The effects of environmental exposure to polychlorinated biphenyls (PCB) and dioxins on cognitive abilities in Dutch children at 42 months of age were assessed at the Sophia Children’s Hospital, Rotterdam, The Netherlands. Maternal plasma and breast milk concentrations were compared with scores of cognitive function. Maternal plasma total PCB concentrations were associated with lower cognitive functioning, and the effect was related to the degree of prenatal in utero exposure. Lactational and current childhood exposure to PCBs and dioxins were not related to 42-month cognitive performance. 
COMMENT. The developing fetal brain is particularly sensitive to environmental toxins. Prenatal in utero exposure to PCBs causes impaired cognitive performance in children, whereas lactational and childhood exposure may not have adverse effects on learning. These results are in agreement with previous Chinese poisoning and Michigan fish exposure studies. Although deficits are often small, the implications of low-level PCB exposure may be compared to that of lead exposure. Furthermore, the effects on intellectual performance are long-lasting, and ADHD is a potential complication. (Progress in Pediatric Neurology III. PNB Publ, 1997;pp226-8).