29, 2021 Clean Water Act Laura Gatz Recent decades have seen increased national attention to the presence of "emerging contaminants" or " Analyst in Environmental or contaminants of emerging concern" (CECs) in surface water and groundwater. Although there Policy is no federal statutory or regulatory definition of CECs, generally, the term generally refers to unregulated substances detected in the environment that may present a risk to human health, aquatic life, or the environment, and for which the scientific understanding of potential risks is evolving. CECs can include many different types of manufactured chemicals and substances—such as those in (e.g., pharmaceuticals, industrial chemicals, agricultural products, and microplastics—) as well as naturally occurring substances, such as (e.g., algal toxins). . Data on CECs that would help determine their risk to humans and, aquatic life, or or other aspects of the environment are often limited. Increased monitoring and detections of one particular group of chemicals, per- and polyfluoroalkyl substances (PFAS), has recently heightened public and congressional interest in these CECs and has also prompted a broader discussion about how CECs are identified, detected, and regulated and whether additional actions should be taken to protect human health and the environment. While several statutes provide authorities to the U.S. Environmental Protection Agency (EPA) and states to address CECs, this report examines authorities available under the Clean Water Act (CWA)—which Congress established to restore and protect the quality of the nation'’s surface waters.

EPA has several CWA authorities it may use to address CECs, although it faces some challenges in doing so. Under the CWA, a primary mechanism to control contaminants in surface waters is through permits. The statute prohibits the discharge of pollutants from any point source (i.e., a discrete conveyance) to waters of the United States without a permit. The CWA authorizes EPA and states to limit or prohibit discharges of pollutants in the National Pollutant Discharge Elimination System (NPDES) permits they issue. These permits incorporate technology-based and water-quality-based requirements.

The CWA authorizes EPA and states to address CECs through technology-based effluent limitations using national Effluent Limitation Guidelines and Standards (ELGs) or by setting technology-based effluent limits in NPDES permits on a case-by-case basis. The CWA requires EPA to publish ELGs, which are the required minimum standards for industrial wastewater discharges. The CWA also requires EPA to annually review all existing ELGs and to publish a biennial plan that includes a schedule for review and revision of promulgatedexisting ELGs, identifies categories of sources discharging toxic or nonconventional pollutants that do not have ELGs, and establishes a schedule for promulgating ELGs for any newly identified categories. In cases where EPA has not established an ELG for a particular industrial category or type of facility, or where pollutants or processes were not considered when an ELG was developed, the permitting authority (EPA or states) may still impose The CWA also authorizes EPA and states to use certain NPDES permit authorities to manage CECs, such as imposing technology-based effluent limits on a case-by-case basis. Although EPA and states have these authorities available to address CECs, there are some challenges to doing so, including a lack of data available to support new ELGs or updates to existing ELGs. Agency officials stated that it is difficult for the agency to keep pace with the growth of new chemicals in commerce.

The CWA also authorizes EPA and states to address CECs through water-quality-based requirements. States are required to adopt water quality standards for waters of the United States and review them at least once every three yearsor revised ELGs. The CWA also authorizes EPA and states to address CECs through water-quality-based requirements. The CWA requires EPA to publish, and "“from time to time thereafter revise"” water quality criteria that reflect the latest scientific knowledge. States use EPA's criteria as guidance in developing their water quality standards. The CWA directs states to adopt criteria to protect their water bodies' designated uses and to also adopt criteria for all pollutants on the Toxic Pollutant List, for which EPA has published criteria. Once a state adopts water quality criteria for a contaminant as part of its water quality standards, several CWA tools are available to the state for achieving them. The primary tool is to establish water-quality-based effluent limitations in NPDES These criteria are recommendations to states and tribal governments for use in developing their own water quality standards, which they use to protect and restore waters and to inform water-quality-based effluent limits in permits. Although EPA and states have authority to address CECs through water-quality-based requirements, they often lack data needed to support development of criteria or water-quality-based effluent limitations.

The CWA also authorizes EPA to designate contaminants as toxic pollutants or as hazardous substances, which may trigger other actions under the CWA and the Comprehensive Environmental Response, Compensation, and Liability Act.

Recent congressional interest in CECs has largely focused on addressing one particular group of CECs—PFAS—and on addressing them through otherseveral statutes. In the 117th Congress, the House Subcommittee on Water Resources and Environment held a hearing focused on CECs and the CWA’s framework for addressing them in surface waters. Some Members have also introduced bills that propose to address PFAS or other CECs using CWA authorities. In addition, Congress passed the Infrastructure Investment and Jobs Act (P.L. 117-58), which provides $1 billion over five fiscal years through the Clean Water State Revolving Fund to address emerging contaminants in wastewater treatment plants. Congressional Research Service link to page 4 link to page 5 link to page 6 link to page 8 link to page 11 link to page 13 link to page 15 link to page 16 link to page 18 link to page 18 link to page 20 link to page 20 link to page 20 link to page 21 link to page 22 link to page 23 link to page 8 link to page 8 link to page 24 Contaminants of Emerging Concern Under the Clean Water Act Contents Introduction ..................................................................................................................................... 1 Addressing CECs Through the Clean Water Act ............................................................................. 2 Technology-Based Requirements .............................................................................................. 3 Effluent Limitation Guidelines and Standards (ELGs) ....................................................... 5 Options to Address CECs Through Technology-Based Requirements ............................... 8 Challenges to Addressing CECs Through Technology-Based Requirements ................... 10 Water-Quality-Based Requirements ........................................................................................ 12 Water Quality Criteria ....................................................................................................... 13 Options to Address CECs Through Water-Quality-Based Requirements ......................... 15 Challenges to Addressing CECs Through Water-Quality-Based Requirements ............... 15 Designating CECs as Toxic Pollutants or Hazardous Substances ........................................... 17 Toxic Pollutants—CWA Section 307 ................................................................................ 17 Hazardous Substances—CWA Section 311 ...................................................................... 17 Implications of CWA Designations on CERCLA ............................................................. 18 Legislation in the 117th Congress .................................................................................................. 19 Conclusion ..................................................................................................................................... 21 Figures Figure 1. Clean Water Act Technology Levels of Control Required for Non-POTW Dischargers by Pollutant Category ............................................................................................... 5 Contacts Author Information ........................................................................................................................ 21 Congressional Research Service Contaminants of Emerging Concern Under the Clean Water Act Introduction statutes. However, in the 116^th Congress, H.R. 3616 and H.Amdt. 537, Section 330A, of the House-passed version of the National Defense Authorization Act for FY2020 (H.R. 2500), would direct EPA to add PFAS to the CWA Toxic Pollutant List and publish ELGs that establish effluent limitations and standards for PFAS within specified time frames.

Over the past couple of decades, national attention to "“emerging contaminants"” or "“contaminants of emerging concern"” (CECs) in surface water and groundwater has been increasing. Although there is no federal statutorystatutory or regulatory definition of CECs, generally, the term refers to unregulated substances detected in the environment that may present a risk to human health, aquatic life, or the environment. CECs can include many different types of manmade chemicals and substances—such as those in personal care products, pharmaceuticals, industrial chemicals, lawn care and agricultural products, and microplastics—as well as naturally occurring substances such as algal toxins or manganese.

CECs often enter the environment, including ground and surface waters, via municipal and industrial wastewater discharges and urban and agricultural storm runoff. Although municipal and industrial wastewater are both treated prior to discharge into waterways, treatment facilities are often not designed to remove CECs. The availability of data on CECs—such as concentration and pervasiveness in the environment or exposure or toxicity data that would help determine their risk to humans and aquatic life—may be limited.

In some cases, detections of CECs in the environment have triggered a call for action from federal, state, and local government, as well as Congress. Increased monitoring and detections of one particular group of chemicals, per- and polyfluoroalkyl substances (PFAS), has recently heightened public and congressional interest in these CECs and has also prompted a broader discussion about how CECs are identified, detected, and regulated and whether additional actions should be taken to protect human health and the environment.¹

1 Several statutes—including the Safe Drinking Water Act;²2 the Toxic Substances Control Act (TSCA);³3 the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA);⁴4 and the Clean Water Act (CWA)⁵5—provide authorities to the U.S. Environmental Protection Agency (EPA) and states to address particular CECs. In the 116^th117th Congress, Members have introduced more than 4050 bills to address PFAS through various means. Multiple bills, including House- and Senate-passed National Defense Authorization Act (NDAA) bills for FY2020 (H.R. 2500 and S. 1790, respectively), would direct EPA to take regulatory and other actions to address PFAS under several environmental statutes. Two of these bills (H.R. 2500 and H.R. 3616) would direct EPA to take regulatory and other actions to address PFAS under several environmental statutes. Several bills, such as the PFAS Action Act of 2021 (H.R. 2467) and the Clean Water Standards for PFAS Act of 2021 (H.R. 3622 and S. 1907), would direct EPA to address PFAS using authorities provided to the agency under the CWA, which Congress established to restore and protect the quality of the nation'’s surface waters.

