Drinking water that is supplied through a tap (tap water)
Drinking water orpotable water iswater that is safe foringestion, either whendrunk directly in liquid form or consumed indirectly throughfood preparation. It is often (but not always) supplied through taps, in which case it is also calledtap water.
The amount of drinking water required to maintain good health varies, and depends on physical activity level, age, health-related issues, and environmental conditions.[1][2] For those who work in a hot climate, up to 16 liters (4.2 U.S. gal) a day may be required.[1]
About 1 to 2 billion (or more) people lack safe drinking water.[3] Water cancarry vectors of disease and is a major cause of death and illness worldwide.[4] Developing countries are most affected by unsafe drinking water.
Drinking watervending machines inThailand. One liter of potable water is sold (into the customer's own bottle) for1 baht.Diagram of water well typesSimplified diagram of a water supply network
The most efficient and convenient way to transport and deliver potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $200 billion a year. Leakage of untreated and treated water from pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems.[8]
Tap water, delivered by domesticwater systems refers to water piped to homes and delivered to atap or spigot.
In the United States, the typical water consumption per capita, at home, is 69.3 U.S. gallons (262 L; 57.7 imp gal) of water per day.[9][10] Of this, only 1% of the water provided by public water suppliers is for drinking and cooking.[11] Uses include (in decreasing order) toilets, washing machines, showers, baths, faucets, and leaks.
Total renewable water resources per capita in 2020
The recommended daily amount of drinking water for humans varies.[12] It depends on activity, age,health, and environment. In the United States, theAdequate Intake for total water, based on median intakes, is 4.0 litres (141 imp fl oz; 135 US fl oz) per day for males older than 18, and 3.0 litres (106 imp fl oz; 101 US fl oz) per day for females over 18; it assumes about 80% from drink and 20% from food.[13] TheEuropean Food Safety Authority recommends 2.0 litres (70 imp fl oz; 68 US fl oz) of total water per day for women and 2.5 litres (88 imp fl oz; 85 US fl oz) per day for men.[14]
The qualitative and quantitative aspects of drinking water requirements ondomesticated animals are examined within the context ofanimal husbandry. For example, a farmer might plan for 35 U.S. gallons (130 L) per day for adairy cow, a third of that for ahorse, and a tenth of that for ahog.[15]
However, relatively few studies have been focused on the drinking behavior of wild animals.
According to the World Health Organization's 2017 report,safedrinking water is water that "does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages".[16]: 2
Example for physical and chemical parameters measured in drinking water samples in Kenya and Ethiopia as part of asystematic review of published literature[20]
Physical and chemical parameters includeheavy metals, traceorganic compounds,total suspended solids, andturbidity. Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites andarsenic can have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.
Pesticides are also potential drinking water contaminants of the categorychemical contaminants. Pesticides may be present in drinking water in low concentrations, but thetoxicity of the chemical and the extent of human exposure are factors that are used to determine the specific health risk.[21]
Perfluorinated alkylated substances (PFAS) are a group of synthetic compounds used in a large variety of consumer products, such asfood packaging, waterproof fabrics, carpeting and cookware. PFAS are known to persist in the environment and are commonly described aspersistent organic pollutants. PFAS chemicals have been detected in blood, both humans and animals, worldwide, as well as in food products, water, air and soil.[22] Animal testing studies with PFAS have shown effects on growth and development, and possibly effects on reproduction, thyroid, the immune system and liver.[23] As of 2022 the health impacts of many PFAS compounds are not understood. Scientists are conducting research to determine the extent and severity of impacts from PFAS on human health.[24] PFAS have been widely detected in drinking water worldwide and regulations have been developed, or are under development, in many countries.[25]
Drinking water quality standards describes the qualityparameters set for drinking water. Water may contain manyharmful constituents, yet there are no universally recognised and accepted international standards for drinking water. Even where standards do exist, the permitted concentration of individual constituents may vary by up to ten times from one set of standards to another. Many countries specify standards to be applied in their own country. In Europe, this includes theEuropean Drinking Water Directive[26] and in the United States, theUnited States Environmental Protection Agency (EPA) establishes standards as required by theSafe Drinking Water Act. China adopted its own drinking water standard GB3838-2002 (Type II) enacted byMinistry of Environmental Protection in 2002.[27] For countries without a legislative or administrative framework for such standards, theWorld Health Organization (WHO) publishes guidelines on the standards that should be achieved.[28]
Where drinking water quality standards do exist, most are expressed as guidelines or targets rather than requirements, and very few water standards have any legal basis or, are subject to enforcement.[29] Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the United States,[30] which require legal compliance with specific standards. In Europe, this includes a requirement for member states to enact appropriate local legislation to mandate the directive in each country. Routine inspection and, where required, enforcement is enacted by means of penalties imposed by theEuropean Commission on non-compliant nations.
