The Lead and Copper Rule (LCR) is a United States federal regulation that limits the concentration of lead and copper allowed in public drinking water at the consumer's tap, as well as limiting the permissible amount of pipe corrosion occurring due to the water itself. The U.S. Environmental Protection Agency (EPA) first issued the rule in 1991 pursuant to the Safe Drinking Water Act (SDWA). The EPA promulgated the regulations following studies that concluded that copper and lead have an adverse effect on individuals. The LCR limits the levels of these metals in water through improving water treatment centers, determining copper and lead levels for customers who use lead plumbing parts, and eliminating the water source as a source of lead and copper. If the lead and copper levels exceed the "action levels", water suppliers are required to educate their consumers on how to reduce exposure to lead. In a 2005 report EPA stated that the LCR requirements had been effective in 96 percent of systems serving at least 3,300 people. The EPA has stated that the LCR has reduced exposure to lead "that can cause damage to brain, red blood cells, and kidneys, especially for young children and pregnant women." It also explained that the rule has reduced copper exposure "that can cause stomach and intestinal distress, liver or kidney damage, and complications of Wilson’s disease in genetically predisposed people." EPA published a revised LCR in 2021. Background Although lead is a known poison, the mechanical and chemical characteristics of the metal continue to keep lead as an important component in many products. In water supply, lead's durability and workability made it preferable for use as water pipes (as compared to, for example, iron pipes). Lead alloys (bronze, brass) are used for plumbing fittings, and lead solders were also preferred. While state and local governments began to prohibit installation of lead pipes early in the twentieth century, lead alloys continued to be used. Alternative pipe materials have been iron, copper, and later plastics. Although new lead pipes weren't installed later in the 20th century, some existing lead pipes remain in service in many cities. The U.S. Public Health Service published a non-enforceable standard for lead in 1925, consisting of a tolerance limit of 0.1 mg/L. Partially because of the continued use of lead pipes, some states regulated the corrosivity of treated water put into the distribution system. Waters which