Global concern about another group of CECs—microplastics—and their potential impacts has also been mounting.⁶ Recent studies6 Studies have found that treated effluents from wastewater treatment plants 1 See CRS Report R45793, PFAS and Drinking Water: Selected EPA and Congressional Actions, by Elena H. Humphreys, for an overview of EPA’s ongoing and proposed actions to address PFAS under Safe Drinking Water Act authorities. See also CRS Report R45986, Federal Role in Responding to Potential Risks of Per- and Polyfluoroalkyl Substances (PFAS), coordinated by David M. Bearden. 2 42 U.S.C. §300f-300j. 3 15 U.S.C. §2601 et seq. 4 42 U.S.C. §9601 et seq. 5 33 U.S.C. §1251 et seq. 6 While researchers and the government have been working to address plastic pollution for decades, more recently, the accumulation and potential impacts of plastic pollution have become an emerging issue. Recent studies have shown that microplastics (i.e., plastic particles less than 5 millimeters in size in any one dimension) are widespread in marine and freshwater ecosystems and may also have negative ecological impacts. See EPA, State of the Science White Paper: Congressional Research Service 1 Contaminants of Emerging Concern Under the Clean Water Act have found that treated effluents from wastewater treatment plants can be key sources of microplastics, as can runoff from agricultural sites where sewage sludge from the wastewater treatment process has been applied as fertilizer.⁷7 As with many other CECs, wastewater treatment facilities are generally not designed to screen for microplastic debris, such as microbeads, plastic fragments, or plastic fibers from clothing. Congress has shown interest in addressing the impacts of plastic pollution. In 2015, Congress passed legislation to ban plastic microbeads from rinse-off personal care products ("Microbead-Free Waters Act of 2015," ; P.L. 114-114). More recently, some Members in the 116^th Congress announced plans to introduce comprehensive legislation to address plastic waste in fall 2019.⁸

114). In the 117th Congress, some Members have introduced legislation to address plastic waste, including both broad efforts to address plastic and microplastic through several statutes as well as legislation focused specifically on efforts to address microplastics through authorities provided under the CWA. In addition, the Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58) provides $1 billion over five fiscal years for the primary financial assistance program that supports wastewater infrastructure—the Clean Water State Revolving Fund program, authorized by the CWA—for a range of projects to address emerging contaminants.8 Some stakeholders have asserted that EPA could be more effective in using its existing CWA authorities to address CECs, while others have suggested a need to identify and address potential gaps in CWA authorities through amendments to the statute.⁹9 This report examines authorities available to address CECs under the CWA.

Addressing CECs throughThrough the Clean Water Act

EPA has several CWA authorities it may use to address CECs, although it faces some challenges in doing so. The CWA'’s stated objective is "“to restore and maintain the chemical, physical, and biological integrity of the Nation'’s waters."¹⁰”10 To help achieve this objective, the CWA prohibits the discharge of pollutants from any point source (i.ee.g., a discrete conveyance, such as a pipe, ditch, etc.) to waters of the United States without a permit.¹¹11 Under the CWA, one of the primary mechanisms to protect or improve surface water quality is to limit or prohibit discharges of contaminants, including CECs, in National Pollutant Discharge Elimination System (NPDES) permits.¹²12 The CWA authorizes EPA and delegated states to set limits or prohibit discharges of A Summary of Literature on the Chemical Toxicity of Plastics Pollution to Aquatic Life and Aquatic-Dependent Wildlife, December 2016, https://www.epa.gov/trash-free-waters/epa-reports#wp. Also see EPA Office of Wetlands, Oceans and Watersheds, Microplastics Expert Workshop Report, December 2017, https://www.epa.gov/sites/production/files/2018-03/documents/microplastics_expert_workshop_report_final_12-4-17.pdf. 7 EPA, State of the Science White Paper. See also Paul Kay et al., “Wastewater Treatment Plants as a Source of Microplastics in River Catchments,” Environmental Science and Pollution Research, vol. 25, no. 20 (July 2018), pp. 20264-20267. 8 For additional discussion, see CRS Report R46892, Infrastructure Investment and Jobs Act: Drinking Water and Wastewater Infrastructure, by Elena H. Humphreys and Jonathan L. Ramseur. 9 Association of Clean Water Administrators (ACWA) and Association of State Drinking Water Administrators (ASDWA), Recommendations Report—Contaminants of Emerging Concern Workgroup, May 2019, https://www.asdwa.org/wp-content/uploads/2019/05/ASDWA-ACWA-Report-on-Contaminants-of-Emerging-Concern-2019.pdf, p. 9. 10 CWA §101(a); 33 U.S.C. §1251(a). 11 CWA §301; 33 U.S.C. §1311. Point source is defined at CWA §502(14); 33 U.S.C. §1362(14). 12 33 U.S.C. §1342. Under CWA Section 402, states and EPA issue NPDES permits to municipal and nonmunicipal point sources to authorize their discharges. Note that 47 states are authorized to administer their own NPDES permits. EPA administers NPDES permits in Massachusetts, New Hampshire, New Mexico, the District of Columbia, and certain territories and Indian lands. Per CWA Section 502(3) (33 U.S.C. §1362(3)), state is defined to include a state, the District of Columbia, or any of the U.S. territories. Per CWA Section 518 (33 U.S.C. §1377), EPA is authorized to Congressional Research Service 2 Contaminants of Emerging Concern Under the Clean Water Act The CWA authorizes EPA and delegated states to set limits or prohibit discharges of pollutants in permits through technology-based effluent (i.e., discharge) limitations and standards and through water-quality-based effluent limitations, which are established through water quality standards and criteria. Technology-based effluent limitations are specific numerical limits (i.e., maximum allowable levels of specific pollutants) that represent the minimum level of control that must be established in a permit.¹³13 In cases where technology-based effluent limitations are not adequate to meet applicable water quality standards, the permits also incorporate water-quality-based effluent limitations.¹⁴14 Water-quality-based effluent limitations are specific limits established in a permit that, if not exceeded in the discharge, allow for attainment of water quality standards in the receiving water.¹⁵15 Water quality standards—established by states, territories, tribes, and EPA—define the desired condition or level of protection of a water body and what is needed to achieve or protect that condition.¹⁶16 In addition, the CWA authorizes EPA to designate contaminants as toxic pollutants (CWA §307) or as hazardous substances (CWA §311), which may trigger other actions under the CWA and CERCLA.¹⁷17 This section first identifies the authorities available under the CWA, their applicability to CECs, and potential challenges with EPA use of these authorities.

Technology-Based Requirements

The CWA requires EPA to establish technology-based effluent limitations for various categories of point sources/dischargers.¹⁸ .18 Technology-based requirements consider the performance of specific technologies as well as economic achievability. TheseThese limits do not specify what technologies must be employed; rather,, they establish the levels of specific pollutants that are allowable in the discharge based on the performance of technologies identified as representing specified levels of control (e.g., best available technology economically achievable, best conventional pollutant control technology). CWA Section 301 prescribes the levels of control required. EPA broadly classifies NPDES permittees as either (1) publicly owned treatment works (POTWs)¹⁹19 or (2) non-POTWs, which include all other point sources and are also often called nonmunicipalnonmunicipal facilities or industrial facilities.²⁰

The CWA requires POTWs .20 treat an Indian tribe as a state for certain sections of the CWA, including the sections pertaining to CWA permitting. 13 CWA §301(b); 33 U.S.C. §1311(b); 40 C.F.R. §125.3. 14 40 C.F.R. §122.44(d). 15 40 C.F.R. §122.44(d). Water-quality-based effluent limitations apply at the point of discharge, such as the end of the outfall pipe discharging into a water body. 16 40 C.F.R. §131.3(i)-(j). Water quality standards apply throughout the water body and reflect the maximum levels of specific pollutants that can be present in a water body and still allow that water body to meet its designated use. 17 33 U.S.C. §1317; 33 U.S.C. §1321. Such designations also trigger hazardous substance designations (and liability) under CERCLA. 18 CWA §301(b); 33 U.S.C. §1311(b); CWA §304(b); 33 U.S.C. §1314(b); CWA §306; 33 U.S.C. §1316; CWA §307; 33 U.S.C. §1317. 19 Per 40 C.F.R. §403.3(q), a POTW is a treatment works as defined by CWA Section 212, which is owned by a state or municipality (as defined by CWA Section 502(4)). The definition includes any devices and systems used in the storage, treatment, recycling, and reclamation of municipal sewage or industrial wastes of a liquid nature. It also includes sewers, pipes, and other conveyances only if they convey wastewater to a POTW. The term also means the municipality that has jurisdiction over the indirect discharges to and the discharges from the treatment works. 20 Non-POTWs include other point sources, such as industrial and commercial facilities, industrial stormwater, concentrated animal feeding operations, and vessel discharges. Federal facilities fall under the non-POTW source category. EPA, NPDES Permit Writers’ Manual, 2010, https://www.epa.gov/sites/production/files/2015-09/documents/pwm_2010.pdf. Congressional Research Service 3 link to page 8 Contaminants of Emerging Concern Under the Clean Water Act The CWA requires POTWs to meet secondary treatment standards as determined by EPA.21 to meet secondary treatment standards as determined by EPA.²¹ Secondary standards are based on performance data for POTWs that use physical and biological treatment to remove or control conventional pollutants.²²

22 As shown inin Figure 1, the CWA requires non-POTW dischargers to achieve specified levels of control based on (1) whether a discharger directly or indirectly discharges into a water of the United States (an indirect discharger discharges to a POTW for treatment prior to discharge into a water of the United States), (2) whether the discharger is a new or existing source, and (3) the category of pollutant (conventional, toxic,²³ or nonconventional²⁴).²⁵

