[Profiling prospective birth cohort studies on relationship between environment and children's health: various issues and aspects involved in evaluating development in children].

Polychlorinated biphenyls (PCBs) and dioxins are persistent environmental pollutants. The effects of these pollutants on neurodevelopment in children have been assessed in longitudinal studies performed in areas with low-level contamination of PCBs and dioxins. Some of these studies have shown that the PCBs and dioxins induced adverse effects on the neurodevelopment of children. However, other studies did not reveal any negative effects of these chemicals on development. Thus, consistent results describing the effects of low-level PCB and dioxin exposure on children's development have not been obtained. To study the effects of these agents on the neurodevelopment of children, it is essential to identify the target of the study, determine the duration of the study, and devise a protocol for performing the studies, as these are important factors that affect research findings. Furthermore, detailed evaluations of neurodevelopment should be performed by longitudinal methods to obtain reliable measurements of outcomes. However, it is necessary to assess the burden on subjects; this step can help reduce the loss of subjects and determine the most suitable approach to evaluating neurodevelopment.