Drinking water quality in the United States
Drinking water quality in the United States is generally good. In 2016, over 90 percent of the nation's community water systems were in compliance with all more-than-90 U.S. Environmental Protection Agency (EPA) standards. Most of the systems that are out of compliance are small systems in rural areas and small towns, partly because most public water systems are small ones. Drinking water quality in the U.S. is regulated by state and federal laws and codes, which set Maximum Contaminant Levels (MCLs) for some pollutants and naturally occurring constituents, determine various operational requirements, require public notification for violation of standards, provide guidance to state primacy agencies, and require utilities to publish consumer confidence reports.
Historically, up through 1914, drinking water quality in the country was managed at the state and local level. After that, interstate waters were protected using United States Public Health Service (USPHS) standards. Ultimately the USPHS standards were adopted and expanded as national drinking water standards after passage of the 1974 Safe Drinking Water Act, and U.S. water quality became subject to a whole new generation of federal standards.
Enforcement of standardsEdit
The Safe Drinking Water Act (SDWA) requires EPA to issue federal regulations for public water systems. There are no federal regulations covering private drinking water wells, although some state and local governments have issued rules for these wells. The EPA enters into primary enforcement authority (primacy) agreements with state governments, so in most states the EPA does not directly enforce the SDWA. State rules can be different from the EPA's, but they must be at least as stringent.
The EPA defines a public water system (PWS) as an entity that provides water for human consumption to at least 25 people (or at least 15 connections) for at least 60 days a year. There are three types of public water system: community systems (like cities or trailer parks); non-transient, non-community systems (like factories or schools with their own water source); and transient non-community systems (like rural restaurants or camps).
Enforcement of drinking water standards in small water systems is less consistent than enforcement in large systems. According to a USA Today article published in March 2016, more than 3/4ths of small community water systems classified as having serious health violations by the EPA still have the same violations three years later. Some violations included an overabundance of lead, exceeding allowed rates for nitrate and fecal coliform. Around half of the most contaminated water systems were located in Kansas, Texas and Puerto Rico. In a letter, the EPA’s Office of Enforcement and Compliance Assurance noted that the EPA faced “a daunting list of challenges” in its continuing efforts, particularly with small systems that “lack the basic infrastructure, resources and capacity to provide clean drinking water.” 
Consumer Confidence ReportsEdit
EPA's Consumer Confidence Rule of 1998 requires community public water suppliers to provide customers with annual reports of drinking water quality, called Consumer Confidence Reports (CCR). Each year by July 1 anyone connected to a public water system should receive in the mail an annual water quality report that tells where your water comes from and what's in it. Consumers can find out about these local reports on a map provided by EPA.
The regulation requires water suppliers to list the water sources, report detected contaminants and the system's compliance with National Primary Drinking Water Regulations in the annual reports. Suppliers may also provide additional information such as explanation of the system's treatment processes, advice on water conservation and information about protecting the community's water sources. Elizabeth Royte wrote in 2008 that the reported contaminant numbers are annual averages and that utilities may not provide data on unregulated contaminants.:223 During 2011-2012 EPA conducted a review of the CCR process which including public hearings. EPA agreed with recommendations from commenters that water utilities and regulatory agencies should make improvements to the reports in order to make them more understandable to the public. The Agency planned to accomplish this by providing additional guidance and training to the utilities, and stated that no revisions to the CCR regulation were needed.
Substances for which there are federal standardsEdit
Federal drinking water standards are organized into six groups:
- Disinfection byproducts
- Inorganic chemicals
- Organic chemicals
EPA has issued standards for Cryptosporidium, Giardia lamblia, Legionella, coliform bacteria and enteric viruses. EPA also requires two microorganism-related tests to indicate water quality: plate count and turbidity.
Cryptosporidium is a parasite that has a thick outer shell and thus is highly resistant to disinfection with chlorine. It gets into rivers and lakes from the stools of infected animals. Municipal water treatment plants usually remove Cryptosporidium oocysts through filtration. Nevertheless, at least five outbreaks of cryptosporidiosis in the U.S. have been associated with contaminated drinking water, including a well-publicized one in Milwaukee, Wisconsin in 1993.