23 or nonconventional24).25 21 CWA §301(b)(1)(B); 33 U.S.C. §1311(b)(1)(B). As directed by CWA Section 304(d)(1), EPA promulgated secondary treatment standards for biochemical oxygen demand, total suspended solids, and pH. See 40 C.F.R. §133 for secondary treatment standards. The CWA and federal regulations allow adjustments to secondary treatment requirements for biochemical oxygen demand and total suspended solids for equivalent to secondary facilities, per 40 C.F.R. §133.105. 22 Conventional pollutants include biochemical oxygen demand, total suspended solids, fecal coliform, pH, and oil and grease. CWA Section 304(a)(4) designates biological oxygen demand, suspended solids, fecal coliform, and pH as conventional pollutants. It also authorizes EPA to revise the list of conventional pollutants from time to time. EPA designated oil and grease as an additional conventional pollutant in 1979 (EPA, “Identification of Conventional Pollutants,” 44 Federal Register 44501, 1979). The list of conventional pollutants is codified at 40 C.F.R. §401.16. 23 Toxic pollutant includes the 65 pollutants and classes of pollutants on EPA’s Toxic Pollutant List. Section 307(a)(1) (33 U.S.C. §1317(a)(1)) directed EPA to adopt an initial list of toxic pollutants presented in Committee Print 95-30 of the House Committee on Public Works and Transportation (U.S. Congress, House Committee on Public Works and Transportation, Data Relating to H.R. 3199 (Clean Water Act of 1977), committee print, 95th Cong., November 1977, H.Prt. 95-30 [Washington: GPO, 1977], pp. 3-4). This list included both individual chemicals and categories of chemical compounds. As presented in the legislative history, this initial list was negotiated between EPA and the Natural Resources Defense Council in Natural Resources Defense Council v Train (U.S. Congress, House Committee on Public Works and Transportation, Subcommittee on Investigations and Review, Water Contamination by Toxic Pollutants: An Assessment of Regulation, committee print, 95th Cong., September 1977, 95-26, p. 6). The Toxic Pollutant List is codified at 40 C.F.R. §401.15. In 1977, EPA developed the Priority Pollutant List to make Toxic Pollutant List implementation more practical for water testing and regulatory purposes. The Priority Pollutant List includes individual chemicals, rather than groups of pollutants, for which EPA has published analytical test methods. Originally, the list included 129 pollutants. In 1981, when three pollutants were removed from the Toxic Pollutant List, they were also removed from the Priority Pollutant List. Accordingly, the Priority Pollutant List, codified at 40 C.F.R. §423, Appendix A, currently contains 126 pollutants. 24 Nonconventional pollutant includes any pollutants other than those identified as conventional or toxic pollutants. 25 CWA §301(b); 33 U.S.C. §1311(b); CWA §304(b); 33 U.S.C. §1314(b); CWA §306; 33 U.S.C. §1316; CWA §307; 33 U.S.C. §1317. Congressional Research Service 4 Contaminants of Emerging Concern Under the Clean Water Act Figure 1. Clean Water Act Technology Levels of Control Required for Non-POTW Figure 1. Clean Water Act Technology Levels of Control Required for Non-POTW Dischargers by Pollutant Category

Source: CRS, based on CWA §§301, 304, 306, and 307. Notes Notes: EPA regulations define new source as "“any building, structure, facility, or installation from which there is or may be a '‘discharge of pollutants,'pol utants,’ the construction of which commenced: (a) after promulgation of standards of performance under CWA sectionSection 306 which are applicable to such source, or (b) after proposal of standards of performance in accordance with sectionSection 306 of CWA which are applicable to such source, but only if the standards are promulgated in accordance with section 306 within 120 days of their proposal"” (40 C.F.R. §122.2). An existing source is any source that is not a new source or a new discharger (40 C.F.R. §122.29 (a)(3)).

Effluent Limitation Guidelines and Standards (ELGs)

The CWA requires EPA to publish national regulations for non-POTW dischargers—called Effluent Limitation Guidelines and Standards (ELGs)—which set minimum standards for specific pollutants in industrial wastewater discharges based on the specified levels of control.²⁶26 Since 1972, EPA has developed ELGs for 59 industrial categories.²⁷27 For direct dischargers, states or EPA incorporate the limits established in ELGs into the NPDES permits they issue. For indirect dischargers, pretreatment standards established in ELGs to prevent pass through and interference at the POTW apply.²⁸

28 26 CWA §304(b); 33 U.S.C. §1314(b); CWA §306(b); 33 U.S.C. §1316(b); CWA §307(b)-(c); 33 U.S.C. §1317(b)-(c). 27 40 C.F.R. Chapter 1, Subchapter N, “Effluent Guidelines and Standards.” See also EPA, “Industrial Effluent Guidelines,” https://www.epa.gov/eg/industrial-effluent-guidelines. 28 The national pretreatment program is a component of the NPDES program, which involves federal, state, and local regulatory agencies. Local municipalities are mostly responsible for implementing and enforcing pretreatment requirements. EPA and states authorized to act as the approval authority for POTWs in their states may approve a POTW’s pretreatment program. If approved, the POTW is the control authority responsible for ensuring compliance Congressional Research Service 5 Contaminants of Emerging Concern Under the Clean Water Act The CWA requires EPA to annually review all existing ELGs to determine whether revisions are appropriate.²⁹29 In addition, CWA Section 304(m) requires EPA to publish a plan every two years that includes a schedule for review and revision of promulgated ELGs, identifies categories of sources discharging toxic or nonconventional pollutants that do not have ELGs, and establishes a schedule for promulgating ELGs for any newly identified categories.³⁰

30 In its 2002 draft Strategy for National Clean Water Industrial Regulations, EPA described a process for identifying existing ELGs that the agency should consider revising as well as industrial categories that may warrant development of new ELGs.³¹31 As outlined in the strategy, EPA considers four main factors when prioritizing existing ELGs for possible revision: (1) the amount and type of pollutants in an industrial category'’s discharge and the relative hazard to human health or the environment, (2) the availability of an applicable and demonstrated wastewater treatment technology, process change, or pollution prevention measure that can reduce pollutants in the discharge and the associated risk to human health or the environment; (3) the cost, performance, and affordability or economic achievability of the wastewater treatment technology, process change, or pollution prevention measure; and (4) the opportunity to eliminate inefficiencies or impediments to pollution prevention or technological innovation or promote innovative approaches.³²32 EPA considers nearly identical factors in deciding whether to develop new ELGs.³³

33 EPA uses a variety of screening-level analyses to address these factors. These analyses evaluate discharge monitoring reports and EPA'’s Toxic Release Inventory to rank industrial categories according to the total toxicity of their wastewater.³⁴34 In 2012, the Government Accountability Office recommended that the annual review include additional industrial hazard data sources to augment its screening-level reviews.³⁵35 In response, EPA has begun to use additional data sources that provide information about CECs or new pollutant discharges, industrial process changes, and new and more sensitive analytical methods, among other things. For example, EPA has reviewed data from the agency'’s Office of Pollution Prevention and Toxics to identify potential CECs.³⁶

36 If EPA identifies an industrial discharge category warranting further review, it conducts a more detailed review, which may lead to a new or revised guideline.37 with pretreatment standards. If a POTW does not have an approved pretreatment program, the control authority is the approved state authorized to act as the approval authority or, in unapproved states, the EPA. See 40 C.F.R. §403, “General Pretreatment Regulations for Existing and New Sources of Pollution.” 29 CWA §304(b); 33 U.S.C. §1314(b); CWA §304(g); 33 U.S.C. §1314(g); CWA §304(m)(1)(A); 33 U.S.C. §1314(m)(1)(A). Also, per CWA Section 301(d) (33 U.S.C. §1311(d)), EPA is required to review effluent limitations required by CWA Section 301(b)(2) at least every five years. EPA issues regulations that simultaneously address both of these. 30 33 U.S.C. §1314(m). 31 EPA, A Strategy for National Clean Water Industrial Regulations (Draft), November 2002. 32 EPA, Final 2016 Effluent Guidelines Program Plan, EPA-821-R-18-001, April 2018, https://www.epa.gov/eg/2016-effluent-guidelines-plan-documents. See also EPA, A Strategy for National Clean Water Industrial Regulations, pp. 20-25. 33 EPA, A Strategy for National Clean Water Industrial Regulations, p. 23. 34 EPA, Final 2016 Effluent Guidelines Program Plan, pp. 2-3–2-11. 35 U.S. Government Accountability Office, Water Pollution: EPA Has Improved Its Review of Effluent Guidelines but Could Benefit from More Information on Treatment Technologies, GAO-12-845, September 2012, https://www.gao.gov/products/GAO-12-845. 36 EPA, Final 2016 Effluent Guidelines Program Plan, p. 2-4. 37 EPA, Final 2016 Effluent Guidelines Program Plan, p. 2-5. Congressional Research Service 6 Contaminants of Emerging Concern Under the Clean Water Act EPA’s Recent Biennial Plans EPA’s two most recent biennial plans—the final Effluent Guidelines Program Plan 14 (published in January 2021) and the Preliminary Effluent Guidelines Program Plan 15 (published in September 2021)—have, as required, included details on the agency’s ongoing efforts to determine whether it should update ELGs for several different industrial categories.38 Both of these biennial plans include a focus on the agency’s efforts to determine whether ELGs for several industrial categories should be updated to address PFAS. EPA noted that while there has been significant study in recent years of the presence of PFAS in the environment and in drinking water, there has been relatively little study of the discharges of PFAS to surface water and wastewater treatment facilities.39 Hence, EPA’s recent biennial plans and related actions have included efforts to identify and collect information about PFAS discharges. EPA’s Preliminary Effluent Guidelines Program Plan 14 and EPA’s PFAS Action Plan, both published in October 2019, announced that the agency was beginning a detailed multi-industry study of PFAS use, treatment, and discharge to evaluate if certain industrial sources warranted regulation through ELGs.40 EPA’s final Effluent Guidelines Program Plan 14 provided an update on the PFAS multi-industry study. It also discussed several ongoing regulatory actions, including an advanced notice of proposed rulemaking for the Organic Chemicals, Plastics, and Synthetic Fibers (OCPSF) point source category to solicit information and data about PFAS manufacturers and formulators, which it published in March 2021.41 In September 2021, EPA published its Preliminary Effluent Guidelines Program Plan 15 for public review and comment.42 In this preliminary plan, EPA announced several actions pertaining to PFAS, including a rulemaking to revise the OCPSF category ELGs to address PFAS discharges from PFAS manufacturers; plans to conduct a rulemaking to revise the Metal Finishing ELGs to address PFAS discharges from chromium electroplating facilities; and plans to conduct detailed studies on PFAS in discharges from landfills as well as textile and carpet manufacturers.43 In October 2021, EPA issued its PFAS Strategic Roadmap, which broadened its goals to address PFAS discharges through ELGs, and targeted the end of 2024 as the deadline for “significant progress in its ELG regulatory work.”44 Specifically, EPA established timelines for action on various industrial categories, including nine industrial categories also identified in the proposed “PFAS Action Act of 2021” legislation as well as other industrial categories such as landfills.45 These categories include OCPSF; Pulp, Paper, and Paperboard; Textile Mills; Electroplating; 38 EPA, Effluent Guidelines Program Plan 14, EPA-821-R-21-001, January 2021, https://www.epa.gov/eg/2014-effluent-guidelines-plan-documents. EPA, Preliminary Effluent Guidelines Program Plan 15, EPA-821-R-21-003, September 2021, https://www.epa.gov/eg/preliminary-effluent-guidelines-program-plan. 39 EPA, Effluent Guidelines Program Plan 14, p. 6-3. EPA, Preliminary Effluent Guidelines Program Plan 15, p. 6-3. 40 EPA, EPA’s Per- and Polyfluoroalkyl Substances (PFAS) Action Plan, EPA 823R18004, February 14, 2019, pp. 6, 29-30, https://www.epa.gov/pfas/previous-actions-address-pfas. EPA, Preliminary Effluent Guidelines Program Plan 14, EPA-821-R-19-005, October 2019, https://www.epa.gov/sites/default/files/2019-10/documents/prelim-eg-plan-14_oct-2019.pdf. 41 Effluent Guidelines Program Plan 14. See also EPA, “Clean Water Act Effluent Limitations Guidelines and Standards for the Organic Chemicals, Plastics and Synthetic Fibers Point Source Category,” 86 Federal Register 14560, March 17, 2021. 42 EPA, “Preliminary Effluent Guidelines Program Plan 15,” 86 Federal Register 5115, September 14, 2021. 43 EPA, Effluent Guidelines Program Plan 15. 44 EPA, PFAS Strategic Roadmap: EPA’s Commitments to Action 2021-2024, October 2021, pp. 13-14, https://www.epa.gov/pfas/pfas-strategic-roadmap-epas-commitments-action-2021-2024. 45 Ibid; H.R. 2467, §17. Congressional Research Service 7 Contaminants of Emerging Concern Under the Clean Water Act Metal Finishing; Leather Tanning and Finishing; Paint Formulating; Electrical and Electronic Components; and Plastics Molding and Forming.46 EPA’s planned actions include47  undertaking rulemakings to restrict PFAS discharges from the industrial categories where EPA has sufficient data to do so (OCPSF, Metal Finishing, and Electroplating categories);48  conducting detailed studies for industrial categories for which EPA has preliminary data, but not enough to determine whether rulemaking is warranted (Electrical and Electronic Components, Textile Mills, and Landfills);49  initiating data reviews for industrial categories for which stakeholders have expressed concern about potential PFAS discharges, but for which there is little known information on such discharges (Leather Tanning and Finishing, Plastics Molding and Forming; and Paint Formulating);50 and  monitoring two industrial categories where the phase out of PFAS is projected by 2024 (Pulp, Paper, and Paperboard and Airports).51 Options to Address CECs Throughdetailed review, which may lead to a new or revised guideline.³⁷

