Identifying critical windows of exposure for children's health

Several authors have considered the importance of exposure timing and how t his affects the outcomes observed, but no one has systematically compiled p reconceptional, prenatal, and postnatal developmental exposures and subsequ ent outcomes. Efforts were undertaken to examine the information available and to evaluate implications for risk assessment for several areas: ai resp iratory and immune systems, b) reproductive system. c) nervous system, di c ardiovascular system, endocrine system, and general growth, and e) cancer. Major conclusions from a workshop on "Critical Windows of Exposure for Chil dren's Health" included ai broad windows of sensitivity can be identified f or many systems but detailed information is limited; b) cross-species compa risons of dose to target tissue and better data on the exposure-dose-outcom e continuum are needed; ci increased interaction among scientific disciplin es can further understanding by using laboratory animal results in designin g epidemiological studies and human data to suggest specific laboratory stu dies on mechanisms and agent-target interactions; and d) thus far, only lim ited attention has been given to peripubertal/adolescent exposures, adult c onsequences of developmental exposures, and genome-environment interactions . More specific information on developmental windows will improve risk asse ssment by identifying the most sensitive window(si for evaluation of dose-r esponse relationships and exposure, evaluation of biological plausibility o f research findings in humans, and comparison of data across species. In pu blic health and risk management, information on critical windows may help i dentify especially susceptible subgroups for specific interventions.