This section provides information on (1) the known health effects of lead in drinking water; (2) how water systems deliver drinking water to the public and where lead may be present; (3) the requirements of the LCR; (4) LCR data that states report to EPA; and (5) the roles of federal, state, and local entities in implementing the LCR. EPA, the Centers for Disease Control and Prevention (CDC), and others have indicated that the rates of lead contamination in the U.S. population have decreased over the years. However, lead remains a significant concern to public health because lead is persistent and can accumulate in the body over time with long-lasting effects, particularly for children and pregnant women. According to EPA documents, low levels of lead exposure in children are linked to hyperactivity, anemia, lower intelligence quotient (IQ), physical and learning disabilities, and slowed growth. In pregnant women, lead can store in bones and be released as maternal calcium used to form the bones of the fetus, reduce fetal growth, and increase risk of miscarriage and stillbirth. For adults, lead can have detrimental effects on cardiovascular, renal, and reproductive systems; and, it can prompt memory loss. The presence of lead in the bloodstream can disappear relatively quickly, but bones can retain the toxin for decades. According to the National Institutes of Health and CDC documents, medications can remove some lead from the body but cannot undo the damage lead causes, although additional services may mitigate some of the damage. Recognizing that vigilance and collaboration are necessary to ensure that children negatively affected by lead exposure receive services designed to compensate for lead’s effect on the brain, and behavior of children, some medical experts promote early-childhood intervention, education, and other programs. According to CDC documents, early intervention for children can help improve IQ scores, academic readiness, and language development as well as decrease placement in special education classes. For these reasons, EPA and others recommend the prevention of lead exposure before it occurs. Water systems depend on distribution systems, both simple and complex, composed of interconnected components to deliver drinking water from a source to their customers. Source water can be either surface (streams, rivers, and lakes) or ground (aquifers). As figure 1 illustrates, the distribution system used to deliver water from the source can include a network of pipes and other components. A distribution system comprises water towers, pipes, pumps, and other components to deliver treated water from treatment systems to consumers. Particularly among larger water systems, distribution systems may contain thousands of miles of pipes, including water mains. There are 1 million miles of drinking water mains in the country, according to a 2017 American Society of Civil Engineers study. Service lines are the smaller pipes that connect the water mains to homes and buildings and can also include smaller pipes used for connecting a service line to the water mains (e.g., called pigtail and gooseneck pipes). In contrast to most other drinking water contaminants, lead is rarely found in the source water. More commonly, lead enters drinking water after the water comes into contact with water mains; service lines; smaller pipes that connect the two; and other plumbing materials that contain lead, such as faucets and water coolers. Schools and day care centers with their own water supplies generally rely on well-water systems using groundwater to deliver drinking water. According to the 2017 American Society of Civil Engineers study and EPA documents, communities, both urban and rural, have aging and deteriorating drinking water infrastructure, which, according to EPA documents, can contribute to lead hazards in drinking water. Since the early 1970s, when several medical studies confirmed that lead exposure negatively impacts health, measures have been taken to reduce the public’s exposure to lead in drinking water, including the enactment of amendments to the SDWA in 1986 and 1996, the enactment of the Lead Contamination Control Act in 1988, the issuance of the LCR in 1991, and amendments to state building codes prohibiting the use of lead pipes. The LCR generally requires water systems to minimize lead in drinking water by controlling the corrosion of metals in the infrastructure they use to deliver water and in household plumbing. EPA has stated that the LCR is one of the most complicated drinking water regulations for states to implement because of the need to control the corrosion of pipes and plumbing fixtures as water is delivered to consumers. The corrosion of pipes results from a chemical interaction between water and pipes that wears the metal away and allows particles of metal to flake away over time. All large water systems (serving populations larger than 50,000) are generally required to install corrosion control treatment. While the majority of the U.S. population receives its drinking water from medium and large water systems, most water systems are small. Characteristics of water can affect the occurrence and rate of corrosion. For example, corrosion occurs more frequently in soft water—water with low concentrations of calcium and magnesium—and