Options to Address CECs through Technology-Based Requirements

Technology-Based Requirements Both EPA and states have authority under the CWA to address CECs through technology-based effluent limitations using ELGs or by setting technology-based effluent limits in NPDES permits on a case-by-case basis. In addition, the CWA authorizes EPA to add contaminants to the Toxic Pollutant List.

ELGs When EPA develops an ELG for a new industrial category or revises an existing ELG, it is for the industrial category—not a specific pollutant. However, as evidenced in the agency's most’s recent effluent guidelines program planplans, EPA may initiate a cross-industry review of particular pollutants (such as the agency is doinghas done with PFAS and nutrients). EPA uses such reviews to prioritize further study of the industrial categories that may be candidates for ELG development or revision to control the discharges of those particular pollutants.³⁹52 If EPA were to determine that new or revised ELGs are warranted to control discharges of those pollutants, and the agency had the necessary data to support the development or revision, the agency could initiate a rulemaking process to do so.

46 H.R. 2467, §17. EPA, PFAS Strategic Roadmap, p. 14. 47 EPA, PFAS Strategic Roadmap, p. 14. 48 EPA anticipates issuing a proposed rule for OCPSF by summer 2023 and for Metal Finishing and Electroplating by summer 2024. The existing ELGs for Electroplating are codified at 40 C.F.R. §413. 49 EPA anticipates these studies to be completed by fall 2022 to inform its decision about a potential rulemaking by the end of 2022. The existing ELGs for Electrical and Electronic Components are codified at 40 C.F.R. §469. 50 EPA aims to complete these studies by winter 2023 to inform its decision about whether sufficient data are available to initiate a potential rulemaking. The existing ELGs for Leather Tanning and Finishing are codified at 40 C.F.R. §425; for Plastics Molding and Forming at 40 C.F.R. §463; and for Paint Formulating at 40 C.F.R. §446. 51 EPA plans to discuss the results of the monitoring and any potential regulatory action in the Final Effluent Limitation Guideline Program Plan 15 in fall 2022. 52 EPA, Final 2016 Effluent Guidelines Program Plan, p. 7-1. Congressional Research Service 8 link to page 13 link to page 13 link to page 20 Contaminants of Emerging Concern Under the Clean Water Act Establishing Technology-Based Effluent Limits in NPDES Permits on a Case-by-Case Basis

and Other NPDES Authorities The CWA also authorizes EPA and states to impose technology-based effluent limits in NPDES permits on a case-by-case basis when "“EPA-promulgated effluent limitations are inapplicable."⁴⁰ ”53 This includes when EPA has not developed ELGs for the industry or type of facility being permitted or pollutants or processes are present that were not considered when the ELG was developed.⁴¹54 This provides a means for the permitting authority to restrict pollutants in a facility's ’s discharge even when an ELG is not available. CWA regulations require best professional judgment to set case-by-case technology-based effluent limits, applying criteria that are similar to the analysis EPA uses to develop ELGs but are performed by the permit writer for a single facility.⁴²

55 The CWA also authorizes permitting authorities (EPA or states) to require facilities with NPDES permits to monitor for certain pollutants or conduct special studies as a means to collect data for future limitation development.56 In addition, the permitting authority may include best management practices in permits to control or abate the discharge of pollutants on a case-by-case basis when “the practices are reasonably necessary ... to carry out the purposes and intent of the CWA.”57 However, the use of some of these authorities may be limited when analytical methods to detect specific pollutants are unavailable. For further discussion, see “Challenges to Addressing CECs Through Technology-Based Requirements.” Toxic Pollutant List Toxic Pollutant List

The CWA also authorizes EPA to designate contaminants as toxic pollutants, which can trigger other actions under the CWA and CERCLA. (For a discussion of the effect of designating a contaminant as a toxic pollutant on the treatment of that contaminant under CERCLA, see "“Designating CECs as Toxic Pollutants or Hazardous Substances.".”) CWA Section 307 authorizes EPA to designate toxic pollutants and promulgate ELGs that establish requirements for those toxic pollutants.⁴³58 Section 307(a)(1) directed EPA to publish a specified list of individual toxic pollutants or combination of pollutants and, from time to time, add or remove any pollutant that possesses certain properties.⁴⁴ 53 CWA §402(a)(1)(B); 33 U.S.C. §1342(a)(1)(B); 40 C.F.R. §125.3(c). 54 EPA, NPDES Permit Writers’ Manual, September 2010, pp. 5-45–5-46, https://www.epa.gov/npdes/npdes-permit-writers-manual. 55 40 C.F.R. §125.3(d). 56 CWA §402(a)(2); 33 U.S.C. §1342(a)(2). EPA, NPDES Permit Writers’ Manual, September 2010, pp. 9-2-9-3, https://www.epa.gov/npdes/npdes-permit-writers-manual. 57 CWA §402(a)(1)-(2). 40 C.F.R. § 122.44(k). 58 33 U.S.C. §1317. Congressional Research Service 9 link to page 8 Contaminants of Emerging Concern Under the Clean Water Act possesses certain properties.59 EPA adopted the initial list of 65 toxic pollutants in 1978, as directed by Congress.⁴⁵60 Since that time, the list of 65 toxic pollutants has generally not changed.⁴⁶

61 Section 307(a)(1) directs EPA to "“take into account the toxicity of the pollutant, its persistence, degradability, the usual or potential presence of the affected organisms in any waters, the importance of the affected organisms, and the nature and extent of the effect of the toxic pollutant on such organisms"” when revising the Toxic Pollutant List.⁴⁷62 Section 307(a)(2) authorizes EPA to develop effluent limitations for any pollutant on the Toxic Pollutant List based on best available technology.⁴⁸63 Notably, however, EPA has the authority to develop effluent limitations for any pollutant regardless of whether it is on the Toxic Pollutant List.

Adding a pollutant to the Toxic Pollutant List would trigger an additional requirement for states. Section 303(c)(2)(B) of the CWA⁴⁹CWA64 requires states, whenever reviewing, revising, or adopting water quality standards, to adopt numeric criteria for all toxic pollutants listed pursuant to Section 307, for which EPA has published water quality criteria under Section 304(a).⁵⁰65 EPA and states use both the ELGs for industrial categories and state water quality standards in establishing pollutant limits in permits under Section 402.⁵¹ (66 (See Figure 1.)