One of the main causes for contaminated drinking water in developing countries is lack of sanitation and poor hygiene. For this reason, the quantification of theburden of disease from consuming contaminated drinking water usually looks at water, sanitation and hygiene aspects together. Theacronym for this isWASH - standing forwater, sanitation and hygiene.
TheWHO has investigated which proportion of death and disease worldwide can be attributed to insufficient WASH services. In their analysis they focus on the following four health outcomes:diarrhea,acute respiratory infections,malnutrition, and soil-transmittedHelminthiasis (STHs).[35]: vi These health outcomes are also included as an indicator for achievingSustainable Development Goal 3 ("Good Health and Well-being"): Indicator 3.9.2 reports on the "mortality rate attributed to unsafe water, sanitation, and lack of hygiene".
In 2023,WHO summarized the available data with the following key findings: "In 2019, use of safe WASH services could have prevented the loss of at least 1.4 million lives and 74 milliondisability-adjusted life years (DALYs) from four health outcomes. This represents 2.5% of all deaths and 2.9% of all DALYs globally."[35]: vi Of the four health outcomes studied, it wasdiarrheal disease that had the most striking correlation, namely the highest number of "attributableburden of disease": over 1 million deaths and 55 million DALYs from diarrheal diseases were linked with lack of WASH. Of these deaths, 564,000 deaths were linked to unsafe sanitation in particular.
Poverty often leads to unhygienic living conditions, as in this community in the Indian Himalayas. Such conditions promote contraction of diarrheal diseases, as a result of contaminated drinking water, poorsanitation andhygiene.
Diarrhea is primarily transmitted throughfecal–oral routes. In 2011, infectious diarrhea resulted in about 0.7 million deaths in children under five years old and 250 million lost school days.[36][37] This equates to about 2000 child deaths per day.[38] Children suffering from diarrhea are more vulnerable to becomeunderweight (due tostunted growth).[39][40] This makes them more vulnerable to other diseases such asacute respiratory infections andmalaria. Chronic diarrhea can have a negative effect on child development (both physical andcognitive).[41]
Numerous studies have shown that improvements in drinking water and sanitation (WASH) lead to decreased risks of diarrhea.[42] Such improvements might include for example, the use ofwater filters, provision of high-quality piped water andsewer connections.[42] Diarrhea can be prevented - and the lives of 525,000 children annually be saved (estimate for 2017) - byimproved sanitation, clean drinking water, andhand washing with soap.[43] In 2008 the same figure was estimated as 1.5 million children.[44]
Sixty million people are estimated to have been poisoned by well water contaminated by excessivefluoride, which dissolved from granite rocks. The effects are particularly evident in the bone deformations of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia. Although helpful for dental health in low dosage, fluoride in large amounts interferes with bone formation.[45]
Long-term consumption of water with high fluoride concentration (> 1.5 ppm F) can have serious undesirable consequences such asdental fluorosis, enamel mottle andskeletal fluorosis, bone deformities in children. Fluorosis severity depends on how much fluoride is present in the water, as well as people's diet and physical activity. Defluoridation methods include membrane-based methods, precipitation, absorption, and electrocoagulation.[46]
