The detection of certain per- and polyfluoroalkyl substances (PFAS) in some public water supplies has generated public concern and increased congressional attention to the U.S. Environmental Protection Agency's (EPA) efforts to address these substances. Over the past decade, EPA has been evaluating several PFAS under the Safe Drinking Water Act (SDWA) to determine whether national drinking water regulations may be warranted. EPA has not issued SDWA regulations for any PFAS but has taken various actions to address PFAS contamination. Using SDWA authorities, in 2016, EPA issued non-enforceable health advisories for two PFASâperfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)âin drinking water. The 116 th Congress has held hearings on PFAS and passed legislation to address PFAS contamination issues through various authorities and departments and agencies. The National Defense Authorization Act (NDAA) for Fiscal Year 2020 ( P.L. 116-92 ) includes several PFAS provisions involving the Department of Defense (DOD) and other federal agencies. Of the EPA provisions related to drinking water, Title LXXIII, Subtitle A, directs EPA to require public water systems to conduct additional monitoring for PFAS and establishes a grant program for public water systems to address PFAS and other emerging contaminants. On January 10, 2020, the House passed H.R. 535 , a broad PFAS bill that would direct EPA and other federal agencies to take numerous actions to address PFAS. Among its provisions, H.R. 535 would amend SDWA to direct EPA to regulate PFAS in drinking water and would authorize grants for communities for treatment technologies. Other bills would variously direct EPA to take regulatory and other actions under several environmental statutes, including SDWA. Similar to H.R. 535 , multiple SDWA bills would require EPA to establish final or interim drinking water regulations for some or all PFAS, require monitoring for more of these substances, or authorize grants to assist communities in treating PFAS in drinking water. (See Table 1 .) PFAS are a large, diverse group of fluorinated compounds, some of which have been used for decades in a wide array of commercial, industrial, and U.S. military applications. Since the 1940s, more than 1,200 PFAS compounds have been used in commerce, and about 600 are still in use today. The chemical characteristics of PFAS have led to the widespread use of these substances for beneficial purposes (such as firefighting) and in the processing and manufacture of many commercial products, such as nonstick cookware, food wrapper coatings, stain-resistant carpets, waterproof clothing, and food containers. The two PFAS most frequently detected in water supplies are PFOA and PFOS. Since 2002, U.S. manufacturers have phased out the production and most uses of PFOS. In coordination with EPA, manufacturers completed the phase-out of PFOA production by 2015. EPA reports that food and consumer products represent a large portion of exposure to PFOA and PFOS, while drinking water can be an additional source in the small percentage of communities with contaminated water supplies. Among the thousands of different PFAS, few have sufficient health effects studies for determining a threshold at which adverse effects are not expected to occur. Most studies of potential health effects of PFAS have focused on PFOA and PFOS because of their predominant historical use. For those PFAS for which scientific information is available, animal studies suggest that exposure to particular substances above certain levels may be linked to various health effects, including developmental effects; changes in liver, immune, and thyroid function; and increased risk of some cancers. A discussion of these studies and their results is beyond the scope of this report. In 2016, EPA reported that public water systems in 29 states had detected at least one PFAS in their water supplies. In total, 63 public water systems serving approximately 5.5 million people reported detections of PFOA and PFOS (separately or combined) above EPA's health advisory level of 70 parts per trillion (ppt). EPA has reported that PFAS contamination of drinking water "is typically localized and associated with a specific facility." According to the Agency for Toxic Substances and Disease Registry, PFAS may have been released to surface or ground water from manufacturing sites, industrial use, use and disposal of PFAS-containing consumer products (e.g., unlined landfills), fire/crash training areas, wastewater treatment facilities, and the spreading of contaminated biosolids. A discussion of PFAS use, including at U.S. military installations, and PFAS disposal is not included in this report. Uncertainty about potential health effects that may be associated with exposure to specific PFAS above particular concentrationsâcombined with the absence of a federal health-based drinking water standardâhas posed challenges and created uncertainty for states, water suppliers and their customers, homeowners using private wells, and others regarding treatment or other potential responses. State drinking water regulators and others have