text: Background Generally, the responsibility for reducing lead in drinking water and ensuring safe drinking water overall is shared by EPA, states, and local water systems. EPA is responsible for, among other things, national implementation of the Lead and Copper Rule, setting standards, overseeing states’ implementation of the rule, and conducting some enforcement activities. However, most states have primary responsibility for enforcing the requirements under SDWA as amended. Water systems are generally subject to requirements under SDWA as amended, such as the Lead and Copper Rule, and are responsible for managing and funding the activities and infrastructure needed to meet those requirements. Such infrastructure includes storage facilities and drinking water mains and may include other pipes such as service lines. There are 1 million miles of drinking water mains in the country, according to a 2017 American Society of Civil Engineers study. As figure 1 illustrates, service lines are the smaller pipes that connect the water mains to homes and buildings. According to EPA guidance, service lines also include any smaller pipes used for connecting a service line to the water mains (e.g., gooseneck pipes which are also known as pigtails). Service lines can generally be made of lead, steel, copper, or plastic. Service lines can be fully owned by the water system (publicly owned) or by the homeowner (privately owned), or ownership can be shared. In most communities, lead service lines are partially owned by the water system and partially owned by the homeowner. With shared ownership, the water system typically owns the service line from the water main to the curb stop, and the homeowner owns the service line from the curb stop into the home. In such cases, each party is responsible for maintaining the part of the service line that it owns. In some circumstances, if lead levels are higher than the Lead and Copper Rule allows and other measures do not alleviate the problem, the Lead and Copper Rule requires water systems to replace lead service lines under the systems’ control. The Lead and Copper Rule does not require homeowners to replace the portion of lead service lines they own, but if they choose to do so they are generally responsible for the associated costs. The Lead and Copper Rule allows for a partial replacement by the water system when an owner of a home or building is unable or unwilling to pay for replacement of the portion of the service line not owned by the water system. The Total Number of Lead Service Lines Is Unknown, and National, State, and Local Estimates Vary The total number of lead service lines is unknown and while national, state, and local estimates exist, approaches used to count lead service lines vary. The total number of lead service lines is unknown because, among other things, the Lead and Copper Rule does not require all water systems to collect such information. National, state, and local estimates exist, but the methods used to arrive at these estimates vary, making it challenging to compare estimates. The Lead and Copper Rule Does Not Generally Require Water Systems to Maintain Complete Information about Lead Service Lines or Report Such Information to EPA The total number of lead service lines is unknown, in part because the Lead and Copper Rule does not require all water systems to develop and maintain a complete inventory of lead service lines, and there are no national repositories of information about lead service lines. According to EPA headquarters officials we interviewed in 2017, the materials inventory required under the Lead and Copper Rule is not intended to be a census of lead service lines (and other lead pipes such as goosenecks/ pigtails). Instead, it is intended to provide sufficient information to develop a plan for periodically obtaining tap samples. For example, according to 2008 EPA guidance to water systems, if a system contains lead service lines, then, if possible, half of the sample sites should include those served by a lead service line. The Lead and Copper Rule requires water systems to conduct complete inventories only if the water system is required to begin replacing lead service lines. In these instances, water systems are required to expand the materials inventory to a complete inventory that identifies the total number of lead service lines for the purpose of tracking replacements over time. As we reported in 2017, based on the available data, the majority of the 68,000 water systems subject to the Lead and Copper Rule at the time of our review had not been required to replace lead service lines and therefore were not required to conduct complete inventories. Moreover, there are no national repositories for information about lead service lines. In September 2017, we recommended that, as a part of revisions to the Lead and Copper Rule, EPA require states to report data on lead pipes (including lead service lines) and incorporate these data in the agency’s Safe Drinking Water Information System. EPA agreed with the recommendation but has not implemented it. In May 2018, EPA noted that it was in the process of reviewing comments received through consultations with state and local officials and tribes. According to EPA officials, final revisions to the Lead and Copper Rule are expected by February 2020. We continue