WalkertonE. coli outbreak (Escherichia coli O157:H7 andCampylobacter contamination of water supply in Walkerton, Ontario, Canada in 2000). In 2000, anE. coli outbreak occurred inWalkerton, Ontario, Canada. Seven people died from drinking contaminated water. Hundreds suffered from the symptoms of the disease.[49]
Flint water crisis (lead andLegionella contamination of water supply in Flint, Michigan, United States, started in 2014)[citation needed]
In 1998, an outbreak oftyphoid fever in northern Israel, which was associated with the contaminated municipal water supply[51]
In 1997, 369 cases ofcryptosporidiosis occurred, caused by a contaminated fountain in the Minnesota zoo. Most of the sufferers were children[52]
In 1998, a non-chlorinated municipal water supply was blamed for acampylobacteriosis outbreak in northern Finland[53]
In 2000, agastroenteritis outbreak that was brought by a non-chlorinated community water supply, in southern Finland[54]
In 2004, contamination of the community water supply, serving the Bergen city centre of Norway, was later reported after the outbreak of waterbornegiardiasis[55]
In 2007, contaminated drinking water was pinpointed which had led to the outbreak of gastroenteritis with multipleaetiologies in Denmark[56]
In 1993, a fluoride poisoning outbreak resulting from overfeeding of fluoride, in Mississippi[57]
In 2019, electrictransformer oil entered the water supply for the city ofUummannaq in Greenland. A cargo ship in harbour was able to maintain a minimum supply to the city for two days until the mains supply was restored and flushing of all the pipework was started.[58]
Most water requires some treatment before use; even water from deep wells or springs. The extent of treatment depends on the source of the water. Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs.[59] Only a few large urban areas such asChristchurch,New Zealand have access to sufficiently pure water of sufficient volume that no treatment of the raw water is required.[60]
In emergency situations when conventional treatment systems have been compromised, waterborne pathogens may be killed or inactivated byboiling[61] but this requires abundant sources of fuel, and can be very onerous on consumers, especially where it is difficult to store boiled water in sterile conditions. Other techniques, such as filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries,[62] but these suffer from the same problems as boiling methods.
Another type of water treatment is calleddesalination and is used mainly in dry areas with access to large bodies of saltwater.
In the event of contamination of drinking water, government officials typically issue an advisory regarding water consumption. In the case ofbiological contamination, residents are usually advised to boil their water before consumption or to use bottled water as an alternative. In the case ofchemical contamination, residents may be advised to refrain from consuming tap water entirely until the matter is resolved.
The ability of point of use (POU) options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. Technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest.
The current priority of the proponents of POU treatment is to reach large numbers of low-income households on a sustainable basis. Few POU measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years.
Solar water disinfection is a low-cost method of purifying water that can often be implemented with locally available materials.[64][65][66][67] Unlike methods that rely onfirewood, it has a low impact on the environment.