called for greater federal leadership to address these substances through several federal laws and, specifically, have urged EPA to set federal drinking water standards for one or more PFAS under SDWA. Representatives of public water systems have supported EPA's commitment to follow the statutory process for regulating contaminants in drinking water, which prioritizes regulating those that occur at levels and frequency of public health concern. SDWA provides EPA with several authorities to address emerging contaminants in public water supplies and drinking water sources. These include the authority to (1) issue health advisories, (2) regulate contaminants in water provided by public water systems, and (3) issue enforcement orders in certain circumstances. For more than a decade, EPA has been using SDWA authorities to evaluate several PFASâparticularly PFOA and PFOSâto determine whether national drinking water regulations may be warranted. To date, EPA has not promulgated drinking water regulations for any PFAS but has taken a number of related actions. In February 2019, EPA issued a PFAS Action Plan, which identifies and discusses the agency's current and proposed efforts to address PFAS through several statutory authorities, including SDWA. These actions range from potential regulatory actions to public outreach on PFAS. Many of these actions support EPA's evaluation of PFAS for potential regulation under SDWA. These include research and development of analytical methods needed to accurately measure substances in drinking water, development of additional toxicity information to increase understanding of potential health risks associated with exposures to different PFAS, and research on drinking water treatment effectiveness and costs for various PFAS. EPA also plans to generate occurrence data for more PFAS to determine their frequencies and concentrations in public water supplies. Further, EPA is working with federal, state, and tribal partners to develop risk communication materials on PFAS and plans to develop an interactive map on potential PFAS sources and occurrence. Table A-1 includes EPA's selected actions and associated timelines relevant to addressing PFAS in drinking water. The challenges of regulating individual substances or categories of PFAS in drinking water are multifaceted and may raise several policy and scientific questions. Technical issues involve availability of data, detection methods, and treatment techniques for related but diverse contaminants. Scientific questions exist about health effects attributed to many individual PFAS and whether health effects can be generalized from one or a category of PFAS to others. Policy and regulatory considerations may involve setting priorities among numerous unregulated contaminants, the value of establishing uniform national drinking water standards, and the ability to demonstrate the relative risk-reduction benefits compared to compliance costs to communities associated with regulating individual or multiple PFAS. The absence of a federal health-based standard can pose challenges for states and communities with PFAS contamination. State drinking water regulators have noted that many states may face significant obstacles in setting their own standards. This report provides an overview of EPA's ongoing and proposed actions to address PFAS under SDWA authorities, with particular focus on the statutory process for evaluating PFASâparticularly PFOA and PFOSâfor potential regulation. It also reviews PFAS-related legislation introduced in the 116 th Congress, with emphasis on bills that would amend SDWA. This report does not address the status of scientific research on health effects that may be associated with exposure to one or more PFAS, nor does it discuss federal actions regarding other environmental statutes, such as the Toxic Substances Control Act (TSCA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). SDWA provides EPA with several authorities to address emerging contaminants in drinking water supplies and sources. The act authorizes EPA to promulgate regulations that include enforceable standards and monitoring requirements for contaminants in water provided by public water systems. For contaminants that are not regulated under the act, SDWA authorizes EPA to issue contaminant-specific health advisories that include technical guidance and identify concentrations that are expected to be protective of sensitive populations. In addition, if the appropriate state and local authorities have not acted to protect public health, SDWA authorizes EPA to take actions to abate an imminent and substantial endangerment to public health from "a contaminant that is present in or is likely to enter a public water system or an underground source of drinking water." SDWA specifies a multistep process for evaluating contaminants to determine whether a national primary drinking water regulation is warranted. The evaluation process includes identifying contaminants of potential concern, assessing health risks, collecting occurrence data (and developing reliable analytical methods necessary to do so), and making determinations