to believe that EPA should collect data about lead pipes (including lead service lines) from states. By doing so, EPA and congressional decision makers would have important information at the national level on what is known about lead infrastructure in the country, thereby facilitating oversight of the Lead and Copper Rule. National, State, and Local Estimates of Lead Service Lines Exist, and Those We Reviewed Had Significant Limitations; but the Methods Used to Arrive at These Estimates Vary The total number of lead service lines is unknown, and while some entities have developed estimates of lead service lines at the national, state, or local water system level, the estimates we reviewed have significant limitations to their reliability. Moreover, the approaches used to arrive at these estimates vary, making it challenging to compare estimates. Nationally, according to EPA’s October 2016 Lead and Copper Rule Revisions White Paper, there are an estimated 6.5 million to 10 million homes served by lead service lines. This range of estimates, based in part on data from a study for the 1991 Lead and Copper Rule, has significant limitations. In appendix I we explain why EPA’s estimate may not accurately reflect the total number of lead service lines, nationwide. An April 2016 American Water Works Association study estimated 6.1 million lead service lines nationwide. The authors of this study extrapolated the number based on survey responses from 978 water systems in 2011 and 2013. While this study is the most recent attempt to provide a national estimate, it has significant limitations. First, the sample was not statistically representative of all 68,000 water systems subject to the Lead and Copper Rule. Rather, the water systems that responded to the American Water Works Association’s survey are not a statistical sample. Second, according to the study’s authors, survey responses were based on water systems’ best guesses of the number of lead service lines in their systems. However, since water systems have not been required to maintain inventories of lead service lines, many of them do not know the exact number. For these reasons, we are not confident that the number accurately reflects the total number of lead service lines nationwide. An American Water Works Association official told us that the organization is not planning to update the study. EPA officials told us that they were not aware of a more recent study than the association’s 2016 study. In addition, EPA officials said in May 2018 that the results in the American Water Works Association study likely represent a lower-bound estimate for the number of lead service lines in the country because the sample was not generalizable, and had other data quality issues. EPA officials in one region we interviewed said that estimates of lead service lines can decrease or increase as a water system replaces lead service lines and as a water system does or does not count lead service lines on private property. The Lead and Copper Rule does not require states to collect statewide information about lead service lines, but at least two states collected data from water systems in their states and published reports with these data: A 2016 report by the Massachusetts Department of Environmental Protection’s Drinking Water Program reported 22,023 lead service lines and 15,809 lead goosenecks and pigtails statewide. The report counted goosenecks and pigtails separately from lead service lines. Officials from the Massachusetts Department of Environmental Protection told us that the state has about 2 million service lines total; therefore, about 1 percent of the total service lines are lead. A 2017 report by the Washington State Department of Health estimated 1,000-2,000 lead service lines statewide and 8,000 goosenecks statewide. According to Washington State officials, they continued to update their estimates in early 2018 with selected water utilities. Generally, the purpose of both studies, as stated in each report, was to identify areas in which water systems would need technical assistance in complying with the Lead and Copper Rule or state requirements. However, for the purposes of estimating the number of lead service lines, complete details were not available about the methodologies and some systems that did respond were only able to provide rough guesses rather than precise counts of lead service lines. EPA headquarters officials told us that Massachusetts and Washington were at the forefront of states’ efforts to gather information about lead service lines. EPA officials also told us that they were not aware of any other states with published reports estimating the number of lead service lines. However, at least two states have also collected information about lead service lines but have not published the information in official reports, at the time of our review. For example, in 2016, officials in Indiana and Maryland sent questionnaires to water systems in their states asking for information about the number of lead service lines. A representative of a water association told us that, generally, water systems were in the beginning stages of conducting complete inventories of lead service lines. However, some local water systems also have estimates. For example, EPA officials told us that water systems in the states of Ohio, Michigan, and