Jump to content

Drinking water

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Velella (talk | contribs) at 22:34, 5 November 2008 (→Access to drinking water: more minor mods- this article is in dire need of a major overhaul.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Tap water
Mineral Water

Drinking water is water that is of sufficiently high quality that it can be drunk without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries the water supplied to households, commerce and industry is all of Drinking water standard even though only a very small proportion is actually drunk or used in food preparation.

Over large parts of the world, humans drink water that contains disease vectors or pathogens or contain unacceptable levels of dissolved contaminants or solids in suspension. Such waters are not potable water and drinking such waters or using them in cooking leads to widespread acute and chronic illness and is a major cause of death in many countries.

Typically, water supply networks deliver potable water, whether it is to be used for drinking, washing or landscape irrigation. One counterexample is urban China, where drinking water can optionally be delivered by a separate tap.

Water quality and contaminants

Further information: Water quality
Further information: Appropriate technology § Drinking water

Throughout most of the world the most common contamination of raw water sources is from human sewage and in particular human faecal pathogens and parasites. In 2006, waterborne diseases were estimated to cause 1.8 million deaths each year while about 1.1 billion people lacked proper drinking water.[1]. It is clear that people in the developing world need to have access to good quality water in sufficient quantity, purification technology and availability and distribution systems for water. In many parts of the world the only sources of water are from small streams often directly contaminated by sewage. However, even where wells are used this does not eliminate the risk of contamination .

Most water requires some type of treatment before use, even water from deep wells or springs. The extend 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.[2]

The most reliable way to kill microbial pathogenic agents is to heat water to a rolling boil[3] but this requires abundant sources of fuel and is very onerous on the households especially where it is difficult to store boiled water in sterile conditions. Other techniques, such as varying forms of 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.[4]

Over the past decade, an increasing number of field-based studies have been undertaken to determine the success of POU measures in reducing waterborne disease. The ability of 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.

Parameters for drinking water quality typically fall under two categories: chemical/physical and microbiological. Chemical/physical parameters include heavy metals, trace organic compounds, total suspended solids (TSS), and turbidity. Microbiological parameters include Coliform bacteria, E. coli, and specific pathogenic species of bacteria (such as cholera-causing Vibrio cholerae), viruses, and protozoan parasites.

Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites and arsenic may have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.

Originally, fecal contamination was determined with the presence of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like E. Coli) serves as an indication of contamination by sewage. Additional contaminants include protozoan oocysts such as Cryptosporidium sp., Giardia lambia, Legionella, and viruses (enteric).[5] Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk.

Access to drinking water

Further information: Water resources
Only forty-six percent of people in Africa have safe drinking water.
File:Condensationbag.jpg
Gathering water through the use of a bag is a much employed survival technique
Gathering water through the use of a pit (solar still)is another much employed survival technique
Runoff water may also be obtained from hillsides
Drinking water vending machines in Thailand. One litre of purified water is sold (into the customer's own bottle) for 1 baht
A home made water filter is often employed for making drinking water

Earth's surface consists of 70% water. Water is available almost everywhere if proper methods are used to get it. Sources where water may be obtained include:

As a country’s economy becomes richer, a larger percentage of its people tend to have access to drinking water and sanitation. Access to drinking water is measured by the number of people who have a reasonable means of getting an adequate amount of water that is safe for drinking, washing, and essential household activities.

As of the year 2006 (and pre-existing for at least three decades), there is a substantial shortfall in availability of potable water in less developed countries, principally because of migration from the countryside to urban areas in countries with low average rainfall and limited infrastructure. As of the year 2000, 27 percent of the populations of lesser developed countries did not have access to safe drinking water[6]. Implications for disease propagation are significant. Many nations have water quality regulations for water sold as drinking water, although these are often not strictly enforced outside of the developed world. The World Health Organization sets international standards for drinking water. A broad classification of drinking water safety worldwide can be found in Safe Water for International Travellers.

It reflects the health of a country’s people and the country’s capacity to collect, clean, and distribute water to consumers. According to the United Nations' World Health Organization (WHO) more than one billion people in low and middle-income countries lack access to safe water for drinking, personal hygiene and domestic use. These numbers represent more than 20 percent of the world’s people. In addition, close to 3 billion people did not have access to adequate sanitation facilities. (For details see data on the website of the Joint Monitoring Program (JMP) on water and sanitation of WHO and UNICEF.)

While the occurrence of waterborne diseases in developed countries is generally low due to a generally good system of water treatment, distribution and monitoring, waterborne diseases are among the leading causes of morbidity and mortality in low- and middle-income countries, frequently called developing countries.