) Challenges to Addressing CECs throughThrough Technology-Based Requirements

EPA and states face a number of challenges in addressing CECs through technology-based effluent limitations. In particular, EPA officials stated that in developing a new ELG or updating an existing ELG, the agency needs to gather extensive supporting information.⁵²67 This effort includes identifying the pollutants of concern; evaluating the levels, prevalence, and sources of those pollutants of concern; determining whether the pollutants are in treatable quantities and 59 33 U.S.C. §1317(a)(1). Section 307(a)(1) directed EPA to adopt an initial list of 65 toxic pollutants presented in Committee Print 95-30 of the House Committee on Public Works and Transportation. (U.S. Congress, House Committee on Public Works and Transportation, Data Relating to H.R. 3199 (Clean Water Act of 1977), committee print, 95th Cong., November 1977, H.Prt. 95-30 [Washington: GPO, 1977], pp. 3-4.) These pollutants included both individual chemicals and categories of chemical compounds. As presented in the legislative history, this initial list was negotiated among parties to a 1976 settlement agreement between EPA and the Natural Resources Defense Council in the case of Natural Resources Defense Council v Train (U.S. Congress, House Committee on Public Works and Transportation, Subcommittee on Investigations and Review, Water Contamination by Toxic Pollutants: An Assessment of Regulation, committee print, 95th Cong., September 1977, 95-26, p. 6). 60 EPA, “Publication of Toxic Pollutant List,” 43 Federal Register 4108, January 31, 1978. 61 EPA removed three pollutants from the list in 1981 after determining that the chemical properties of the pollutants are such that they do not pose a risk to human health or the environment by exposure through water. However, delisting these three pollutants did not change the 65 entries on the Toxic Pollutant List because they were specific compounds listed within two broader categories of listed compounds—halomethanes and haloethers. (See EPA, “Removal of Dichlorodifluoromethane and Trichlorofluoromethane from the Toxic Pollutant List Under Section 307(a)(1) of the Clean Water Act,” 46 Federal Register 2266, January 8, 1981; EPA, “Removal of Bis-(Chloromethyl) Ether (BCME) from the Toxic Pollutant List Under Section 307(a)(1) of the Clean Water Act,” 46 Federal Register 10723, February 4, 1981.) The Toxic Pollutant List is codified in federal regulation at 40 C.F.R. §401.15. 62 33 U.S.C. §1317(a)(1). 63 33 U.S.C. §1317(a)(2). 64 33 U.S.C. §1313(c)(2)(B). 65 33 U.S.C. §1314(a). 66 33 U.S.C. §1342. 67 Personal communication between CRS and EPA staff, August 6, 2019. Congressional Research Service 10 Contaminants of Emerging Concern Under the Clean Water Act those pollutants of concern; determining whether the pollutants are in treatable quantities and whether effective treatment technologies are available; and developing economic data to project the cost of treatment, among other things.⁵³

68 Also, EPA and state officials have asserted that it is difficult for the agency and its CWA programs to keep pace with the growth of new chemicals in commerce.⁵⁴69 Accordingly, the agency is generally reactive rather than proactive in addressing CECs. EPA officials stated that identifying demonstrated treatment technologies and documenting their efficiency is especially challenging.⁵⁵ 70 The officials further stated that the most difficult task is showing that any technology selected as the basis for an ELG is economically achievable for the industry.⁵⁶

71 In addition, EPA and states often lack analytical methods to measure an emerging contaminant.⁵⁷ 72 Even where analytical methods are available, there is still often a lack of data on the levels of the contaminant in dischargers'’ effluent and/or in the receiving surface waters. The two sources of data most readily available to EPA—discharge monitoring report data and toxic release inventory data—are limited to specific contaminants on which industry is required to report.⁵⁸73 EPA stated that the agency'’s capacity to collect data—including obtaining clearance to request and collect the data and undertaking the extensive effort to do so—is limited in light of their staffing levels and resources.⁵⁹

74 Should EPA have enough data to determine that a new or revised ELG is warranted and announce its intent to do so in an effluent guidelines program plan, the time it takes to issue the regulation varies, according to EPA officials. CWA Section 304(m) establishes a three-year time limit for new ELGs.⁶⁰75 For revised ELGs, the EPA officials stated that the time can vary depending upon 68 Personal communication between CRS and EPA staff, August 6, 2019. See also CWA §304(b); 33 U.S.C. §1314(b); and EPA, Final 2016 Effluent Guidelines Program Plan, p. 2-2. 69 Personal communication between CRS and EPA staff, August 6, 2019. See also ACWA, ASDWA, Recommendations Report. 70 Personal communication between CRS and EPA staff, August 6, 2019. 71 Personal communication between CRS and EPA staff, August 6, 2019. 72 For example, in EPA’s PFAS Action Plan, the agency commits in the short term to developing analytical methods to “detect, identify, and quantify” known PFAS of concern in media, including wastewater and groundwater. EPA also commits to developing analytical methods for new, unknown PFAS in the long term. See EPA, Per- and Polyfluoroalkyl Substances (PFAS) Action Plan, February 2019, https://www.epa.gov/sites/production/files/2019-02/documents/pfas_action_plan_021319_508compliant_1.pdf, p. 34. As another example, in 2017, EPA convened a Microplastics Expert Workshop to identify and prioritize the scientific information needed to understand the risks posed by microplastics. In its report summarizing experts’ recommendations, EPA concluded that “development of reliable, reproducible, and high-quality methods for microplastics is fundamental and of utmost importance for understanding microplastics risks.” See EPA, Microplastics Expert Workshop Report. Also, in its Final 2016 Effluent Guidelines Program Plan, EPA describes its ongoing investigation looking at engineered nanomaterials and states that it will continue to look for opportunities to inform current data gaps, including development of analytical methods to detect and quantify engineered nanomaterials. 73 Personal communication between CRS and EPA staff, August 6, 2019. See also EPA, Final 2016 Effluent Guidelines Program Plan, pp. 2-4 and 3-5. 74 Personal communication between CRS and EPA staff, August 6, 2019. See also “As Democrats Push Steep PFAS Deadlines, Regan Seeks More Resources,” InsideEPA, October 6, 2021. Note that under the Paperwork Reduction Act (44 U.S.C. §3501 et seq.), EPA can contact—with a survey or questionnaire—up to nine entities without first obtaining approval from the Office of Management and Budget. If EPA decides to contact 10 or more entities, the act requires the agency to prepare an Information Collection Request. In November 2018, EPA’s Assistant Administrator for the Office of Water issued a memorandum clarifying its processes for collecting information from nine or fewer individuals or entities under CWA Section 308. The memorandum is available at https://www.epa.gov/sites/production/files/2018-11/documents/policy-use-of-cwa-308-letters.pdf. See also “As Democrats Push Steep PFAS Deadlines, Regan Seeks More Resources,” InsideEPA, October 6, 2021. 75 33 U.S.C. §1314(m). Congressional Research Service 11 Contaminants of Emerging Concern Under the Clean Water Act For revised ELGs, the EPA officials stated that the time can vary depending upon the availability of data and the level of complexity—some may be very technical and involve many wastestreams.⁶¹76 Two of the more recently issued ELGs—revisions of the oil and gas extraction and steam electric power generating categories—took five and six years, respectively.⁶²

77 Water-Quality-Based Requirements

Under the CWA, water quality standards translate the goals of the act (e.g., fishable and swimmable waters, no toxic pollutants in toxic amounts) into measurable objectives to protect or improve water quality.⁶³78 States, territories, and authorized tribes (hereinafter referred to collectively as states) are required to adopt water quality standards for waters of the United States, subject to EPA approval.⁶⁴79 They may also adopt standards for additional surface waters if their own state laws allow them to do so.⁶⁵

80 Water quality standards consist of three key required components:⁶⁶

• 1. 81 1. Designated uses for each water body—for example, recreation (swimming or boating), aquatic life support, fish consumption, public water supply, agriculture;
• 2. 2. Criteria, which describe the conditions in a water body necessary to support the designated uses—expressed as concentrations of pollutants or other quantitative measures or narrative statements; and
• 3. 3. An antidegradationAn antidegradation policy for maintaining existing water quality.

States have the primary authority to adopt, review, and revise their water quality standards and implementation procedures. The CWA requires states to review their water quality standards at least once every three years.⁶⁷82 EPA is required to review the states'’ water quality standards.⁶⁸

83 76 Personal communication between CRS and EPA staff, August 6, 2019. 77 Note that these time frames include notice-and-comment requirements under the Administrative Procedure Act. EPA announced its intent to revise the Oil and Gas Extraction ELG to develop pretreatment standards for discharges from unconventional oil and gas facilities to POTWs in 2011 (76 Federal Register 66286) and published its final rule for the Oil and Gas Extraction ELG in 2016 (81 Federal Register 41845). EPA announced its intent to revise the Steam Electric Power Generating ELG in 2009 (74 Federal Register 68603) and issued its final rule in 2015 (80 Federal Register 67838). Note that in November 2019, EPA announced a proposed rule to revise the Steam Electric Power Generating ELG applicable to two of the six wastestreams covered in the 2015 rule and finalized the rule in 2020 (85 Federal Register 64650). On August 3, 2021, EPA announced its decision to initiate a proposed rulemaking to revise the Steam Electric Power Generating ELG “to determine whether more stringent limitations and standards are appropriate and consistent with the technology-forcing statutory scheme and the goals of the CWA.” EPA intends to sign the notice of proposed rulemaking for public comment in the fall of 2022 (86 Federal Register 41801). For more information on the Steam Electric Power Generating ELG, see CRS In Focus IF10778, Overview of the Steam Electric Power Generator Effluent Limitation Guidelines and Standards, by Laura Gatz. 78 Section 101(a) of the CWA (33 U.S.C. §1251(a)) includes the objective and goals of the act. One of the goals—“water quality which provides for the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on the water”—is often referred to in shorthand as “fishable and swimmable waters.” 79 CWA §303(c); 33 U.S.C. §1313(c). Per Section 502(3) of the CWA (33 U.S.C. §1362(3)), state is defined to include a state, the District of Columbia, or any of the U.S. territories. Per Section 518 of the CWA (33 U.S.C. §1377), EPA is authorized to treat an Indian tribe as a state for certain sections of the CWA, including the sections pertaining to water quality standards. EPA regulations at 40 C.F.R. §131.8 lay out the requirements and process by which a tribe may request and be approved to administer its own water quality standards program. 80 CWA §510; 33 U.S.C. §1370. 81 See CWA Section 303(c)(2)(A) for designated uses and criteria and CWA Sections 101(a) and 303(d)(4)(B) for antidegradation. Also see EPA’s implementing regulations at 40 C.F.R. §131. 82 CWA §303(c); 33 U.S.C. §1313(c). 83 If EPA approves the water quality standards, they become effective. If EPA disapproves the water quality standards, Congressional Research Service 12 Contaminants of Emerging Concern Under the Clean Water Act Water Quality Criteria Water Quality Criteria

Water quality criteria prescribe limits on specific contaminants or conditions in a water body that protect particular designated uses of the water body. Both the EPA and states have roles in establishing water quality criteria under CWA Section 304(a) and 303(c)(2), respectively.