Washington had estimates of lead service lines. In May 2018, a representative of the Greater Cincinnati Water Works water system estimated there were approximately 7 percent of publicly owned and approximately 18 percent privately owned lead service lines out of a total of 240,000 service lines in the area served by that water system. In March 2018, representatives of the Greater Cincinnati Water Works water system said that their estimates of lead service lines are best characterized as what is known at any given point in time. These representatives also told us that they collect this information on a continual basis from historical and on-going maintenance records, reports of lead service lines by customers, and the water system’s lead service line replacement program, among other sources. To conduct complete inventories and develop estimates, water systems have used varying approaches, which can hinder comparisons among states and water systems. The publicly available reports that existed as of May 2018 provide some insight into the various approaches water systems have used. For example, to identify lead service lines, water systems have used visual inspection or a combination of visual inspections, existing water system records, and discussions with homeowners. In addition, water systems have used various definitions of lead service lines. For example, water systems have counted: only active service lines delivering water to customers, or both active and inactive (no longer delivering water to customers) service lines; or only the publicly owned lead service lines, or both the publicly and privately owned portions of the lead service lines; or only lead service lines or the lead service lines and goosenecks/pigtails separately. Most States Reported Fulfilling EPA’s Request, but Potential Challenges Remain that EPA Information Sharing Could Help to Address While most states informed EPA that they intend to fulfill the agency’s request to work with water systems to publicize inventories of lead service lines, EPA has identified potential challenges to these efforts. Nonetheless, the agency has not followed up with all states since 2016 to share information about how to address these challenges. Most states that said they intended to fulfill EPA’s request to encourage water systems to publicize materials inventories reported in subsequent letters to or meetings with EPA that they did so; however, as of May 2018, most large waters systems had not made such information public. Most States Reported Fulfilling EPA’s Request to Encourage Water Systems to Publicize Materials Inventories, but Most Large Water Systems GAO Reviewed Did Not Do So Our analysis of states’ written responses to EPA’s 2016 request, and information obtained through interviews with EPA officials as of February 2018, found that most (43) of the 50 states indicated an intent to fulfill EPA’s request, 3 states said that they may consider it, and 4 states did not intend to fulfill EPA’s request. Of the approximately 43 states that responded that they would fulfill EPA’s request, almost all (39) reported in subsequent letters to or meetings with EPA that they had encouraged water systems to publicize their materials inventories or other information about lead service lines. In these letters and meetings, states also reported taking other actions to increase their knowledge about lead service lines such as requesting that water systems update the materials inventory required by the Lead and Copper Rule, creating online repositories of maps of lead service lines, posting reports on lead service lines, and issuing requirements for water systems to collect information on lead service lines. For example, in May 2016, the governor of Washington issued a directive requiring the state’s Department of Health to work with certain water systems to identify all lead service lines and lead components within 2 years. Figure 2 shows the number of states that reported fulfilling EPA’s request or taking other related actions. Because EPA asked states to prioritize large water systems (those servicing populations greater than 50,000), we reviewed the websites for the 100 largest water systems. As of January 2018, we found 12 of these water systems had publicized information on the inventory of lead service lines; the rest had not. The information on the websites for the 12 water systems varied. For example, the water system for Tulsa, Oklahoma posted a map that highlighted where lead service lines may be present. Water systems such as Cincinnati, Ohio, Boston, Massachusetts, and Washington, D.C., provided interactive maps that showed locations identified as having lead service lines. See figure 3 for examples of the interactive maps of lead service lines that some selected large water systems have provided to the public. Water systems that serve populations greater than 50,000 but were not among the 100 largest water systems at the time of our review may have also publicized information on the inventory of lead service lines. For example, the water systems for Akron, Ohio, Flint, Michigan, and Providence, Rhode Island each publicized an interactive or other type of map of lead service lines. EPA Identified Potential Challenges to Publicizing Materials Inventories but Has Not Followed Up with All States about How to Address Such