Environmental exposure to polychlorinated biphenyls (PCBs) and dioxins - Consequences for longterm neurological and cognitive development of the child. A Review

Polychlorinated biphenyl's (PCBs) and dioxins are environmental pollutants. Calculated on a body weight basis, prenatally as well as postnatally throu gh breast-feeding, large amounts are transferred from mother to the child. Formula is free of these substances. Considering their potential developmen tal neurotoxicity, we investigated long-term effects of perinatal exposure to PCBs and dioxins on neurological and cognitive development. Methods. A g roup of 418 infants were followed from birth up to 6 years of age. Half of them were fully breast fed (BF) for at least 6 weeks. Prenatal PCB exposure was measured from cord and maternal blood. Postnatal exposure was reflecte d by PCB and dioxin levels in breast and formula milk and plasma PCB concen trations at 42 months of age. Both neurological and cognitive development w ere taken as outcome variables at 18, 42 months and at 6 years of age. At 1 8 and 42 months neurological condition was evaluated according to Hempel an d Touwen and at 6 years of age according to Touwen. Condition was evaluated in terms of optimality. Separately, the fluency of movements was scored. C ognitive abilities were measured at 18 months by means of the Bayley Scales of Infant Development, at 42 months of age by the Kaufman Assessment Batte ry for Children (K-ABC) and at 6 years of age by the McCarthy Scales. Resul ts. At 18 months of age cognitive development was not affected by either pr e- or postnatal exposure to the measured PCBs and dioxins. However, neurolo gical examination showed an adverse effect of prenatal exposure to the meas ured pollutants on the neurological optimality score. At 42 months of age w e found negative associations between prenatal PCB exposure and cognitive d evelopment. However, no effect was demonstrated of postnatal exposure to th e measured pollutants. Neurological development was not affected by either pre- or postnatal exposure to PCBs and dioxins. At 6 years of age the preli minary results showed no evidence that cognitive and neurological developme nt are affected by pre- and postnatal exposure to these pollutants. Despite a higher PCB exposure from breast milk we found at 18 months, 42 months of age, and at 6 years of age a beneficial effect of breast feeding on the qu ality of movements, in terms of fluency. Conclusion. These data support the evidence obtained from similar studies in the USA that prenatal exposure t o PCBs may have subtle negative effects on early neurological and cognitive development of the child. Further studies are required to evaluate these f indings in other parts of the world. Our studies showed consistently a bene ficial effect of breast-feeding on brain development from 18 months up to s chool age.