as to whether or not regulatory action is needed for a contaminant. To make a positive determination that a national drinking water regulation is warranted for a contaminant, EPA must find that a contaminant may have an adverse health effect; it is known to occur or there is a substantial likelihood that it will occur in public water systems with a frequency and at levels of public health concern; and in the sole judgment of the EPA Administrator, regulation of the contaminant presents a meaningful opportunity for health risk reduction for persons served by water systems. SDWA Section 1412(b) requires EPA to publish, every five years, a list of contaminants that are known or anticipated to occur in public water systems and may require regulation under the act. Before publishing a final contaminant candidate list (CCL), EPA is required to provide an opportunity for public comment and consult with the scientific community, including the Science Advisory Board. In 2009, EPA placed PFOA and PFOS on the third such list (CCL 3) for evaluation. In preparing the CCL 3, EPA considered over 7,500 chemical and microbial contaminants and screened these contaminants based on their potential to occur in public water systems and potential health effects. EPA selected 116 of the contaminants on the proposed CCL based on more detailed evaluation of occurrence, health effects, expert judgement, and public input. In 2016, EPA published the fourth list, CCL 4, which carried over many CCL 3 contaminants, including PFOA and PFOS. EPA carried forward these contaminants to continue evaluating health effects, gathering national occurrence data, and developing analytical methods. To generate data on the nationwide occurrence of emerging contaminants in public water supplies, EPA is required to administer a monitoring program for unregulated contaminants. SDWA directs EPA to promulgate, every five years, an unregulated contaminant monitoring rule (UCMR) that requires public water systems to test for no more than 30 contaminants. Only a representative sample of systems serving 10,000 or fewer people is required to conduct monitoring. EPA uses data collected through UCMRs to estimate whether the occurrence of the contaminant in public water supplies is local, regional, or national in scope. UCMRs set a minimum reporting level (MRL) for each contaminant. MRLs are not health based; rather, they establish concentrations for reporting and data collection purposes. EPA makes the UCMR monitoring results available to the public and reports the number of detections above the MRL and also detections above EPA's health-based reference levels (discussed below), where available. The act includes an authorization of appropriations to cover monitoring and related costs for small systems (serving 10,000 persons or fewer). However, large systems pay UCMR monitoring and laboratory costs. In 2012, EPA issued the third UCMR (UCMR 3), under which 4,864 public water systems tested their drinking water for six PFASâincluding PFOA and PFOSâbetween January 2013 and December 2015. Among these systems, EPA reported the following monitoring results for PFOA and PFOS: 117 of the public water systems reported detections of PFOA at levels above the MRL of 20 ppt, and 95 reported detections of PFOS at concentrations above the MRL of 40 ppt. Overall, 63 of the 4,864 (1.3%) water systems that conducted PFAS monitoring reported at least one sample with PFOA and/or PFOS (separately or combined) concentrations exceeding EPA's health advisory level of 70 ppt for PFOA and PFOS. Actual exposures among individuals served by these systems would be expected to vary depending on water use and consumption. EPA estimates that these 63 water systems serve approximately 5.5 million individuals. Of the 63 systems: 9 reported detections of both PFOS and PFOA above 70 ppt; 4 reported detections of PFOA above 70 ppt; 37 reported detections of PFOS above 70 ppt; and 13 reported detections of PFOA and PFOS (combined but not separately) above 70 ppt. Systems with PFOA or PFOS detections above 70 ppt were located in 21 states, the Pima-Maricopa Indian community, and 2 U.S. territories. EPA's PFAS Action Plan notes that the agency intends to propose monitoring requirements for other PFAS when it proposes the next UCMR (UCMR 5) in 2020. As of January 2020, EPA has developed an analytical method to detect 29 PFAS in drinking water supplies. The plan states that the agency would use the monitoring data gathered through UCMR 5 to evaluate the national occurrence of additional PFAS. The agency is currently working to develop analytical methods to support monitoring for additional PFAS. SDWA requires EPA, every five years, to make a regulatory determinationâa determination of whether or not to promulgate a national primary drinking water regulationâfor at least five contaminants on the CCL. To consider a contaminant for a regulatory determination (RD), EPA requires, at a minimum, a peer-reviewed risk assessment and nationally representative occurrence data. In selecting contaminants for an RD, SDWA requires EPA to give priority to those that present the greatest