several authors have considered the importance of exposure timing and how this affects the outcomes observed , but no one has systematically compiled preconceptional , prenatal , and postnatal developmental exposures and subsequent outcomes . 
 efforts were undertaken to examine the information available and to evaluate implications for risk assessment for several areas : a ) respiratory and immune systems , b ) reproductive system , c ) nervous system , d ) cardiovascular system , endocrine system , and general growth , and e ) cancer . 
 major conclusions from a workshop on " critical windows of exposure for children 's health " included a ) broad windows of sensitivity can be identified for many systems but detailed information is limited ; b ) cross - species comparisons of dose to target tissue and better data on the exposure - dose - outcome continuum are needed ; c ) increased interaction among scientific disciplines can further understanding by using laboratory animal results in designing epidemiological studies and human data to suggest specific laboratory studies on mechanisms and agent - target interactions ; and d ) thus far , only limited attention has been given to peripubertal / adolescent exposures , adult consequences of developmental exposures , and genome - environment interactions . 
 more specific information on developmental windows will improve risk assessment by identifying the most sensitive window(s ) for evaluation of dose - response relationships and exposure , evaluation of biological plausibility of research findings in humans , and comparison of data across species . in public health and risk management , 
 information on critical windows may help identify especially susceptible subgroups for specific interventions.imagesfigure 3