Workshop to identify critical windows of exposure for children's health: Neurobehavioral work group summary

This paper summarizes the deliberations of a work group charged with addres sing specific questions relevant to risk estimation in developmental neurot oxicology. We focused on eight questions. a) Does it make sense to think ab out discrete windows of vulnerability in the development of the nervous sys tem? If it does, which time periods are of greatest importance? b) Are ther e cascades of developmental disorders in the nervous system? For example, a re there critical points that determine the course of development that can lead to differences in vulnerabilities at later times! c) Can information o n critical windows suggest the most susceptible subgroups of children (i.e. , age groups, socioeconomic status, geographic areas, race, etc.)! di What are the gaps in existing data for the nervous system or end points of expos ure to it! e) What are the best ways to examine exposure-response relations hips and estimate exposures in vulnerable life stages! f) What other exposu res that affect development at certain ages may interact with exposures of concern! g) How well do laboratory animal data predict human response! h) H ow can all of this information be used to improve risk assessment and publi c health (risk management)? In addressing these questions, we provide a bri ef overview of brain development from conception through adolescence and em phasize vulnerability to toxic insult throughout this period. Methodologica l issues focus on major Variables that influence exposure or its detection through disruptions of behavior, neuroanatomy, or neurochemical end points. Supportive evidence from studies of major neurotoxicants is provided.