also in acidic water, or water with low pH. Water systems control corrosion by adjusting the pH and alkalinity of water or by adding corrosion inhibitors. The LCR establishes corrosion control as the required treatment technique for large water systems and, for medium and small systems, the required treatment technique when the federal lead action level is exceeded (also known as an action level exceedance). Lead concentrations exceeding an action level of 15 parts per billion, or 0.015 milligrams per liter (mg/L), in over 10 percent of tap water samples (i.e., the 90th percentile level) are an indicator that corrosion control is needed or is not working correctly. A water system’s 90th percentile sample result does not exceed the lead action level if it is equal to or less than 15 parts per billion. As figure 2 illustrates, the LCR also requires water systems to identify locations where lead may be present and periodically obtain tap water samples from those locations (of which single-family homes are the highest priority). Under the LCR, an action level exceedance requires the water system and state to take a number of additional steps. Those additional steps require that small and medium water systems install or modify corrosion control treatment, and water systems of all sizes provide information (known as public education) about the harmful effects of lead to consumers and vulnerable populations (e.g., schools, if the water system serves a school, and public health departments). Water systems are also required to test and, if necessary, treat the source water. If, after installing corrosion control and treating source water, a system continues to have 90th percentile sample results that exceed the lead action level, the LCR requires the water system to begin replacing lead service lines, if they exist. In most communities, lead service lines are partially owned by the water system and partially owned by the homeowner. The LCR allows for a partial replacement 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. In an October 2016 study, EPA noted that sample requirements under the LCR are complex for many reasons, one reason being that it is the only drinking water regulation in which homeowners or consumers collect the drinking water samples. Water systems are in compliance with the LCR when they follow the various federal requirements for collecting samples, reporting, installing treatments, providing public education, and replacing lead service lines; as well as when they follow any state requirements that are more stringent than the federal requirements. States and EPA can take several different types of enforcement actions when water systems fail to complete requirements in these areas. Sample results that exceed the lead action level do not by themselves constitute violations of the LCR. The SDWA, as amended in 1996, requires EPA to review and revise, as appropriate, each national primary drinking water regulation, including the LCR, at least once every 6 years. The 1991 LCR was revised in 2000 and 2007. EPA initiated an extensive review of the LCR in 2004 after widespread increases in lead levels were detected in the District of Columbia’s water following a water treatment change. EPA promulgated short-term revisions and clarifications in 2007 and has continued working on comprehensive revisions. In 2016, the agency announced that it would revise the LCR and issue proposed revisions in 2017 and a final revised rule in 2019. EPA also released a Lead and Copper Rule Revisions White Paper in 2016 that outlined potential elements of the rule under consideration for revision such as use of corrosion control practices, requirements for collecting samples, and lead service line replacement. The LCR generally requires that water systems submit data to states to demonstrate their compliance with the treatment technique required by the rule. The LCR also requires states to submit some of these data to EPA’s SDWIS/Fed database on a quarterly basis. Specifically, states are required to submit the following data to EPA: for large and medium water systems, all 90th percentile sample results (i.e., sample results that meet, fall below, and exceed the lead action level); for small water systems, 90th percentile sample results that exceed the lead action level; on water systems that have been designated as having achieved corrosion control because the state has determined that the source water is minimally corrosive; on water systems that were required to install corrosion control treatment, source water treatment, and lead service line replacement and have completed the applicable requirements as a result of having sample results exceed the lead action level; on water systems that have begun the process of replacing lead on water systems that have new violations of the LCR; and on enforcement actions taken in response to violations of the LCR. For corrosion control, the LCR requires the states to report what EPA refers to as “milestone” data to the SDWIS/Fed database: data on the status of required actions, such as installing corrosion control treatment, as required, after reporting sample results that exceed the lead action level; and data on those water systems deemed to have corrosion already under control, such as when the water is minimally corrosive.