World map forSDG 6 Indicator 6.1.1 in 2022: "Proportion of population using safely managed drinking water services"Population in survey regions living without safely managed drinking water as reported by the WHO/UNICEF JMP[6]
According to theWorld Health Organization (WHO), "access to safe drinking-water is essential to health, a basic human right and a component of effective policy for health protection."[16]: 2 In 1990, only 76 percent of the global population had access to drinking water. By 2015 that number had increased to 91 percent.[75] In 1990, most countries in Latin America, East and South Asia, and Sub-Saharan Africa were well below 90%. In Sub-Saharan Africa, where the rates are lowest, household access ranges from 40 to 80 percent.[75] Countries that experience violent conflict can have reductions in drinking water access: One study found that a conflict with about 2,500 battle deaths deprives 1.8% of the population of potable water.[76]
Typically indeveloped countries, tap water meetsdrinking water quality standards, even though only a small proportion is actually consumed or used in food preparation. Other typical uses for tap water include washing, toilets, andirrigation.Greywater may also be used for toilets or irrigation. Its use for irrigation however may be associated with risks.[32]
Globally, by 2015, 89% of people had access to water from a source that is suitable for drinking – calledimproved water sources.[32] Insub-Saharan Africa, access to potable water ranged from 40% to 80% of the population. Nearly 4.2billion people worldwide had access to tap water, while another 2.4 billion had access towells or public taps.[32]
By 2015, 5.2 billion people representing 71% of the global population used safely managed drinking water services.[77] As of 2017, 90% of people having access to water from a source that is suitable for drinking – calledimproved water source – and 71% of the world could access safely managed drinking water that is clean and available on-demand.[32] Estimates suggest that at least 25% of improved sources contain fecal contamination.[78] 1.8 billion people still use an unsafe drinking water source which may be contaminated byfeces.[32] This can result ininfectious diseases, such asgastroenteritis,cholera, andtyphoid, among others.[32] Reduction of waterborne diseases and development of safe water resources is a majorpublic health goal in developing countries. In 2017, almost 22 million Americans drank from water systems that were in violation of public health standards, which could contribute to citizens developingwater-borne illnesses.[79][full citation needed] Safe drinking water is anenvironmental health concern.Bottled water is sold for public consumption in most parts of the world.
Improved sources are also monitored based on whether water is available when needed (5.8 billion people), located on premises (5.4 billion), free from contamination (5.4 billion), and within a 30-minute round trip.[77]: 3 While improved water sources such as protected piped water are more likely to provide safe and adequate water as they may prevent contact with human excreta, for example, this is not always the case.[75] According to a 2014 study, approximately 25% of improved sources contained fecal contamination.[78]
The population in Australia, New Zealand, North America and Europe have achieved nearly universal basic drinking water services.[77]: 3
Because of the high initial investments, many less wealthy nations cannot afford to develop or sustain appropriate infrastructure, and as a consequence people in these areas may spend a correspondingly higher fraction of their income on water.[80] 2003 statistics from El Salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. In the United Kingdom, authorities define spending of more than 3% of one's income on water as a hardship.[81]
Access to safe drinking water is indicated by safe water sources. These improved drinking water sources include household connection, publicstandpipe,borehole condition, protected dug well, protected spring, and rain water collection. Sources that do not encourage improved drinking water to the same extent as previously mentioned include: unprotected wells, unprotected springs, rivers or ponds, vender-provided water, bottled water (consequential of limitations in quantity, not quality of water), and tanker truck water. Access to sanitary water comes hand in hand with access toimproved sanitation facilities for excreta, such as connection to public sewer, connection to septic system, or apit latrine with a slab or water seal.[84]
According to this indicator on improved water sources, the MDG was met in 2010, five years ahead of schedule. Over 2 billion more people used improved drinking water sources in 2010 than did in 1990. However, the job is far from finished. 780 million people are still without improved sources of drinking water, and many more people still lack safe drinking water. Estimates suggest that at least 25% of improved sources contain fecal contamination[78] and an estimated 1.8 billion people globally use a source of drinking water that suffers from fecal contamination.[85] The quality of these sources varies over time and often gets worse during the wet season.[86] Continued efforts are needed to reduce urban-rural disparities and inequities associated with poverty; to dramatically increase safe drinking water coverage in countries in sub-Saharan Africa and Oceania; to promote global monitoring of drinking water quality; and to look beyond the MDG target towards universal coverage.[87]
Guidelines for the assessment and improvement of service activities relating to drinking water have been published in the form ofdrinking water quality standards such as ISO 24510.[88]
For example, theEU sets legislation on water quality.Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy, known as the water framework directive, is the primary piece of legislation governing water.[89] This drinking water directive relates specifically to water intended for human consumption. Each member state is responsible for establishing the required policing measures to ensure that the legislation is implemented. For example, in the UK theWater Quality Regulations prescribe maximum values for substances that affect wholesomeness and theDrinking Water Inspectorate polices the water companies.