public health concern while considering a contaminant's health effects on specified subgroups of the population (e.g., infants, children, pregnant women) who may be at greater risk of adverse health effects due to exposure to a contaminant. As noted above, to make a positive determination to regulate a contaminant, EPA must find that (1) a contaminant may have an adverse health effect; (2) it is known to occur or there is a substantial likelihood that it will occur in public water systems with a frequency and at levels of public health concern; and (3) in the sole judgment of the EPA Administrator, regulation of the contaminant presents a meaningful opportunity for health risk reduction for persons served by water systems. SDWA directs EPA to publish a preliminary determination and seek public comment prior to making an RD. EPA may also make RDs for contaminants not listed on the CCL if EPA finds that the statutory criteria regarding health effects and occurrence are satisfied. EPA has issued RDs for CCL 1 through CCL 3. EPA published final determinations that no regulatory action was appropriate or necessary for nine contaminants on CCL 1 (2003) and 11 contaminants (including perchlorate) on CCL 2 (2008). In the most recent RD (2016), EPA determined that regulation was not needed for four of the 116 contaminants listed on CCL 3. EPA delayed a determination on a fifth contaminant, strontium, "in order to consider additional data and decide whether there is a meaningful opportunity for health risk reduction by regulating strontium in drinking water." In 2014, when EPA published preliminary RDs for contaminants on CCL 3 (including PFOA and PFOS), UCMR 3 monitoring was underway and national occurrence data were not available. EPA did not include any PFAS among the contaminants selected for the third RD. In November 2016, EPA included PFOA and PFOS on the agency's list of unregulated contaminants for which sufficient health effect and occurrence data were available to make RDs. The next round of RDs is scheduled for 2021, although SDWA does not prevent EPA from making determinations outside of that five-year cycle. In the Fall 2019 Unified Regulatory Agenda , EPA expected to propose preliminary determinations for two PFASâPFOA and PFOSâby the end of 2019, followed by final determinations by January 2021. Once the Administrator makes a determination to regulate a contaminant, SDWA allows EPA 24 months to propose a "national primary drinking water regulation" and request public comment. EPA is required to promulgate a final rule within 18 months after the proposal. SDWA authorizes EPA to extend the deadline to publish a final rule for up to nine months, by notice in the Federal Register . For each contaminant that EPA determines to regulate, EPA is required to establish a non-enforceable maximum contaminant level goal (MCLG) at a level at which no known or anticipated adverse health effects occur and which allows an adequate margin of safety. An MCLG is based solely on health effects data and does not reflect cost or technical feasibility considerations. EPA derives an MCLG based on an estimate of the amount of a contaminant that a person can be exposed to on a daily basis that is not anticipated to cause adverse health effects over a lifetime. This amount is derived using the best available peer-reviewed studies and incorporates uncertainty factors to provide a margin of protection for sensitive subpopulations. In developing an MCLG, EPA also estimates the general population's exposure to a contaminant from drinking water and other sources (e.g., food, dust, soil, and air). After considering other exposure routes, EPA estimates the proportion of exposure attributable to drinking water (i.e., the relative source contribution). When exposure information is not available, EPA uses a default assumption that 20% of exposure to a contaminant is attributable to drinking water. EPA applies the relative source contribution to ensure that an individual's total exposure from all sources remains within the estimated protective level. The MCLG provides the basis for calculating a drinking water standard. Thus, EPA's ability to develop a drinking water regulation for a contaminant is dependent, in part, on the availability of peer-reviewed scientific studies. Drinking water regulations generally specify a maximum contaminant level (MCL)âan enforceable limit for a contaminant in public water supplies. SDWA requires EPA to set the MCL as close to the MCLG as feasible. When assessing feasibility, the law directs EPA to consider the best available (and field-demonstrated) treatment technologies, taking cost into consideration. If the treatment of a contaminant is not feasibleâtechnologically or economicallyâEPA may establish a treatment technique in lieu of an MCL. Each regulation also establishes associated monitoring, treatment, and reporting requirements. These regulations can cover multiple contaminants and, generally, establish an MCL for each contaminant covered by the regulation. Regulations generally take effect three years after promulgation. EPA may allow up to two additional years if the