The Long Term 2 Enhanced Surface Water Treatment Rule ("LT2 rule") of 2006 requires evaluation of surface water treatment plants and specific treatments be provided in order to minimize the potential for Cryptosporidium infections from public water at supplies using surface water.
Disinfectants such as chlorine can react with natural material in the water to form disinfection byproducts such as trihalomethanes. Animal studies indicate that none of the chlorination byproducts studied to date is a potent carcinogen at concentrations normally found in drinking water. According to the "GreenFacts" website, there is insufficient epidemiological evidence to conclude that drinking chlorinated water causes cancers. The results of currently published studies do not provide convincing evidence that chlorinated water causes adverse pregnancy outcomes.
Arsenic occurs naturally in water or enters it through pollution. If a person drinks two liters (more than half a gallon) of tap water that exceeds the former Maximum Contaminant Level of 50 parts per billion (ppb) every day over a lifetime, there is a risk of cancer. EPA reduced this level to 10 parts per billion (ppb) in 2001 and drinking water systems had to comply with the new regulation starting in 2006. A 2017 Lancet Public Health study found that this rule change led to fewer cancer deaths.
The National Research Council estimates that men and women who daily consume water containing 20 ppb of arsenic have about a 0.7% increased risk of developing bladder or lung cancer during their lifetime. According to a 2009 film, millions of private wells have unknown arsenic levels, and in some areas of the US, over 20 percent of wells may contain levels that are not safe.
Most people associate fluoride with the practice of intentionally adding fluoride to public drinking-water supplies for the prevention of tooth decay. However, fluoride can also enter public water systems from natural sources, including runoff from weathering of fluoride-containing rocks and soils and leaching from soil into groundwater. Fluoride pollution from various industrial emissions can also contaminate water supplies. In a few areas of the United States, fluoride concentrations in water are much higher than normal, mostly from natural sources. In 1986, EPA established a maximum allowable concentration for fluoride in drinking water of 4 milligrams per liter (mg/L). After reviewing research on various health effects from exposure to fluoride, the Committee on Fluoride in Drinking Water of the National Research Council concluded in 2006 that EPA's drinking water standard for fluoride does not protect against adverse health effects. Just over 200,000 Americans live in communities where fluoride levels in drinking water are 4 mg/L or higher. Children in those communities are at risk of developing severe tooth enamel fluorosis, a condition that can cause tooth enamel loss and pitting. It can also increase the risk of bone fractures. The report concluded unanimously that the present maximum contaminant level goal of 4 mg/L for fluoride should be lowered.
Several states have more stringent regulations.
Lead typically gets into drinking water after the water leaves the treatment plant. The source of lead is most likely pipe or solder in older service connections or older plumbing inside homes, from which lead "leaks" into the water through corrosion. EPA's lead and copper rule, last revised in 2007, defines an "action level" of 15 parts per billion (ppb) for lead, which is different from a Maximum Contaminant Level.
If tests show that the level of lead in drinking water is in the area of 15 ppb or higher, it is advisable – especially if there are young children in the home – to replace old pipes, to filter water, or to use bottled water. EPA estimates that more than 40 million U.S. residents use water "that can contain lead in excess of 15 ppb". In Washington, DC these concerns have led to a $408 million program carried out since 2004 to replace lead service connections to about 35,000 homes. The effectiveness of the program has, however, been put in question in 2008 by WASA, the city's utility. In 2016, more than 5,000 drinking water systems were found to be in violation of the EPA's lead and copper rule.
Substances for which there are no federal standardsEdit
EPA maintains the Contaminant Candidate List (CCL), a list of substances which are being considered for possible regulation in the drinking water program. In an effort to assess the importance of certain substances as contaminants, the National Primary Drinking Water Regulations have required some public water systems to monitor for some of those substances.
Perfluorooctanoic acid (PFOA) is a synthetic perfluorinated carboxylic acid and fluorosurfactant. It has been used in the manufacture of such prominent consumer goods as polytetrafluoroethylene (PTFE; Teflon and similar products). PFOA has been manufactured since the 1940s in industrial quantities. PFOA persists indefinitely in the environment. It is a toxicant and carcinogen in animals. PFOA has been detected in the blood of more than 98% of the general US population in the low and sub-parts per billion (ppb) range, and levels are higher in chemical plant employees and surrounding subpopulations.
