## 1 Introduction
### Environmental  
Over the past two decades, concern has increased over the adverse impact PFAS compounds have on human health and the environment as a probable connection between PFAS exposure and diseases such as cancer and thyroid disease [49; 57; 58; 59]. Two of the most notable PFAS non-polymers that have garnered considerable attention are PFOA and PFOS due to their previous use as part of aqueous film forming foams (AFFs) used to fight fires [3; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74]. Research to determine how PFAS compounds affect health is still relatively limited; however, numerous studies have been completed on AFFF-impacted sample areas to determine the extent to which these toxic compounds have accumulated in soil, wastewater, animals, and humans [67; 68; 70].  
The Environmental Protection Agency (EPA) is the lead organization in identifying, monitoring, and regulating PFAS throughout the United States. Most recently, the EPA released an action plan in February 2019 to address PFAS concerns [23]. Moreover, in February 2020, the EPA updated the action plan on addressing PFAS contaminant detection with various methods to include testing for 29 PFAS chemicals in drinking water via EPA Methods 533 [53] and 537.1 [54] and testing for PFAS in non-potable water via SW-846 Method 8327 [75]. They are also updating the Significant New Use Rule (SNUR) which requires PFOA manufacturers to notify the EPA at least 90 days in advance before manufacturing with these chemicals [76]. In addition to testing, the EPA is supporting government agency cleanup efforts, publishing interim guidance on the proper destruction and disposal of PFAS using high temperature incineration, and taking measures against facilities that violate current PFAS manufacturing requirements. They are also working alongside the U.S. Department of Agriculture (USDA) and Food and Drug Administration (FDA) to develop analytical methods for agricultural and food products. Lastly, to better understand human health hazards associated with PFAS, they are currently researching human health effects associated with seven common PFAS. Overall, the EPA will continue to make progress on addressing PFAS detection and remediation under guidelines established from the Safe Drinking Water Act (SDWA) [77] passed by Congress in 1974 (amended in 1986 and 1996); the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [78] passed in 1980 (amended in 1986); the Resource Conservation and Recovery Act (RCRA) [79] passed in 1976 (amended in 1984 and 1986); and the Toxic Substances Control Act (TSCA) [80] passed in 1976 but amended in 2016 by the Frank R. Lautenberg Chemical Safety for the 21 st Century Act [81].  
The European Environment Agency (EEA), which has 32 European member states, has also taken measures to regulate and monitor PFAS, specifically PFOS, throughout countries within the European Union (EU) [21]. Persistent organic pollutants are a classification that encompasses different chemicals and makes classification and regulation easier; many PFAS are listed as POPs under the 2001 Stockholm Convention, with PFOA and PFOS added in 2009 [82]. PFOA and PFOS are listed to be eliminated or restricted in use, respectively. Currently, PFOS is regulated under EU Regulation No 2019/1021, with specific guidance on marketing, manufacturing, use, and waste management [83]. The Stockholm Convention continues to publish effectiveness evaluations on specific POPs, with the most recent report on PFOS from 2017 with the results stating that the production of PFOS has dropped significantly, but specifics are still unknown due to the lack of data [84]. Many countries within the European Union have set drinking water limits for PFAS [85] and are continuing research to determine the seriousness and spread of these compounds.