Challenges Since 2016 EPA officials in the regional offices provided a range of reasons why water systems may be challenged in conducting inventories of lead service lines and making any information about lead service lines public, however, it has not followed up with all states about how to address such challenges since 2016. In September 2017, we reported that the six states that would not fulfill EPA’s 2016 request had highlighted challenges in finding historical documentation about lead pipes to create plans for collecting tap water samples or in dedicating staff resources to do so. In January and February 2018, some officials whom we interviewed in EPA’s 10 regional offices agreed that these would be challenges for states and water systems. The officials also mentioned additional potential challenges in conducting complete inventories of lead service lines or publicizing information about lead service lines. Table 1 describes the challenges mentioned by EPA officials in the 10 regional offices. Since the February 2016 letter, EPA followed up in July 2016 with a letter to the Association of State and Territorial Health Officials and Environmental Council of States, which represents all states. In that letter, EPA provided two examples of state practices that increase public transparency: some drinking water systems are providing online searchable databases that provide information on known locations of lead service lines, or are providing videos that show homeowners how to determine whether their home is served by a lead service line. The letter also said that EPA would continue to work with states to ensure that the identification of the locations of lead service lines remains a priority for drinking water systems. However, EPA has conducted limited follow-up since then, mainly, EPA headquarters and regional officials said, because they have focused their efforts on ensuring states appropriately comply with the Lead and Copper Rule. As previously noted in this report, posting materials inventories or other information about the location of lead service lines is not a requirement of the Lead and Copper Rule. In May 2018, EPA headquarters officials we interviewed said that they learned of some states’ and water systems’ efforts toward making information about lead service lines available to the public since 2016, through conferences and discussions with states. These headquarters officials told us that they have shared such efforts with those states who, in 2016, said they did not intend to fulfill EPA’s 2016 request. For example, EPA shared how states that were publicizing information about lead service lines were addressing privacy concerns with states that originally said they would not fulfill EPA’s request. However, as of January 2018, most of the 100 largest water systems had not made their materials inventories or additional maps or updated inventories public. According to EPA’s February 2016 letter, the agency’s objective in encouraging states to work with water systems to post, on a public website, the water system’s original materials inventory along with any additional updated map or inventories of lead service lines was to assure the public that lead risks were being addressed. Under federal standards for internal control, management should externally communicate the necessary quality information, so that external parties can help to achieve the entity’s objectives. By sharing information with all states about the approaches that some states and water systems are using to successfully identify and publicize information about lead service lines, including responses to potential challenges, EPA could encourage states to be more transparent to the public and support the agency’s objectives for safe drinking water. Conclusions Lead service lines present a significant risk of lead contamination in drinking water. Publicizing drinking water systems’ knowledge about lead service lines, and other lead infrastructure, would facilitate oversight of the Lead and Copper Rule. In September 2017, we recommended that, as a part of revisions to the Lead and Copper Rule expected by February 2020, EPA require states to report data on lead pipes (including lead service lines) and incorporate these data in the agency’s Safe Drinking Water Information System. EPA agreed with the recommendation, and we continue to believe that EPA should require data about lead pipes (including lead service lines) from states. Most states reported that they had encouraged their water systems to publicize information about lead service lines in response to EPA’s February 2016 requests. EPA headquarters officials told us that they had learned of some states’ and water systems’ efforts since 2016 and shared this information with the few states that said that they would not take action in response to EPA’s letter. This information did in fact help at least one state take action, according to information we received from EPA and the state. By sharing information with all states about the approaches that some states and water systems are using to successfully identify and publicize information about lead service lines, including responses to potential challenges, EPA could encourage states to be more transparent to the public and support the agency’s objectives for safe drinking water. Recommendation for Executive