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.