Functional Toxicology The number of man-made chemicals continues to grow yet we have a limited understanding of the biological effects of the vast majority. Our group has pioneered the use of a functional approach to comprehensively assess and identify key genes, processes and pathways underlying the eukaryotic cellular response to chemical toxicity. Other genomic approaches do not functionally assess the role of each gene/protein/metabolite in response but only identify a correlation with environmental stressors. As such, these observations do not identify a causal link between exposure, gene/protein/metabolite level, and phenotypic outcome. In contrast, functional approaches directly identify the genes necessary for cellular survival in a toxicant exposure. We have used this approach to better understand the mechanism of action of multiple chemical contaminants including arsenicals, benzene metabolites, TCE metabolites, UV filters and electron transport chain complex inhibitors. We identified several genes and pathways that are may play a role in human susceptibility for these compounds. Most recently we have developed similar approaches in mammalian cells using CRISPR based approaches.