated Biphenyls and Attention at School Age

Abstract

ABSTRACT A previous study demonstrated lower IQ and reading comprehension scores at age 11 years in children whose mothers had eaten Lake Michigan fish contaminated by polychlorinated biphenyls (PCBs). The present prospective longitudinal study was designed to learn which specific elements of cognitive function are primarily affected. All 167 mothers had consumed the equivalent of at least 11.8 kg of Lake Michigan salmon or lake trout over a 6-year period. At age 11 years, 148 children were examined by a battery of 15 neuropsychologic tests. The tests were designed to evaluate 4 dimensions of attention function: sustained attention, focused attention, executive function, and working memory. Samples of umbilical cord serum and maternal milk were analyzed for PCBs by gas chromatography. Few associations with specific neuropsychologic end points were significant at age 11 years. There were deficits in digit cancellation, memory, and reaction time tests. Visual–spatial rotation efficiency remained intact. Adverse cognitive effects were much more frequent and also more marked in children who were not breast fed. Prenatal PCB exposure was associated with impulsivity on a number of different tasks. Highly exposed children were less able to inhibit their responses. Nevertheless, examiner-rated activity level was not significantly increased. The children were able to sustain attention when doing a relatively simple, repetitive task. Associations with executive function were not clear. Nonbreast fed children performed less well on several tests of working memory. The findings were not meaningfully altered when controlling for blood lead concentration. These findings are in accord with previous reports that children who are not breast fed are more vulnerable to PCB exposure in utero. It is not clear whether this protective effect is related to nutrients in breast milk or to a higher quality of intellectual stimulation that often is provided by mothers who breast feed their infants.