To improve water quality, Japan's Ministry of Health revised its water quality standards, which were implemented in April 2004.[90] Numerous professionals developed the drinking water standards.[90] They also determined ways to manage the high quality water system. In 2008, improved regulations were conducted to improve the water quality and reduce the risk of water contamination.[90]
The Water Services Act 2021 brought Taumata Arowai' into existence as the new regulator of drinking water and waste water treatment in New Zealand. Initial activities including the establishment of a national register of water suppliers and establishing a network of accredited laboratories for drinking water and waste water analysis[91]
Singapore is a significant importer of water from neighbouringMalaysia but also has made great efforts to reclaim as much used water as possible to ensure adequate provision for the very crowded city-state. Their reclaimed water is marketed asNEWater. Singapore updated its water quality regulation in 2019, setting standards consistent with the WHO recommended standards. Monitoring is undertaken by the Environmental Public Health Department of the Singaporean Government[92]
In England and Wales there are twowater industry regulatory authorities.
Water Services Regulation Authority (Ofwat) is the economic regulator of the water sector; it protects the interests of consumers by promoting effective competition and ensuring that water companies carry out their statutory functions. Ofwat has a management board comprising a chairman, Chief Executive and Executive and Non-Executive members. There is a staff of about 240.[93]
TheDrinking Water Inspectorate (DWI) provides independent assurance that the privatizedwater industry delivers safe, clean drinking water to consumers. The DWI was established in 1990 and comprises a Chief Inspector of Drinking Water and a team of about 40 people.[94] The current standards of water quality are defined in Statutory Instrument 2016 No. 614 the Water Supply (Water Quality) Regulations 2016.[95]
The functions and duties of the bodies are formally defined in the Water Industry Act 1991 (1991 c. 56) as amended by the Water Act 2003 (2003 c. 37) and the Water Act 2014 (2014 c. 21).[96]
In Scotland water quality is the responsibility of independent Drinking Water Quality Regulator (DWQR).[97]
In Northern Ireland the Drinking Water Inspectorate (DWI) regulates drinking water quality of public and private supplies.[98] The current standards of water quality are defined in the Water Supply (Water Quality) Regulations (Northern Ireland) 2017.[99]
Drinking water quality in the United States is generally safe. In 2016, over 90 percent of the nation's community water systems were in compliance with all publishedU.S. Environmental Protection Agency (US EPA) standards.[100] Over 286 million Americans get their tap water from a community water system. Eight percent of the community water systems—large municipal water systems—provide water to 82 percent of the US population.[101] TheSafe Drinking Water Act requires the US EPA to set standards for drinking water quality inpublic water systems (entities that provide water for human consumption to at least 25 people for at least 60 days a year).[102] Enforcement of the standards is mostly carried out by state health agencies.[103] States may set standards that are more stringent than the federal standards.[104]
Despite improvements in water quality regulations, disparities in access to clean drinking water persist in marginalized communities. A 2017 study by the Natural Resources Defense Council (NRDC) highlighted that rural areas and low-income neighborhoods are disproportionately affected by water contamination, often due to aging infrastructure and inadequate funding for water systems.[105] These inequities underscore the need for more targeted investment and stronger enforcement of the Safe Drinking Water Act in vulnerable regions.
Drinking water quality in the U.S. isregulated by state and federal laws and codes, which setmaximum contaminant levels (MCLs) and Treatment Technique requirements 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 publishConsumer Confidence Reports.[106]
In drinking water access, quality and quantity are both important parameters but the quantity is often prioritized.[48] Throughout human history, water quality has been a constant and ongoing challenge. Certain crises have led to major changes in knowledge, policy, and regulatory structures. The drivers of change can vary: thecholera epidemic in the 1850s in London ledJohn Snow to further our understanding ofwaterborne diseases. However,London's sanitary revolution was driven by political motivations and social priorities before the science was accepted.[48]
^abAnn C. Grandjean (August 2004)."3"(PDF).Water Requirements, Impinging Factors, & Recommended Intakes. World Health Organization. pp. 25–34.Archived(PDF) from the original on 22 February 2016. This 2004 article focuses on the USA context and uses data collected from the US military.
