A 2004 EPA report to Congress estimated that there are 9,348 CSO outflows in the U.S., discharging about of untreated wastewater and storm water to the environment. EPA estimates that between 23,000 and 75,000 sanitary sewer overflows occur each year, resulting in releases of between 3 and of untreated wastewater. The increased frequency and intensity of rainfall as a result of climate change will result in additional water pollution from wastewater treatment, storage, and conveyance systems." For the most part, wastewater treatment plants and CSO control programs have been designed on the basis of the historic hydrologic record, taking no account of prospective changes in flow conditions due to climate change. Drinking water quality In 2015, 9% of 500-person-or-larger community water systems monitored by the EPA, covering approximately 21 million people, violated at least one health standard. Between 1984 and 2018, between 4 and 28% of the American population received contaminated water in any given year. There are several aspects of drinking water quality that are of some concern in the United States, including Cryptosporidium, disinfection by-products, lead, perchlorates, per- and polyfluoroalkyl substances (PFAS) and pharmaceutical substances. While lead in drinking water continues to persist as a public health problem in some communities, the source of the lead is generally from the lead service lines, rather than the water delivered by the utility. EPA's Lead and Copper Rule (LCR) does not set an MCL, but requires a utility to take action when the lead level at a customer location reaches 0.015 mg/L. A typical utility action is to adjust the chemistry of the drinking water with anti-corrosive additives, but replacement of lead service lines (pipes that connect the water main to the home) is also an option. Most communities have avoided lead service line replacement due to the high cost. Congress passed the Reduction of Lead in Drinking Water Act tightening the definition of "lead free" plumbing, in 2011. EPA published a final rule implementing the law on September 1, 2020. In response to the Flint, Michigan water crisis, EPA published a revised LCR on January 15, 2021 addressing testing, pipe replacement and related issues. The rule mandates additional requirements for sampling tap water, corrosion control, public outreach and testing water in schools. The rule continues the requirement for replacement of lead service lines when the "action level" for lead is exceeded, but requires that a utility replace at least