Dr. Ari S. Lewis, MS is a Principal at the Gradient. She has led and contributed to a variety of projects, including product safety evaluations, regulatory comments, green chemistry assessments, and technical support for the utility and mining industries. She also has particular expertise in risk assessment of arsenic and coal combustion product regulatory issues. In this capacity, Ms. Lewis has both published and presented extensively on the carcinogenic risks of arsenic and provided direct input to US EPA on arsenic regulatory issues. Ms. Lewis also has expertise in developing quantitative human health risk criteria for chemicals with limited toxicity data. Before joining Gradient, Ms. Lewis earned her M.S. at Cornell University; her thesis project investigated the molecular and cellular responses to arsenic exposure during early animal development.