^Schardt, David (2000)."Water, Water Everywhere". Washington, D.C.: Center for Science in the Public Interest. Archived fromthe original on 16 May 2009.
^Mayer, P.W.; DeOreo, W.B.; Opitz, E.M.; Kiefer, J.C.; Davis, W.Y.; Dziegielewski, B.; & Nelson, J.O., 1999. Residential End Uses of Water. AWWARF and AWWA, Denver.
^William B. DeOreo, Peter Mayer, Benedykt Dziegielewski, Jack Kiefer. 2016. Residential End Uses of Water, Version 2. Water Research Foundation. Denver, Colorado.
^Ann C. Grandjean (August 2004)."3"(PDF).Water Requirements, Impinging Factors, & Recommended Intakes. World Health Organization. pp. 25–34.Archived(PDF) from the original on 22 February 2016. This 2004 article focuses on the USA context and uses data collected from the US military.
^"Drinking Water and Pesticides".National Pesticide Information Center. Corvallis, OR: Oregon State University. 16 September 2021.Archived from the original on 16 September 2022. Retrieved6 January 2022.
^"PFAS Explained". EPA. 18 October 2021.Archived from the original on 22 December 2022. Retrieved7 January 2022.
^Pearce, Fred (2006).When the Rivers Run Dry: Journeys Into the Heart of the World's Water Crisis. Toronto: Key Porter.ISBN978-1-55263-741-8.
^Ahuja, Satinder (2018).Advances in Water Purification Techniques: Meeting the Needs of Developed and Developing Countries. San Diego: Elsevier.ISBN978-0-12-814791-7.OCLC1078565849.
^Hayes EB, Matte TD, O'Brien TR, et al. (May 1989). "Large community outbreak of cryptosporidiosis due to contamination of a filtered public water supply".N. Engl. J. Med.320 (21):1372–76.doi:10.1056/NEJM198905253202103.PMID2716783.
^Egoz N, Shihab S, Leitner L, Lucian M (November 1988). "An outbreak of typhoid fever due to contamination of the municipal water supply in northern Israel".Isr. J. Med. Sci.24 (11):640–43.PMID3215755.
^Pizzo G, Piscopo MR, Pizzo I, Giuliana G (September 2007). "Community water fluoridation and caries prevention: a critical review".Clinical Oral Investigations.11 (3):189–193.doi:10.1007/s00784-007-0111-6.PMID17333303.S2CID13189520.
^Taricska JR, Wang LK, Hung YT, Li KH (2006). "Fluoridation and Defluoridation". In Wang LK, Hung YT, Shammas NK (eds.).Advanced Physicochemical Treatment Processes. Handbook of Environmental Engineering 4. Humana Press. pp. 293–315.doi:10.1007/978-1-59745-029-4_9.ISBN978-1-59745-029-4.
^Guidelines for Drinking-water Quality, 4th Edition WHO, 2011.ISBN978-9241548151. p. 168, 175, 372 and see also pp 370–373. See also J. Fawell, et alFluoride in Drinking-water. WHO, 2006. p. 32. Quote: "Concentrations in drinking-water of about 1 mg l–1 are associated with a lower incidence of dental caries, particularly in children, whereas excess intake of fluoride can result in dental fluorosis. In severe cases this can result in erosion of enamel. The margin between the beneficial effects of fluoride and the occurrence of dental fluorosis is small and public health programmes seek to retain a suitable balance between the two"
^U.S. Environmental Protection Agency. Report on the environment: drinking water. Available at:https://cfpub.epa.gov. Accessed March 3, 2023.Archived March 10, 2023, at theWayback Machine
^ISO 24510 Activities relating to drinking water and wastewater services. Guidelines for the assessment and for the improvement of the service to users
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