The main reason for poor access to safe water is the inability to finance and to adequately maintain the necessary infrastructure. Overpopulation and scarcity of water resources are contributing factors.

Many other countries also lack in the amount of safe drinking water that they need to survive. Some of the countries have less than twenty percent of the population that has access to safe drinking water. For example in Africa, with more than 700 million people, only forty-six percent of people have safe drinking water. The more populous Asia Pacific region with over three billion people, eighty percent of whom with access to drinking water, still leaves over 600 million people without access to safe drinking water.[2]

The lack of water and the lack of hygiene is one of the biggest problems that many poor countries have encountered in progressing their way of living. The problem has reached such endemic proportions that 2.2 million deaths per annum occur from unsanitary water - ninety percent of these are children under the age of five. [3] One program developed to help people gain access to safe drinking water is the Water Aid program. Working in 17 countries to help provide water, Water Aid is useful in helping the sanitation and hygiene education to some of the world's poorest people.[4] Solar water disinfection is a low-cost method of purifying water that can often be implemented with locally available materials.[7] [8] [9] [10] Unlike methods that rely on firewood, it has low impact on the environment.

Table 2: Percentage of population with access to safe drinking water (2000) [11]
Country %   Country %   Country %   Country %   Country %
Albania 97   Algeria 89   Azerbaijan 78   Brazil 87   Chile 93
China 75   Cuba 91   Egypt 97   India 84   Indonesia 78
Iran 92   Iraq 85   Kenya 57   Mexico 88   Morocco 80
Peru 80   Philippines 86   South Africa 86   South Korea 92   Sudan 67
Syria 80   Turkey 82   Uganda 52   Venezuela 83   Zimbabwe 83
Note: All industrialized countries (as listed by UNICEF) with data available are at 100%.

In the US, the typical nonconserving single family home uses 69.3 gallons of water per capita per day. These figures are concerning in some parts of the country where water supplies are dangerously low due to drought, particularly in the West and the South East region of the U.S [12].

Metabolism

Main article: Fluid balance

Water is necessary for all life on Earth. Humans can survive for several weeks without food, but for only a few days without water. A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, perspiration and urination. In terms of mineral nutrients intake, it is unclear what the drinking water contribution is. However, inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust. Treatment processes also lead to the presence of some mineral nutrients. Examples include fluoride, calcium, zinc, manganese, phosphate, and sodium compounds.[13] Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example sodium, potassium and chloride are common chemicals found in small quantities in most waters, and these elements play a role (not necessarily major) in body metabolism. Other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels. Water is essential for the growth and maintenance of our bodies, as it is involved in a number of biological processes.

Requirement

The exact amount of water a human needs is highly individual, as it depends on the condition of the subject, the amount of physical exercise, and on the environmental temperature and humidity.[14] In the US, the reference daily intake (RDI) for water is 3.7 litres per day for human males older than 18, and 2.7 litres for human females older than 18[15] including water contained in food, beverages, and drinking water. Food contributes 0.5 to 1 litre, and the metabolism of protein, fat, and carbohydrates produces another 0.25 to 0.4 litres[16], which means that 2 to 3 litres of water for men and 1 to 2 litres of water for women should be taken in as fluid in order to meet the RDI. Because in general, RDI values incorporate a safety margin to account for individual variations, it does not mean that this amount is necessary for every person. The folk wisdom that everyone should drink two litres (68 ounces, or about eight 8-oz glasses) of water per day is not supported by scientific research. Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day.[17] [18] [19] For example, people in hotter climates will require greater water intake than those in cooler climates. An individual's thirst provides a better guide for how much water they require rather than a specific, fixed number. A more flexible guideline is that a normal person should urinate 4 times per day, and the urine should be a light yellow color. Profuse sweating can increase the need for electrolyte (salt) replacement. Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal.

The human kidneys will normally adjust to varying levels of water intake. If a person suddenly increases water intake, the kidneys will produce more diluted urine, even if the person did not happen to consume water excessively. The kidneys will require time to adjust to the new water intake level. This can cause someone who drinks a lot of water to become dehydrated more easily than someone who routinely drinks less. Survival classes recommend that someone who expects to be in an environment with little water (such as a desert), to not drink water excessively, but rather to drink gradually decreasing amounts for several days before their trip to accustom the kidneys to making concentrated urine. Not using this method can, and has been known to be, fatal.[20]

Indicators of Safe Drinking Water

Access to safe drinking water is indicated by the number of people using proper sanitary sources. These improved drinking water sources include household connection, public standpipe, borehole condition, protected dug well, protected spring, and rain water collection. Sources that don't encourage improved drinking water to the same extent as previously mentioned include: unprotected well, unprotected spring, 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 ^^ to improved sanitation facilities for excreta. These facilities include connection to public sewer, connection to septic system, pour-flush latrine, and ventilated improved pit latrine. Unimproved sanitation facilities are: public or shared latrine, open pit latrine, or bucket latrine[21].