EPA Role

CWA Section 304(a) requires EPA to develop and publish and "“from time to time thereafter revise"revise” criteria for water quality that accurately reflect the latest scientific knowledge.⁶⁹84 These criteria are recommendations to states for use in developing their own water quality standards. EPA has developed several different types of criteria, including human health criteria, aquatic life criteria, and recreational criteria.⁷⁰85 EPA has also published guidelines for deriving water quality criteria, which the agency uses to develop new criteria under Section 304(a). These guidelines also serve as guidance to states as they adjust water quality criteria developed under Section 304(a) to reflect local conditions or develop their own scientifically defensible water quality criteria.⁷¹

86 EPA most recently updated its human health criteria in 2015, revising 94 of the 122 existing human health criteria.⁷²87 EPA last updated its methodology for deriving human health criteria in 2000,⁷³88 incorporating "“significant scientific advances in key areas such as cancer and non-cancer risk assessments, exposure assessments, and bioaccumulation in fish."⁷⁴

EPA'”89 EPA’s national recommended aquatic life criteria table currently includes 5859 criteria.⁷⁵90 Many of these criteria were published prior to 1990. In the past 10 years, EPA has published two new criteria.⁷⁶91 EPA has not updated its guidelines for deriving aquatic life criteria since 1985.⁷⁷ 92 According to EPA, however, the guidelines allow for best professional judgment, which they have used in more recent criteria development and updates.⁷⁸93 The agency recognizes that since 1985, the state has 90 days to revise them. If the state does not do so, EPA is required to promulgate standards that meet CWA requirements. CWA §303(c)(3); 33 U.S.C. §1313(c)(3). 84 CWA §304(a)(1); 33 U.S.C. §1314(a)(1). 85 EPA, “Basic Information on Water Quality Criteria,” https://www.epa.gov/wqc/basic-information-water-quality-criteria. 86 EPA, Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health, October 2000, p. iii, https://www.epa.gov/sites/production/files/2018-10/documents/methodology-wqc-protection-hh-2000.pdf; EPA, Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses, 1985, pp. 2-3, https://www.epa.gov/sites/production/files/2016-02/documents/guidelines-water-quality-criteria.pdf. 87 EPA, “Final Updated Ambient Water Quality Criteria for the Protection of Human Health,” 80 Federal Register 36986, June 29, 2015; EPA, “National Recommended Water Quality Criteria—Human Health Criteria Table,” https://www.epa.gov/wqc/national-recommended-water-quality-criteria-human-health-criteria-table. 88 EPA, Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health. 89 EPA, Fact Sheet: Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health—Revised Methodology, 2000, https://www.epa.gov/wqc/fact-sheet-methodology-deriving-ambient-water-quality-criteria-protection-human-health-revised#copy. 90 EPA, “National Recommended Water Quality Criteria—Aquatic Life Criteria Table,” https://www.epa.gov/wqc/national-recommended-water-quality-criteria-aquatic-life-criteria-table. 91 According to personal communication between CRS and EPA staff on May 29, 2019, in the past 10 years, EPA developed new criteria for two substances: carbaryl and acrolein. 92 EPA, Guidelines for Deriving Numerical National Water Quality Criteria. 93 Personal communication between CRS and EPA staff, May 29, 2019. Also see EPA, Guidelines for Deriving Congressional Research Service 13 link to page 18 Contaminants of Emerging Concern Under the Clean Water Act The agency recognizes that since 1985, there has been substantial scientific advancement that warrants updating these guidelines.⁷⁹94 EPA formally initiated the guidelines revision process in 2015. However, according to EPA officials, the agency has shifted its focus from updating the guidelines to determining whether available data and research support development of human health criteria for PFAS.⁸⁰95 In doing so, EPA officials indicated they planplanned to use information gathered for the guidelines revision and also noted that they are not tied to the 1985 guidelines due to the best professional judgment clause included therein.⁸¹

EPA'96 EPA’s recreational water quality criteria are national recommendations for all inland and coastal waters that have a primary contact recreation (i.e., swimming) designated use. EPA establishes recreational water quality criteria to help protect against illness caused by organisms—such as viruses, bacteria, and their associated toxins—in water bodies.⁸²97 In 2012, EPA updated its recreational water quality criteria, which it had last issued in 1986.⁸³98 Additionally, in June 2019, EPA published final recreational water quality criteria for two algal toxins, which are commonly present in harmful algal blooms, to supplement the 2012 recreational water quality criteria.⁸⁴99 In addition, EPA is currently developing recreational water quality criteria for coliphage, a viral indicator of fecal contamination.⁸⁵

100 State Role

States use EPA'’s criteria as guidance in developing their own water quality standards. CWA Section 303(c)(2) requires states to adopt criteria to protect the designated uses of their water bodies and to also adopt criteria for all toxic pollutants listed pursuant to Section 307(a)(1), for which EPA has published criteria under Section 304(a). States'’ water quality criteria must be based on sound scientific rationale, contain sufficient parameters or constituents to protect the designated uses, and support the most sensitive use for water bodies with multiple designated uses.⁸⁶101 EPA regulations further require that states should establish numeric criteria based on CWA Section 304(a) guidance, CWA Section 304(a) guidance modified to reflect site-specific conditions, or other scientifically defensible methods.⁸⁷102 Where numeric criteria cannot be established, states are required to establish narrative criteria or criteria based on biomonitoring methods.⁸⁸ Numerical National Water Quality Criteria, p. 9. 94 EPA, “Aquatic Life Criteria and Methods for Toxics,” https://www.epa.gov/wqc/aquatic-life-criteria-and-methods-toxics#sab. 95 As discussed further under “Challenges to Addressing CECs Through Water-Quality-Based Requirements,” EPA announced in its 2021 PFAS Strategic Roadmap that it will develop national recommended ambient water quality criteria for PFAS to protect aquatic life and human health. 96 Personal communication between CRS and EPA staff, May 29, 2019. 97 EPA, “Recreational Water Quality Criteria and Methods,” https://www.epa.gov/wqc/recreational-water-quality-criteria-and-methods#rec. 98 EPA, 2012 Recreational Water Quality Criteria, December 2012, https://www.epa.gov/sites/production/files/2015-10/documents/rec-factsheet-2012.pdf. 99 EPA, “Recommended Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for Microcystins and Cylindrospermopsin,” 84 Federal Register 26413, June 6, 2019. 100 EPA, “Recreational Water Quality Criteria and Methods,” https://www.epa.gov/wqc/recreational-water-quality-criteria-and-methods#rec. See “Development of Recreational Water Quality Criteria for Coliphage” section. 101 40 C.F.R. §131.11. 102 40 C.F.R. §131.11(b). Congressional Research Service 14 Contaminants of Emerging Concern Under the Clean Water Act methods.103 States may adopt more stringent criteria than what EPA recommends, including for pollutants or parameters for which EPA has not promulgated Section 304(a) criteria.⁸⁹

104 Options to Address CECs throughThrough Water-Quality-Based Requirements

EPA and states may establish water quality criteria for CECs. If EPA were to establish criteria under CWA Section 304(a) for a CEC, that action alone would not necessarily require states to adopt criteria for that contaminant. As explained above, the CWA requires that states adopt criteria to protect their designated uses into their water quality standards. EPA'’s regulations provide that if a state does not adopt new or revised criteria for parameters for which EPA has published new or updated recommendations, then the state shall provide an explanation.⁹⁰105 States are explicitly required, as explained above, to adopt criteria for a contaminant if EPA designates it as a toxic pollutant under CWA Section 307 and publishes criteria for that contaminant under Section 304(a).⁹¹

106 Once a state has adopted water quality criteria for a contaminant as part of its state water quality standards and those standards have been approved, several CWA tools are available for achieving those standards. The primary tool is to limit or prohibit discharges of the contaminant in NPDES permits. In some cases, the technology-based effluent limits may already enable attainment of state water quality standards. In instances where they do not, the permit writer is required to establish water-quality-based effluent limitations.⁹²107 If a water body is not attaining its designated use (i.e., is "impaired"“impaired” for that use), the Total Maximum Daily Load (TMDL) may also be used.⁹³108 A TMDL, essentially a "“pollution diet"” for a water body, is the maximum amount of a pollutant that a water body can receive and still meet water quality standards and an allocation of that amount to the pollutant'’s sources (including a margin of safety).⁹⁴109 TMDLs consider point sources, which can be addressed through permits, as well as nonpoint (diffuse) sources, which are more often addressed through best management practices and related efforts under CWA Section 319 nonpoint source management programs.⁹⁵

110 Challenges to Addressing CECs throughThrough Water-Quality-Based Requirements

A key challenge is often a lack of data about the occurrence, concentration, and persistence of CECs in the environment, as well as the effects on human health and aquatic life. Detection of a contaminant does not necessarily trigger regulatory measures. Information on the potential for the contaminant to adversely affect human health and aquatic life, potential exposure pathways, and other data would also be needed to inform such decisions.