Action The Assistant Administrator for Water of EPA’s Office of Water should share information with all states about the approaches that some states and water systems are using to successfully identify and publicize information on lead service lines, including responses to potential challenges. (Recommendation 1) Agency Comments We provided a draft of this report to EPA for review and comment. In its comments, reproduced in appendix II, EPA agreed with our recommendation. The agency also highlighted a recently developed website that showcases efforts to identify and replace lead service lines and said that it will continue to ensure states and water systems are aware of this resource. We are sending copies of this report to the appropriate congressional committees, the Administrator of EPA, and other interested parties. In addition, the report is available at no charge on the GAO website at http://www.gao.gov. If you or your staff members have any questions about this report, please contact me at (202) 512-3841 or gomezj@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. Key contributors to this report are listed in appendix III. Appendix I: Objectives Scope and Methodology Our objectives were to examine (1) what is known about the number of existing lead service lines nationally, and among states and water systems; and (2) state responses to EPA’s February 2016 request to work with water systems to publicize inventories of lead service lines and any steps EPA has taken to follow up on these responses. To examine what is known about the number of existing lead service lines nationally, and among states and water systems, we relied on interviews and publicly available reports for which we could assess the reliability of the data. We reviewed the requirements under the Lead and Copper Rule for assessing the number of lead service lines. We interviewed officials from EPA’s Office of Water and the following water organizations concerning what these officials knew about the number of lead service lines nationally and among states and water systems: the American Water Works Association, Association of State Drinking Water Administrators, and Regional Community Assistance Partnership. We also interviewed an official with the Environmental Defense Fund regarding the available information about the number of lead service lines nationally and among states and water systems. We selected these organizations because they are all members of the Lead Service Line Replacement Collaborative, a consortium that provides information about voluntary lead service line replacement for states and water systems. On behalf of the Lead Service Line Replacement Collaborative, the organizations we spoke with are collecting examples of states’ and water systems’ experiences in conducting inventories of lead service lines, as the first step in replacing lead service lines. Using information from these interviews, we identified three published studies from the American Water Works Association, the state of Massachusetts, and the state of Washington. We interviewed the authors of the studies to determine the reliability, completeness, and accuracy of the data presented in the studies. For the 2016 American Water Works Association study, we determined that the data were of undetermined reliability because the responses of the water systems surveyed were not generalizable to all water systems and the study authors could not verify the accuracy of the information. Specifically, the sample in the 2016 American Water Works Association study was not based on a statistical sample, and therefore the sampling error was not calculated and information was not available to determine whether responding water systems were similar to nonresponding water systems. For example, the estimate is based on survey responses from 978 of the approximately 23,000 water systems that existed around the time of the surveys, and therefore may not represent all water systems nationwide. In addition, since many water systems do not have complete inventories of their lead service lines, the accuracy of data that water systems submitted in response to the survey is difficult to verify. For example, our interview with the study authors indicates that the information provided by water systems varied in quality, with some systems basing their responses on rough estimates. We based our determination about the data using the criteria of Total Survey Error, which is a framework for assessing the validity and reliability of survey estimates. It includes sampling error (the difference between the population and the sample), nonresponse error, measurement error (the difference between the true response and the response provided by the respondent) and coverage error (the discrepancy between the list of individuals that is used to select a sample and the target population). EPA’s 2016 Lead and Copper Rule Revisions White Paper also identified an estimate of lead service lines. According to EPA officials, this estimate used data from the 2016 American Water Works Association study and a 1988 American Water Works Association study cited in the regulatory impact analysis for the 1991 Lead and Copper Rule. The 1991 estimate also had significant limitations in measurement error and representation error as well as a lack of documentation about key aspects of