As discussed in September 14 webinar hosted by the Collaborative on Health and the Environment, a National Institute of Environmental Health Sciences-funded literature review study found evidence of increased biological indicators of liver damage from PFAS exposure in rodents and humans. Notably, the studies reviewed focused on legacy PFAS: perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid (PFHxS). Many companies are moving away from the manufacture and use of these legacy PFAS.  The study did not analyze impacts from the growing number of substances replacing legacy PFAS (referred to as GenX), though the U.S. EPA has started evaluating human health toxicity from GenX chemicals, specifically Hexafluoropropylene Oxide (HFPO) Dimer Acid and its ammonium salts. These substances are the two main chemicals associated with GenX processing. The U.S. EPA found health effects from oral doses of GenX in animal studies. With states and the federal government moving to regulate PFAS and GenX in drinking water, surface water, soil, and under other programs, regulators are likely to rely on the latest research in deciding which substances should be regulated.