Developing new water quality criteria or updating existing criteria can often be time intensive, particularly in cases where data are limited. The general process for developing criteria involves a 103 40 C.F.R. §131.11(b). 104 CWA §510; 33 U.S.C. §1370. 105 40 C.F.R. §131.20(a). 106 CWA §303(c)(2)(B); 33 U.S.C. §1313(c)(2)(B). 107 Per 40 C.F.R. §122.44(d)(1)(i), limitations must be established in permits to “control all pollutants or pollutant parameters (either conventional, nonconventional, or toxic pollutants) which the Director determines are or may be discharged at a level which will cause, have the reasonable potential to cause, or contribute to an excursion above any State water quality standard, including State narrative criteria for water quality.” 108 CWA §303(d); 33 U.S.C. §1313(d). 109 40 C.F.R. §130.2. 110 33 U.S.C. §1329. Congressional Research Service 15 Contaminants of Emerging Concern Under the Clean Water Act number of steps, including problem formulation and developing an analysis plan; gathering data and analyzing relevant studies; drafting the criteria document; a rigorous review process (e.g., branch level, office level, interagency, and independent external peer review); public notice and comment, and revising and publishing the criteria.⁹⁶111 According to EPA officials, the time it takes to develop or update criteria is often a function of the data that are available.⁹⁷112 EPA officials noted that developing criteria can take several years or longer. For example, the 2016 update for the aquatic life water quality criteria for selenium—an effort characterized by EPA as complicated, in part because of the contaminant'’s bioaccumulative properties—took 10 years to complete.⁹⁸113 In other cases, such as when a contaminant has an existing EPA Integrated Risk Information System value, developing or updating the human health water quality criteria for that contaminant may take less time, according to EPA officials.⁹⁹

114 In May 2019, a report from the Contaminants of Emerging Concern Workgroup, convened by the Association of State Drinking Water Administrators and the Association of Clean Water Administrators, provided recommendations from state regulators regarding the ways state and federal agencies could improve the management of CECs.¹⁰⁰115 The report stated the following:

The use of existing authorities and processes under the CWA and [Safe Drinking Water Act] to establish new criteria or standards is onerous, can take decades to implement, and does not meet public expectations for timely identification and prioritization of CECs…. However slow these federal processes are, many state agencies do not have the infrastructure (i.e., sufficient funds and/or staffing levels), regulatory authority, or However slow these federal processes are, many state agencies do not have the infrastructure (i.e., sufficient funds and/or staffing levels), regulatory authority, or technical expertise to derive their own criteria or set their own standards for drinking water, surface water, groundwater, and fish tissue.