the methodology. As such, we determined the estimate was not reliable for the purposes of establishing the total number of lead service lines in existence as of 1991. The two state-specific studies represent reasonable efforts to estimate the number of lead service lines in these states. However, they generally could not verify the accuracy of the information provided by these systems because, as we note elsewhere in this report, water systems may not know the number of lead service lines they have. Therefore, for the state-specific studies, we also determined that the data were also of undetermined reliability. Finally, while the Greater Cincinnati Water Works water system did not publish a report about lead service lines, we collected the information through an in-person interview and corroborated the information through a review of the water system’s geographic information system database. The Greater Cincinnati Water Works’ GIS database includes the location and material information for all of the water system’s distribution system. According to the Greater Cincinnati Water Works website, the water system continues to update its map as it obtains more information from its customers. Based on these steps we deemed the data provided by the water system to be sufficiently reliable for the purposes of describing the estimate reported by representatives of the Greater Cincinnati Water Works system. To examine states’ responses to EPA’s February 2016 request to work with water systems to publicize inventories of lead service lines and any steps EPA has taken to follow up on these responses, we relied both on the publicly available letters from each state to EPA and on interviews with EPA regional and headquarters officials. We did not interview state officials in all 50 states, but reviewed some state documents, where available. We used a standard set of open-ended questions to interview officials in EPA’s headquarters and in each of the 10 regional offices. To analyze states’ and EPA officials’ responses, we conducted two analyses. Specifically, we conducted two analyses to summarize updates in state responses to EPA’s February 2016 letter and EPA’s responses to challenges states and water systems may face in conducting and publicizing materials inventories. To confirm each analysis, one analyst independently summarized the information and another analyst verified the accuracy of the information. All initial disagreements were discussed and reconciled. All numbers in our analysis are considered approximate because interpretations of the states’ responses to EPA’s 2016 letter can differ, and states may have taken actions after our interviews with EPA regional officials, or may have taken actions that they did not report to EPA. Figure 4 shows the EPA regions and the states within those regions. We also reviewed EPA documents related to EPA’s request that states take certain actions following the events in Flint, Michigan. In addition, we reviewed federal regulations; EPA guidance to water systems on how to implement the Lead and Copper Rule; and other relevant documents such as an EPA white paper. Because EPA asked states to place an emphasis on working with large water systems to publicize their materials inventories or updated inventories or maps of lead service lines, we reviewed the websites of the 100 largest water systems by population. Our review was conducted in January to February 2018; and since then, additional water systems may have provided information to the public on lead service lines. We identified the largest water systems, based on population served, from data in EPA’s Safe Drinking Water Information System/Fed. EPA has stated on its website that the agency acknowledges challenges related to the data in the Safe Drinking Water Information System/Fed, specifically underreporting of some data by states. GAO has also reported on EPA’s challenges with the Safe Drinking Water Information System/Fed. Even with these challenges, the information on the populations served by water systems in the Safe Drinking Water Information System/Fed is generally reliable. We used a standard set of search terms on each website to ensure the consistency of our searches, as well as information from water organizations and EPA officials, where applicable. We counted a water system as having an inventory if the water system provided a map, interactive map, list of pipes or service lines, or numerical count of lead service lines available to the public. To ensure the completeness of this analysis, one analyst independently conducted the search of websites and another analyst verified the search. All initial disagreements were discussed and reconciled. We compared EPA’s actions to follow up on state responses with federal standards for internal control for information and communication. We conducted this performance audit from October 2017 to September 2018 in accordance with generally accepted government auditing standards. Those standards require that we plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe that the evidence obtained provides a reasonable basis for our findings and conclusions based on our audit objectives. Appendix II: Comments from the U.S. Environmental Protection Agency Appendix III: GAO Contact and Staff Acknowledgments GAO Contact Staff Acknowledgments In addition