On Feb. 26, the Environmental Quality Board (EQB) took another meaningful step toward finalizing Pennsylvania's first state-established maximum contaminant levels (MCLs) for regulating contaminants in drinking water. On that date, the EQB published a proposed rule to amend 25 Pa. Code Ch. 109 (Safe Drinking Water) to establish MCLs for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), two of the most common PFAS. PFOA and PFOS are just two of a group of thousands of PFAS, manmade chemicals used in various consumer, commercial and industrial manufacturing processes since the 1940s. PFAS have commonly been used to imbue products with water-, stain-, and heat-resistant properties and as ingredients in aqueous film forming foams (AFFF) used to extinguish flammable liquid fires (e.g., those that might occur on airports or military bases). PFAS do not break down naturally in the environment and have thus been called "forever chemicals." Due to these properties and their ubiquitous nature, PFAS have been found in various environmental media, such as groundwater (including drinking water), plants, animals, and in humans, and evidence suggests that PFAS exposure can lead to adverse health effects. In the absence of definitive federal action to regulate PFAS, many states, including Pennsylvania, have in recent years taken steps to investigate, understand, and regulate PFAS.