Among numerous other recommendations provided in the report, the CEC workgroup recommended that EPA work with states to generate a list of priority CECs. To that end, EPA officials stated that they are developing a more formalized prioritization process for determining which contaminants warrant criteria development that will incorporate input from multiple stakeholders (including states), leverage information collected under the Safe Drinking Water Act, and incorporate monitoring and other data (e.g., ambient water concentrations).116 In EPA’s 2019 PFAS Action Plan, the agency announced that it was working to determine if available data and research supported the development of CWA Section 304(a) water quality criteria for human health for PFAS.117 In EPA’s October 2021 PFAS Strategic Roadmap, EPA announced that it will develop national recommended ambient water quality criteria for PFAS to 111 Personal communication between CRS and EPA staff, May 29, 2019. 112 Personal communication between CRS and EPA staff, May 29, 2019. 113 Personal communication between CRS and EPA staff, May 29, 2019. See also EPA, Aquatic Life Ambient Water Quality Criterion for Selenium—Freshwater 2016, June 2016, pp. 1-3, https://www.epa.gov/sites/production/files/2016-07/documents/aquatic_life_awqc_for_selenium_-_freshwater_2016.pdf. 114 Personal communication between CRS and EPA staff, May 29, 2019. EPA’s Integrated Risk Information System (IRIS) is a human health assessment program that evaluates information on health effects of exposure to environmental contaminants. For more information on the IRIS program, see EPA, “Integrated Risk Information System,” https://www.epa.gov/iris. According to EPA officials, because development of IRIS values requires a rigorous review process, EPA does not do a separate peer review in developing criteria using an IRIS value (personal communication between CRS and EPA staff, May 29, 2019). 115 ACWA, ASDWA, Recommendations Report. 116 Personal communication between CRS and EPA staff, May 29, 2019. EPA staff stated that, in the past, the agency has more informally determined the need for criteria through state and stakeholder input. 117 EPA, EPA’s Per- and Polyfluoroalkyl Substances (PFAS) Action Plan, pp. 6, 29. Congressional Research Service 16 link to page 12 Contaminants of Emerging Concern Under the Clean Water Act protect aquatic life and human health.118 EPA anticipates by winter 2022 it will publish recommended aquatic life criteria for two PFAS—perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)—and benchmarks for other PFAS for which EPA does not have sufficient data to define a recommended aquatic life criteria value. EPA anticipates publishing human health criteria for PFOA and PFOS by fall 2024.119 Designating CECs as Toxic Pollutants or Hazardous Substances Two sections of the CWA—Sections 307 and 311—authorize EPA to designate contaminants as toxic pollutants and hazardous substances, respectively. Designating a contaminant under Section 307 or Section 311 of the CWA has implications for how the contaminant is treated under CERCLA. CERCLA defines the term hazardous substance to include toxic pollutants designated under CWA Section 307 and hazardous substances designated under CWA Section 311 (as well as substances designated under certain other statutes and other chemicals that EPA may designate as hazardous substances).120 Toxic Pollutants—CWA Section 307 EPA’s authority to designate contaminants under CWA Section 307 as toxic pollutants and the CWA-related implications of that designation are discussed above under “Toxic Pollutant List.” Hazardous Substances—CWA Section 311 CWA Section 311(b)(2)(A) authorizes EPA to promulgate a rule designating as a “hazardous substance” any element or compound that, when discharged as specified under the section, would present an imminent and substantial danger to public health or welfare, including but not limited to fish, shellfish, wildlife, shorelines, and beaches.121 EPA is authorized to revise the list of hazardous substances subject to these criteria as may be appropriate. EPA finalized the initial list of hazardous substances in 1978 and thereafter revised the list in 1979, 1989, and 2011.122 118 EPA, PFAS Strategic Roadmap, p. 15. 119 Ibid. 120 Section 101(14) of CERCLA (42 U.S.C. §9601(14)) generally defines the term hazardous substance to include hazardous substances designated under Section 311(b)(2)(A) of the CWA; toxic pollutants listed under Section 307(a) of the CWA; hazardous waste with characteristics identified or listed under Section 3001 of the Solid Waste Disposal Act (with the exception of wastes excluded from regulation); hazardous air pollutants listed under Section 112 of the Clean Air Act; any imminently hazardous chemical substance or mixture for which EPA has taken action under Section 7 of TSCA; and other elements, compounds, mixtures, solutions, and substances designated pursuant to Section 102 of CERCLA. 121 33 U.S.C. §1321(b)(2)(A). CWA Section 311(b)(3) generally prohibits the discharge of a hazardous substance (or oil) in “harmful” quantities into or upon the navigable waters of the United States, adjoining shorelines, or the waters of the contiguous zone or in connection with activities under the Outer Continental Shelf Lands Act or the Deepwater Port Act of 1974 or that may affect natural resources belonging to, appertaining to, or under the exclusive management authority of the United States. However, Section 311(a)(2) of the CWA (33 U.S.C. §1321(a)(2)) defines the term discharge to exclude discharges in compliance with a permit issued under CWA Section 402, making such compliant discharges not prohibited. 122 The list of hazardous substances designated under CWA Section 311 is codified at 40 C.F.R. §116.4. The original list published by EPA in 1978 included 271 hazardous substances. While 28 substances were added the following year, the list has changed slightly since that time and currently includes 296 substances. Congressional Research Service 17 Contaminants of Emerging Concern Under the Clean Water Act Pursuant to Section 311(b)(4), EPA established “harmful” quantities for these substances that are subject to the reporting of discharges prohibited under Section 311(b)(3).123 Section 311(b)(5) requires a person in charge of a vessel or facility to notify the National Response Center, administered by the U.S. Coast Guard, as soon as that person has knowledge of a discharge.124 Discharges permitted under other provisions of the CWA or otherwise allowable under certain other federal, state, and local regulations are excluded from reporting under CWA Section 311.125 CWA Section 311(c) authorizes federal actions to remove a prohibited discharge of a hazardous substance (or oil).126 CWA Section 311(f) establishes liability for the recovery of removal costs, including restoration of damaged natural resources.127 Section 311(e) authorizes enforcement orders to require a responsible party to abate an imminent and substantial threat to public health or welfare from a prohibited discharge, or threat of a harmful discharge, of a hazardous substance (or oil).128 Implications of CWA Designations on CERCLA If EPA were to designate a CEC, or any contaminant, as a toxic pollutant or hazardous substance under the CWA, that contaminant would, by statutory definition, be defined as a hazardous substance under CERCLA. CERCLA authorizes federal actions to respond to a release, or substantial threat of a release, of a hazardous substance into the environment in coordination with the states. CERCLA similarly authorizes response actions for releases of other pollutants or contaminants that may present an imminent and substantial danger to public health or welfare. CERCLA also establishes liability for response costs and natural resource damages but only for hazardous substances and not for other pollutants or contaminants. CERCLA response authority is available for releases of pollutants or contaminants but without liability to require a potentially responsible party to perform or pay for response actions. Designating a CEC as a toxic pollutant or hazardous substance under the CWA would have the effect of establishing liability for their release as a hazardous substance under CERCLA. However, releases in compliance with a CWA permit would be exempt from liability under CERCLA as a “federally permitted release” based on the premise that the permit requirements would mitigate potential risks.129 CWA Section 311 also establishes liability for releases of hazardous substances, but CERCLA liability and enforcement mechanisms are broader than the CWA. In practice, CERCLA has been the principal federal authority used to respond to discharges of hazardous substances into surface waters and to enforce liability, although the enforcement authorities of CWA Section 311 remain 123 33 U.S.C. §1321(b)(4). 124 33 U.S.C. §1321(b)(5). 125 Quantities of “harmful” discharges of hazardous substances subject to reporting under CWA Section 311 are codified at 40 C.F.R. §117. 126 33 U.S.C. §1321(c). 127 33 U.S.C. §1321(f). 128 33 U.S.C. §1321(e). Such threats may include threats to fish, shellfish, wildlife, public and private property, shorelines, beaches, habitat, and other living and nonliving natural resources under the jurisdiction or control of the United States. 129 Section 107(j) of CERCLA (42 U.S.C. §9607(j)) exempts federally permitted releases from liability under the statute. Section 101(10) of CERCLA (42 U.S.C. §9601(10)) defines the term federally permitted release to include discharges permitted under Sections 402 and 404 of the CWA and releases permitted under various other federal environmental laws. Congressional Research Service 18 link to page 11 Contaminants of Emerging Concern Under the Clean Water Act available to EPA. For a broader discussion of CERCLA, see CRS Report R41039, Comprehensive Environmental Response, Compensation, and Liability Act: A Summary of Superfund Cleanup Authorities and Related Provisions of the Act, by David M. Bearden. Legislation in the 117th Congress Recent congressional interest in CECs has largely focused on addressing one particular group of CECs—PFAS—and addressing them through several statutes, such as the Safe Drinking Water Act.130 In the 117th Congress, some Members have continued to introduce bills that would direct EPA to take regulatory and other actions to address PFAS under several environmental statutes. Some bills introduced in the 117th Congress also propose to address PFAS, microplastics, or other CECs using CWA authorities. In October 2021, the House Transportation and Infrastructure Committee, Water Resources and Environment Subcommittee, held a hearing focused on CECs—with particular attention to PFAS and microplastics—and the CWA’s framework for addressing such contaminants in surface waters.131 In addition, Congress passed the Infrastructure Investment and Jobs Act, enacted on November 15, 2021 (IIJA; P.L. 117-58), which provides $1 billion over five fiscal years for the primary financial assistance program that supports wastewater infrastructure—the Clean Water State Revolving Fund program, authorized by the CWA—for a range of projects to address emerging contaminants. Bills introduced by Members in the 117th Congress to address PFAS, microplastics, or other CECs using CWA authorities include the following:  H.R. 1915, the Water Quality Protection and Job Creation Act of 2021, would amend the CWA to create, reauthorize, and revise several programs. The bill would create a new grant program for owners of publicly owned treatment works to be used for the implementation of a pretreatment standard or effluent limitation developed pursuant to the CWA for any PFAS or pollutants identified by the EPA Administrator as a CEC.  H.R. 2467, the PFAS Action Act of 2021, would require EPA to take a number of actions under several statutes. Among these are CWA-related actions focused on ELGs, water quality criteria, and notification. Some of these actions are similar to those proposed in H.R. 3622, S. 1907, and H.R. 4224 (as discussed below). H.R. 2467 would require EPA to develop ELGs for PFAS for nine specified industrial categories no later than four years after the date of enactment.132 It would also require EPA to publish human health water quality criteria for PFAS not later than three years after the date of enactment. The bill includes an authorization of appropriations for EPA to carry out these requirements. The bill would also require the owner or operator of an industrial source of PFAS to notify the applicable treatment facility of any introduction of PFAS to that treatment works, and provide them with certain information regarding the identity, quantity, susceptibility to treatment, and potential interference of the relevant PFAS. 130 For a discussion of select PFAS legislation in the 116th Congress, see CRS Report R45986, Federal Role in Responding to Potential Risks of Per- and Polyfluoroalkyl Substances (PFAS), coordinated by David M. Bearden. 131 U.S. Congress, House Committee on Transportation and Infrastructure, Subcommittee on Water Resources and Environment, Emerging Contaminants, Forever Chemicals, and More: Challenges to Water Quality, Public Health, and Communities, 117th Cong., 1st sess., October 6, 2021. 132 As discussed in an earlier section (“ELGs”), in October 2021, EPA issued its PFAS Strategic Roadmap, which established timelines for action on certain industrial categories, including the nine industrial categories identified in the proposed “PFAS Action Act of 2021” legislation. Congressional Research Service 19 Contaminants of Emerging Concern Under the Clean Water Act  H.R. 3622 and S. 1907, related bills titled the Clean Water Standards for PFAS Act of 2021, would similarly require EPA to develop ELGs for PFAS for nine specified industrial categories not later than four years after the date of enactment. They would require EPA to publish human health water quality criteria for PFAS not later than two years after the date of enactment. The bills would authorize appropriations of $200 million for each of FY2022 through FY2026 for EPA to carry out these requirements.  H.R. 3701, the Protecting Infrastructure and Promoting the Economy Act (PIPE Act), would direct EPA to establish a wastewater discretionary grant program to provide competitive grants to eligible entities for certain eligible wastewater infrastructure projects. Eligible projects would include measures to reduce the discharge of PFAS into the environment through publicly owned treatment works.  H.R. 4224, the PFAS Transparency Act, would require the owner or operator of an industrial source of PFAS to notify the applicable treatment work of any introduction of PFAS to that treatment works, and provide them with certain information regarding the identity, quantity, susceptibility to treatment, and potential interference of the relevant PFAS.  S. 1507, the Plastic Pellet Free Waters Act, would require EPA to promulgate a rule to prohibit the discharge of plastic or pre-production plastic materials from facilities regulated by ELGs under the Organic Chemicals, Plastics, and Synthetic Fibers133 and Plastics Molding and Forming134 industrial categories. It would also require that the rule prohibit discharges of plastic pellets or other pre-production plastic materials from point sources that make, use, package, or transport such materials, and would require that NPDES permits and standards of performance for vessels reflect these prohibitions.  H.R. 2238 and S. 984, companion bills titled the Break Free from Plastic Pollution Act, would require certain actions to address plastic pollution and microplastics through several statutes. Among other actions, the bills would require EPA, in consultation with other agencies, to establish a grant program to fund microfiber reduction projects that either help reduce the generation of microfiber pollution or improve filtration for the removal of microfiber pollution from washing machines or wastewater treatment plants. They would also require EPA to establish a pilot program to test the efficacy and cost effectiveness of tools, technologies, and techniques to remove microplastics from the environment and prevent release into the environment. The bills would require EPA to promulgate revised ELGs, not later than three years after enactment, for the Organic Chemicals, Plastics, and Synthetic Fibers industrial category and the Petroleum Refining category135 to address specified requirements. They would also incorporate the requirements proposed in S. 1507, the Plastic Pellet Free Waters Act. In addition, they would require that no later than three years after enactment, EPA promulgate a rule to ensure that proposed CWA permits for certain facilities identified in the bill address potential environmental justice impacts. 133 40 C.F.R. §414. 134 40 C.F.R. §463. 135 40 C.F.R. §419. Congressional Research Service 20 Contaminants of Emerging Concern Under the Clean Water Act Conclusion While Congress is currently debating how to best address the concerns related to widespread detections of PFAS, attention to other emerging contaminants (e.g., microplastics and algal toxins) has also increased, together with the availability of new detection methods and increased monitoring. Observers note that in the coming years, other CECs will likely emerge and prompt similar calls for immediate action to protect public health and the environment. Many observers argue that federal actions to address CECs currently tend to be reactive rather than proactive. Many of these observers assert that more focus and attention is needed on assessing the toxicity of chemical substances before they are introduced into commerce. Congress is currently considering legislation to improve federal coordination and responses to CECs. Specific to the CWA, some observers advocate for oversight to identify and address potential gaps or barriers in CWA authorities and processes that make it difficult for EPA and states to quickly respond when CECs are detected. Other observers assert that EPA could better use its existing authorities to address CECs. For example, EPA has not updated its ELGs for certain industrial categories in decades. Accordingly, some observers assert that various ELGs do not reflect advancements in science or technology that could lead to new effluent limitations for CECs. Similarly, some stakeholders assert that EPA could better prioritize which CECs warrant water quality criteria development. EPA’s ability to address these and other recommendations depends on the availability of resources, treatment technologies, and scientific and economic data. Moving forward, Congress may be interested in evaluating EPA appropriations for the CWA programs that support EPA’s efforts to address discharges of CECs. Congress may also be interested in overseeing the Administration’s implementation of these programs. Author Information Laura Gatz Analyst in Environmental Policy Disclaimer This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you wish to copy or otherwise use copyrighted material. Congressional Research Service R45998 · VERSION 3 · UPDATED 21 and incorporate monitoring and other data (e.g., ambient water concentrations).¹⁰¹

Designating CECs as Toxic Pollutants or Hazardous Substances

Toxic Pollutants—CWA Section 307

Hazardous Substances—CWA Section 311

Implications of CWA Designations on CERCLA

Legislation in the 116^th Congress

Conclusion