to the contact named above, Diane Raynes (Assistant Director); Tahra Nichols (Analyst in Charge); David Blanding, Jr.; Mark Braza; Lawrence Crockett, Jr.; Justin Fisher; Richard P. Johnson, and Jeanette Soares made key contributions to this report. In addition, Cynthia Norris and Dan Royer made important contributions. Related GAO Products Drinking Water: Additional Data and Statistical Analysis May Enhance EPA’s Oversight of the Lead and Copper Rule. GAO-17-424. Washington, D.C.: September 1, 2017. Water Infrastructure: Information on Selected Midsize and Large Cities with Declining Populations. GAO-16-785. Washington, D.C.: September 15, 2016. Water Infrastructure: EPA and USDA Are Helping Small Water Utilities with Asset Management; Opportunities Exist to Better Track Results. GAO-16-237. Washington, D.C.: January, 27, 2016. Drinking Water: Unreliable State Data Limit EPA’s Ability to Target Enforcement Priorities and Communicate Water Systems’ Performance. GAO-11-381. Washington, D.C.: June 17, 2011. Drinking Water: The District of Columbia and Communities Nationwide Face Serious Challenges in Their Efforts to Safeguard Water Supplies. GAO-08-687T. Washington, D.C.: April 15, 2008. Drinking Water: EPA Should Strengthen Ongoing Efforts to Ensure That Consumers Are Protected from Lead Contamination. GAO-06-148. Washington, D.C.: January 4, 2006. District of Columbia’s Drinking Water: Agencies Have Improved Coordination, but Key Challenges Remain in Protecting the Public from Elevated Lead Levels. GAO-05-344. Washington, D.C.: March 31, 2005. Drinking Water: Safeguarding the District of Columbia’s Supplies and Applying Lessons Learned to Other Systems. GAO-04-974T. Washington, D.C.: July 22, 2004.
target: The crisis in Flint, Michigan, brought increased attention to lead in drinking water infrastructure. Lead in drinking water primarily comes from corrosion of service lines connecting the water main to a house or building. In 1991, EPA issued the Lead and Copper Rule that required water systems to conduct a “materials inventory” of lead service lines. In light of the events in Flint, EPA sent a letter to all states in February 2016 encouraging them to work with water systems to publicly post the materials inventory, along with any additional updated maps or inventories of lead service linesactions the rule does not require. A House Committee report accompanying a bill for the Department of the Interior, Environment and Related Agencies Appropriations Act, 2017, includes a provision for GAO to review lead service lines. This report examines (1) what is known about the number of existing lead service lines among states and water systems and (2) states' responses to EPA's February 2016 request to work with water systems to publicize inventories of lead service lines and any steps EPA has taken to follow up on these responses. GAO reviewed existing studies of lead service lines, reviewed the websites of the 100 largest water systems, and interviewed EPA officials in headquarters and its 10 regional offices. The total number of lead service lines is unknown and while national, state, and local estimates exist, approaches used to count lead service lines vary. A 2016 American Water Works Association study estimated that nationally there were 6.1 million lead service lines, but the study has significant sampling limitations and, as a result, likely does not accurately reflect the total number of lead service lines nationwide. In addition, at least two statesMassachusetts and Washingtonpublished reports with estimates of lead service lines and reported 22,023 and 1,000-2,000 lead service lines as of 2016 and 2017, respectively. Certain water systems also have estimates, such as the approximately 7 percent of publicly owned lead service lines out of the area's total number of service lines cited by a representative for the system serving Cincinnati, Ohio and surrounding areas, as of May 2018. While most states informed the Environmental Protection Agency (EPA) that they intend to fulfill the agency's request to publicize inventories of lead service lines, EPA has identified potential challenges to these efforts. Of the approximately 43 states that responded that they would fulfill EPA's request, almost all (39) reported to EPA that, although they had encouraged water systems to publicize inventories, few systems had completed these actions. GAO found in January 2018 that, of the 100 largest water systems, 12 had publicized information on the inventory of lead service lines. According to EPA, among challenges in conducting inventories of lead service lines and publicizing information about lead service lines were concerns about posting on public websites information about lead service lines on private property; and a lack of records about the locations of lead service lines. EPA told GAO the agency was focused on state compliance with drinking water rules, and not following up with information on how states could address the challenges cited. By sharing information with all states about the approaches that some states and water systems are using to successfully identify and publicize information about lead service lines, including responses to potential challenges, EPA could encourage states to be more transparent to the public and support the agency's objectives for safe drinking water.