In the United States there are no federal drinking water standards for PFOA, PFOS or PFNA (collectively referred to as perfluorinated alkylated substances or PFAS) as of late 2018. EPA began requiring public water systems to monitor for PFOA and PFOS in 2012, and published drinking water health advisories, which are non-regulatory technical documents, in 2016. EPA has not announced whether it will develop a National Primary Drinking Water Regulation for these contaminants.
In November 2017 the State of New Jersey announced plans to develop its own drinking water standards for PFOA. New Jersey published a standard for PFNA in September 2018, the first state to do so. The state set the MCL at 13 parts per trillion (ppt). Other states that have issued PFAS standards include Michigan, New York and Vermont.
Methyl tert-butyl ether (MTBE) is used as a gasoline additive, as well as in various industrial manufacturing processes. The compound has contaminated groundwater and soil across the U.S., and its use has been banned in some states, including California and New York. (See MTBE controversy.) EPA included MTBE on its first Contaminant Candidate List, published in 1998, but has not announced whether it will develop a regulation.
Perchlorate has been detected in public drinking water supplies of over 11 million people in 22 states at concentrations of at least 4 parts per billion (ppb). Above a certain concentration perchlorate alters the production of thyroid hormones by the body, chemicals that are essential for proper development of the fetus and for normal metabolic functioning of the body. According to patient advocate and writer Mary Shomon, people with thyroid conditions, as well as pregnant women and their fetuses are particularly at risk. However, according to the Perchlorate Information Bureau, an industry-supported group, sound scientific and medical research shows that the low levels of perchlorate being detected in drinking water are not dangerous to human health. Still according to the same source, these studies on adults, newborns and children provide reason to believe that low levels of perchlorate (even at levels many times higher than the minute amounts being found in some drinking water supplies) also have no measurable effect on pregnant women or fetuses.
One source of perchlorate in drinking water is the past production of solid rocket propellants using perchlorate, combined with poor disposal practices. Industrial accidents and agricultural fertilizers are also suspected as sources of contamination of drinking water by perchlorate. Perchlorate is also found in breast milk at significant levels, possibly attributable to perchlorate in drinking water and foods. The challenge of defining an acceptable level of perchlorate in drinking water sets two opposing groups with significantly different views against each other. In a draft risk assessment made in 2002, EPA suggested that levels higher than 1 part per billion (ppb) pose a health risk. In contrast, the Defense Department contended that perchlorate at 200 ppb has no lasting effect on humans. Perchlorate is one of only four of the seventy chemicals for which EPA has set public health goals that have a safety factor of 10, rather than the usual safety factors of 100 or 1000.:21 In 2004 eight states had non-binding advisories for perchlorate in drinking water, ranging from 1 to 18 ppb. Only two states—Massachusetts and California—set legally binding maximum contaminant levels on the allowable amount of perchlorate in drinking water, at 2 ppb and 6 ppb respectively.
EPA issued an "Interim Health Advisory" for perchlorate in 2009, while it continued to evaluate whether to issue regulatory standards. In 2011 the agency announced that it would develop regulations for perchlorate. In 2016 a federal district court in New York issued a consent decree requiring EPA to issue a proposed rule for perchlorate in October 2018, and a final rule in December 2019. In late 2018 EPA requested that the court grant a six month extension of the proposed rule deadline.
Many pharmaceutical substances are not regulated under the Safe Drinking Water Act. They have been found in tiny concentrations in the drinking water of several US cities affecting at least 41 million Americans, according to a five-month inquiry by the Associated Press published in March 2008. According to the AP report, researchers do not yet understand the exact risks from decades of persistent exposure to random combinations of low levels of pharmaceuticals.
Pharmaceuticals are included in a broader group of substances currently being studied by EPA, "Pharmaceuticals and Personal Care Products (PPCPs)." This group includes classes of common consumer products such as cosmetics, fragrances, vitamins and sunscreen products.
EPA proposed regulations for radon in 1991 and 1999. In 2010 it was reported that EPA had not finalized the proposal due to concerns raised by some utilities about high costs for controlling radon. However, nine states had issued their own radon guidelines.
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