The landscape of chemical risk assessment is rapidly changing as a result of phenomenal advances in molecular systems biology, reports from the National Research Council, improved understanding of gene-environment interactions, and volumes of new toxicity data from the United States and Europe. In response, EPA initiated the "Advancing the Next Generation of Risk Assessment" (NexGen) effort, which aims to create a faster and more cost effective system for chemical risk assessment by incorporating new chemical testing data and advances in molecular and systems biology technologies