Diarrhea as a major health effect among children

Diarrhoeal diseases cause ninety percent of all deaths of children under five years old in developing countries. Malnutrition, especially protein-energy malnutrition, can decrease the children's resistance to infections, including water-related diarrhoeal diseases. In 2000-2003, 769,000 children under five years old in sub-Saharan Africa died each year from diarrhoeal diseases. As a result of only thirty-six percent of the population in the sub-Saharan region having access to proper means of sanitation, more than 2000 children's lives are lost every day. In south Asia, 683,000 children under five years old died each year from diarrhoeal disease from 2000-2003. During the same time period, in developed countries, 700 children under five years old died from diarrhoeal disease. Improved water supply reduces diarrhea morbidity by twenty-five percent and improvements in drinking water through proper storage in the home and chlorination reduces diarrhea episodes by thirty-nine percent[22].

Plans to improve availability of drinking water

One of the Millennium Development Goals (MDGs) set by the UN includes environmental sustainability. In 2004, only forty-two percent of people in rural areas had access to clean water. Sixty-three percent of the population in sub-Saharan Africa lacked access to basic sanitation facilities (hardly down from the sixty-eight percent in 1990). The effects of climate change add more distress to sub-Saharan Africa. The Intergovernmental Panel on Climate Change estimates that 75-250 million people will have to cope with additional limitations to water access. The results could be terrible for the livelihoods of the disadvantaged and rural economies. Currently the UN is not on schedule with their plans and estimates that their intended goal will not be reached by 2015[23].

Drinking water regulation

In the United States, the Environmental Protection Agency sets standards for tap and public water, while the Food and Drug Administration regulates bottled water as a food product under the Federal Food, Drug, and Cosmetic Act (FFDCA). Potable water quality is defined by the Safe Drinking Water Act (SDWA). [24] However, bottled water is not necessarily more pure, or more tested, than public tap water.[25] EPA standards for safe public water systems are based on the Safe Drinking Water Act.[26]

For more information regarding United States regulation of bottled water production, see the Code of Federal Regulations, 21 CFR Part 129.[27]

United States' Bottled water classifications

Bottled water manufacturers in the United States must ensure that their products meet the FDA established standard of identity for bottled water products.[28] A bottled water product identified under a specific category, such as mineral water, spring water, artesian water, etc., must meet requirements established by the government or be considered misbranded.

FDA regulations define identity information for categories of bottled water:[29]

  • drinking water - The lowest common denominator of potable water categories, meeting the basic EPA/FDA standards
  • ground water - The name of water from a subsurface saturated zone that is under a pressure equal to or greater than atmospheric pressure.
  • artesian water, also known as artesian well water - The name of water from a well tapping a confined aquifer in which the water level stands at some height above the top of the aquifer. (Water that will rise above the water table if tapped) Artesian water may be collected with the assistance of external force to enhance the natural underground pressure.
    • How often is "artesian water" tested to meet these standards? The law says there is no mandatory testing, instead: "On request, plants shall demonstrate to appropriate regulatory officials that the water level stands at some height above the top of the aquifer."[30]
  • mineral water - The name of water containing not less than 250 parts per million (ppm) total dissolved solids (TDS), coming from a source tapped at one or more bore holes or springs, originating from a geologically and physically protected underground water source. Mineral water shall be distinguished from other types of water by its constant level and relative proportions of minerals and trace elements at the point of emergence from the source, due account being taken of the cycles of natural fluctuations. No minerals may be added to this water.
  • purified water - The name of water that has been produced by distillation, deionization, reverse osmosis, or other suitable processes and that meets the definition of "purified water" in the United States Pharmacopeia, 23d Revision, January 1, 1995.
    • Alternatively, the water may be called "deionized water" if the water has been processed by deionization, "distilled water" if it is produced by distillation, or "reverse osmosis water" if the water has been processed by reverse osmosis.
  • sparkling water - The name of water that, after treatment and possible replacement of carbon dioxide, contains the same amount of carbon dioxide from the source that it had at emergence from the source.
  • spring water - The name of water derived from an underground formation from which water flows naturally to the surface of the earth.
    • Spring water shall be collected only at the spring or through a bore hole tapping the underground formation feeding the spring. There shall be a natural force causing the water to flow to the surface through a natural orifice. The location of the spring shall be identified.