Administrator determines that more time is needed for public water systems to make capital improvements. (States have the same authority for individual water systems. ) The law directs EPA to reviewâand if necessary reviseâeach regulation every six years and requires that any revision maintain or provide greater health protection. For emerging contaminants of concern, data may be limited, particularly regarding a contaminant's potential health effects and occurrence in public water supplies. SDWA authorizes EPA to issue health advisories for contaminants in drinking water that are not regulated under the act. These advisories provide information on a contaminant's health effects, chemical properties, occurrence, and exposure. They also provide technical guidance on identifying, measuring, and treating contaminants. Health advisories include non-enforceable levels for concentrations of contaminants in drinking water. EPA sets health advisories at levels that are expected to protect the most sensitive subpopulations (e.g., nursing infants) from any deleterious health effects, with a margin of protection, over specific exposure durations (e.g., one-day, 10-day, or lifetime). These non-regulatory levels are intended to help states, water suppliers, and others address contaminants for which federal (or state) drinking water standards have not been established. Some states may use health advisories to inform their own state-specific drinking water regulations. Health advisories may be used to address various circumstances: to provide interim guidance while EPA evaluates a contaminant for possible regulation, to provide information for contaminants with limited or localized occurrence that may not warrant regulation, and to address short-term incidents or spills. EPA has issued health advisories for more than 200 contaminants to address different circumstances and subsequently established regulations for many of these contaminants. In May 2016, EPA issued health advisory levels for lifetime exposure to PFOA and PFOS in drinking water. EPA established the Lifetime Health Advisory level for PFOA and PFOS at 70 ppt, separately or combined. In calculating the health advisory level, EPA applied a relative source contribution of 20% (i.e., an assumption that 20% of PFOS and/or PFOA exposure is attributable to drinking water and 80% is from diet, dust, air or other sources). These levels are intended to protect the most sensitive subpopulations (e.g., nursing infants), with a margin of safety, over a lifetime of daily exposure. The Lifetime Health Advisories replaced Provisional Health Advisories that EPA issued in 2009 to address short-term exposures to PFOA and PFOS. SDWA Section 1431 grants EPA "emergency powers" to issue orders to abate an imminent and substantial endangerment to public health from "a contaminant that is present in or is likely to enter a public water system or an underground source of drinking water" and if the appropriate state and local authorities have not acted to protect public health. This authority is available to address both regulated and unregulated contaminants. The EPA Administrator "may take such actions as he may deem necessary" to protect the health of persons who may be affected. Actions may include issuing orders requiring persons who caused or contributed to the endangerment to provide alternative water supplies or to treat contamination. When using this authority, EPA generally coordinates closely with states. EPA reports that it has used its emergency powers under Section 1431 to require responses to PFOA and/or PFOS releases and related contamination of drinking water supplies at four sites, three of which involved the Department of Defense (DOD). Warminster Naval Warfare Center, Pennsylvania. In 2014, EPA issued an administrative enforcement order directing the U.S. Navy to address PFOS in three drinking water supply wells at and near this National Priorities List site. Former Pease Air Force Base, New Hampshire. In August 2015, EPA issued an administrative enforcement order to require the U.S. Air Force to design and construct a system to treat water systems contaminated from releases of PFOA and PFOS at the former Pease Air Force Base in New Hampshire. Horsham Air Guard Station/Willow Grove, Pennsylvania . In 2015, EPA issued an order directing the Air Guard/Air Force to treat onsite drinking water wells and to provide treatment for private offsite wells. Chemours Washington Works Facility , West Virginia/Ohio. EPA issued three emergency orders to this facility in 2002, 2006, and 2009âand amended the 2009 order in 2017 to incorporate the 2016 Lifetime Health Advisory levelârequiring DuPont and Chemours to offer water treatment, connection to a public water system, or bottled water where PFOA concentrations exceeded 70 ppt. In the 116 th Congress, more than 40 bills have been introduced to address PFAS through a broad range of actions and federal agencies. The NDAA for FY2020 (P.L 116-92) and House-passed H.R. 535 include provisions to reduce exposures to PFAS in drinking water and to prevent or remediate the contamination of groundwater, surface