Protect Drinking Water from PFAS Act of 2021 This bill requires the Environmental Protection Agency (EPA) to address the level of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in drinking water. PFAS are man-made and may have adverse human health effects. A variety of products contain PFAS, such as nonstick cookware or weatherproof clothing. In addition, the EPA must publish a maximum contaminant level goal (MCLG) and promulgate a national primary drinking water regulation for PFAS. The MCLG and regulation must be protective of the health of subpopulations that may be at greater risk than the general population of adverse health effects from exposure to PFAS in drinking water.