See also

References

  1. ^ U.S. Centers for Disease Control and Prevention. Atlanta, GA. "Safe Water System: A Low-Cost Technology for Safe Drinking Water." Fact Sheet, World Water Forum 4 Update. March 2006.
  2. ^ Centre for Affordable Water and Sanitation Technology, [http://webmail.cawst.org/documents/Camille/New%20Training%20Materials/HWT%20Manual_Mar%2008.pdf "Household Water Treatment Guide," March 2008.
  3. ^ [1] WHO’s Guidelines for Drinking Water Quality
  4. ^ Clasen, T., Schmidt, W., Rabie, T., Roberts, I., Cairncross, S. Interventions to improve water quality for preventing diarrhoea: a systematic review and meta-analysis. British Medical Journal, doi:10.1136/bmj.39118.489931.BE (published 12 March 2007)
  5. ^ U.S. EPA. "Drinking Water Contaminants: Microorganisms."
  6. ^ I.A. Shiklomanov, Appraisal and Assessment of World Water Resources, Water International 25(1): 11-32 (2000)
  7. ^ Conroy R.M., Meegan M.E., Joyce T., McGuigan K., Barnes J. (1999), Solar disinfection of water reduces diarrhoeal disease, an update, Arch Dis Child, Vol. 81.
  8. ^ Conroy R.M., Meegan M.E., Joyce T.M., McGuigan K.G., Barnes J. (2001) Use of solar disinfection protects children under 6 years from cholera. Arch Dis Child; 85:293-295
  9. ^ Rose A. at al. (2006). Solar disinfection of water for diarrhoeal prevention in Southern India. Arch Dis Child, 91(2): 139-141
  10. ^ Hobbins M. (2003). The SODIS Health Impact Study, Ph.D. Thesis, Swiss Tropical Institute Basel
  11. ^ United Nations Childrens Fund (UNICEF). New York, NY. "Safe Drinking Water." Excerpt from "Progress since the World Summit for Children: A Statistical Review." September 2001.
  12. ^ March 2008, Cashing in on Climate Change, IBISWorld
  13. ^ World Health Organization (WHO). Geneva, Switzerland. Joyce Morrissey Donohue, Charles O. Abernathy, Peter Lassovszky, George Hallberg. "The contribution of drinking-water to total dietary intakes of selected trace mineral nutrients in the United States." Draft, August 2004.
  14. ^ Maton, Anthea bj (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  15. ^ US daily reference intake values
  16. ^ Swedish DFA (in Swedish)
  17. ^ Research debunks health value of guzzling water. Reuters, April 2008.
  18. ^ H. Valtin, Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 × 8"? Am J Physiol Regul Integr Comp Physiol 283: R993-R1004, 2002.
  19. ^ Dan Negoianu and Stanley Goldfarb. Just add water. J. Am. Soc. Nephrol. 19: 1041-1043, 2008.
  20. ^ Man Dies of Thirst During Survival Test, San Francisco Chronicle, May 2, 2007
  21. ^ Meeting the MDG Drinking Water and Sanitation Target: A Mid-Term Assessment of Progress [www.who.int/water_sanitation_health/monitoring/jmp04.pdf]
  22. ^ WHO/UNICEF, Water for life: making it happen
  23. ^ Africa and the Millennium Development Goals [www.un.org/millenniumgoals/docs/MDGafrica07.pdf]
  24. ^ June 25, 1938, ch. 675, 52 Stat. 1040; 21 U.S.C. § 301 et seq.
  25. ^ U.S. EPA. Washington, DC. "Ground water and drinking water - Frequently asked questions."
  26. ^ Pub.L. 93-523; 42 U.S.C. § 300f et seq. December 16, 1974.
  27. ^ U.S. Government Printing Office (GPO). Washington, DC. Code of Federal Regulations: 21 CFR Part 129, "Processing and Bottling of Bottled Drinking Water."
  28. ^ U.S. GPO, Code of Federal Regulations: 21 CFR § 165.110(a), "Bottled water; Identity."
  29. ^ U.S. GPO, Code of Federal Regulations: 21 CFR § 165.110, "Bottled water."
  30. ^ U.S. GPO, Code of Federal Regulations: 21 CFR § 165.110(a)(2)(i), "Bottled water; Identity; Nomenclature."
Wikimedia Commons has media related to Water as aliment.
Wikimedia Commons has media related to Drinking water.
Look up potable in Wiktionary, the free dictionary.

Template:Dmoz

Retrieved from "https://en.wikipedia.org/w/index.php?title=Drinking_water&oldid=249923935"