water, and drinking water supplies from releases of these substances. This discussion focuses primarily on legislation that amends the Safe Drinking Water Act (SDWA) or otherwise affect public water systems. Table 1 briefly describes relevant provisions of such bills offered in the 116 th Congress. In the context of SDWA, congressional attention has focused primarily on whether EPA might set drinking water standards (MCLs) for PFOA, PFOS, and/or other PFAS. SDWA directs EPA to follow a regulatory development process for contaminants, which includes consideration of technical feasibility and the assessment of health risk reduction benefits and costs, among other factors. On occasion, Congress has directed EPA to promulgate a regulation for a particular contaminant within a specified time frame. Congress has used this approach to prompt EPA to regulate certain contaminants already under review and/or to specify a deadline for issuing regulations under development. In the case of PFAS, representatives of public water systems and others have cautioned against bypassing SDWA's science-based and risk-driven process. As regulatory compliance costs are borne by communities, public water suppliers have urged that regulations be data-driven to better ensure risk reduction benefits. Others have urged "federal leadership" to provide more certainty to states and communities with contaminated water supplies. State drinking water regulators have noted that some states may lack the resources to assess and/or the authority to regulate drinking water contaminants that are not federally regulated, including PFAS. As with certain other contaminants, some states have urged EPA to set national standards. A further concern is that state-by-state actions could create public confusion regarding the safety of drinking water. Enacted December 20, 2019, the NDAA for FY2020 ( P.L. 116-92 ) contain PFAS provisions specific to DOD, EPA, and several other federal agencies. Some NDAA provisions involve the use of aqueous film forming foam, while others address DOD remediation of PFAS-contaminated drinking water, groundwater, and surface water. Among the EPA provisions, the NDAA addresses drinking water as follows: Section 7311 requires EPA to add to UCMR 5 all PFAS or categories of PFAS with validated test methods. Section 7312 amends SDWA to establish a grant program within the Drinking Water State Revolving Fund to assist water systems in addressing emerging contaminants with an emphasis on PFAS. Section 7312 authorizes appropriations of $100 million annually for FY2020-FY2024 for this purpose. On January 10, 2020, the House passed H.R. 535 , a broad PFAS bill. H.R. 535 contains a range of provisions that would address PFAS using multiple authorities, including several EPA-administered laws. Regarding drinking water, the bill includes several specific provisions, some of which would amend SDWA: Section 5 would amend SDWA to require EPA, within two years of enactment, to promulgate a national primary drinking water regulation for PFAS with standards for PFOA and PFOS at a minimum. It would establish a separate regulatory process for PFAS to accelerate EPA's promulgation of drinking water standards. Among other provisions, this section would require EPA to propose a regulation for a PFAS within 18 months (rather than 24 months) of making a determination to regulate it. This section would allow EPA, when developing regulations, to rely on health risk information for one PFAS to make reasoned extrapolations regarding the health risks of other PFAS. It would also direct EPA to issue a health advisory within a year of finalizing a toxicity value for a single PFAS or class of PFAS. Section 6 would prohibit EPA (but not states) from imposing penalties for violations of PFAS drinking water regulations until five years after the date of promulgation (to allow systems time to make capital improvements as needed for compliance). Section 7 would add SDWA Section 1459E to direct EPA to establish a competitive grant program to assist community water systems with installing treatment technologies to address PFAS contamination. To support this program, Section 7 would authorize annual appropriations of $125 million for FY2020 and FY2021 and $100 million for FY2022-FY2024. EPA would be required to give funding priority to community water systems that (1) serve a "disadvantaged community or a disproportionately exposed community," (2) provide at-least a 10% cost share, or (3) demonstrate the capacity to maintain the treatment technology. Other bills introduced in the 116 th Congress would variously require EPA to establish an MCL for specific PFAS or for PFAS as a group. These include S. 1507 (as reported), S. 1473 , and H.R. 2377 . Additionally, S. 1507 and H.R. 2800 would require public water systems to conduct monitoring for more PFAS in drinking water. Several billsâincluding S. 1507 , H.R. 2533 / H.R. 2741 (Title II), and H.R. 1417 / S. 611 âwould authorize grants for public water systems and/or households to treat PFAS in drinking water. In contrast, H.R. 2570 would direct EPA to establish PFAS manufacturing fees to support the "PFAS Treatment Trust Fund." Amounts in the trust fund would be available to EPA, without further appropriation, to make grants to community water systems and municipal wastewater treatment works for costs associated with PFAS removal.

Summary: Per- and polyfluoroalkyl substances (PFAS) are fluorinated chemicals that have been used in an array of commercial, industrial, and U.S. military applications for decades. Some of the more common applications include nonstick coatings, food wrappers, waterproof materials, and fire suppressants. Detections of some PFAS in drinking water supplies and uncertainty about potential health effects associated with exposure to particular PFAS above certain concentrations have increased calls for the U.S. Environmental Protection Agency (EPA) to address these substances in public water supplies. For those few PFAS for which scientific information is available, animal studies suggest that exposure to particular substances above certain levels may be linked to various health effects, including developmental effects; changes in liver, immune, and thyroid function; and increased risk of some cancers. In 2009, EPA listed certain PFAS for formal evaluation under the Safe Drinking Water Act (SDWA) to determine whether regulations may be warranted. EPA has not issued drinking water regulations for any PFAS but has taken various actions to address PFAS contamination. In the 116 th Congress, Members have introduced more than 40 bills to address PFAS through various means. The National Defense Authorization Act (NDAA) for FY2020, P.L. 116-92 , includes multiple PFAS provisions regarding primarily the Department of Defense (DOD), but several involve EPA and other federal agencies. Among the EPA provisions, Title LXXIII, Subtitle A, directs EPA to require public water systems to conduct additional monitoring for PFAS and creates a grant program for public water systems to address PFAS and other emerging contaminants. The House of Representatives passed H.R. 535 , a broad PFAS bill, on January 10, 2020. Among SDWA provisions, H.R. 535 would direct EPA to issue drinking water regulations for at least two PFAS within two years and establish a separate standard-setting process for PFAS. In February 2019, EPA released its PFAS Action Plan, which discusses the agency's current and proposed actions to address these substances under its various statutory authorities. Regarding SDWA, the plan notes that EPA is following the statutory process for evaluating PFASâparticularly perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)âto determine whether national primary drinking water regulations are warranted. The Fall 2019 Regulatory Agenda indicated that EPA planned to propose preliminary regulatory determinations for PFOA and PFOS by the end of 2019 and finalize determinations by January 2021. The absence of a national health-based drinking water standard for any PFAS has increased interest in the SDWA process for regulating contaminants. The statute prescribes a risk- and science-based process for evaluating and regulating contaminants in drinking water. The evaluation process includes identifying contaminants of potential concern, assessing health risks, collecting occurrence data (and developing reliable analytical methods necessary to do so), and making determinations as to whether a national drinking water regulation is warranted for a contaminant. PFAS include thousands of diverse chemicals, and setting drinking water standards for individual or groups of PFAS raises technical and scientific challenges. For example, SDWA requires EPA to make determinations and set standards using the best available peer-reviewed science and occurrence data. However, data on the potential health effects and occurrence are available for few of these substances. Further, EPA may face challenges in developing test methods and identifying treatment technologies for a diverse array of PFAS. Contamination of drinking water by PFAS can pose challenges for states and communities, and some have called for EPA to establish enforceable standards. State drinking water regulators have noted that many states may face significant obstacles in setting their own standards. For contaminants not regulated under SDWA, EPA is authorized to issue non-enforceable health advisories, which provide information on health effects, testing methods, and treatment techniques for contaminants of concern. In 2016, EPA established health advisory levels for PFOA and PFOS in drinking water at 70 parts per trillion (separately or combined). SDWA also authorizes EPA to take actions it deems necessary to abate an imminent and substantial endangerment to public health from a contaminant present in or likely to enter a public water system or an underground source of drinking water. Actions may include issuing orders requiring persons who caused or contributed to the endangerment to provide alternative water supplies or to treat contamination. Since 2002, EPA has used this authority to require responses to PFOA and/or PFOS contamination of water supplies associated with four sites, including three DOD sites.