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Drinking water is water that is intended to be ingested through drinking by humans. Water of sufficient quality to serve as drinking water is termed potable water whether it is used as such or not. Although many sources are utilized by humans, some contain disease vectors or pathogens and cause long-term health problems if they do not meet certain water quality guidelines. Water that is not harmful for human beings is sometimes called safe water, water which is not contaminated to the extent of being unhealthy. The available supply of drinking water is an important criterion of carrying capacity, the population level that can be supported by planet Earth.

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, primarily arising from industrial contamination and pollution. As of the year 2000, 27 percent of the populations of lesser developed countries did not have access to safe drinking water^[1]. 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 Travelers.

Typically water supply networks deliver a single quality of water, whether it is to be used for drinking, washing or landscape irrigation; one counterexample is urban China, where drinking water can be optionally delivered by a separate tap. In the United States, public drinking water is governed by the Safe Drinking Water Act (SDWA). Among other provisions, it protects the right of employees to report potential violations. ^[2] Within 30 days of any retaliation, a whistleblower can file a complaint with the Occupational Safety and Health Administration (OSHA).

Contents 1 Metabolism 2 Requirement 3 Access to drinking water 4 Drinking water quality monitoring 5 See also 6 References 7 External links

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, sweating and urination. 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 very small amounts 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.

RDI for water is 3.7 L/day for males aged 19-30 years. Food contributes with 0,5–1 L and the metabolism of protein, fat and carbohydrates generates another 2,5–4 dL^[3]. Thus, a person needs to drink another 2-3 L/day of water.

Earth's surface consists of 70% water. Water is available almost everywhere if proper methods are used to get it. As a country’s economy becomes stronger (as its GNP per capita or PPP rise) 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.

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 access to safe drinking water to the populations in several countries is listed below.^[4]

Table 2: Percentage of population with access to safe drinking water

Country	%		Country	%		Country	%		Country	%
Albania	97		Algeria	89		Azerbaijan	78		Brazil	87
Chile	93		Cuba	91		Egypt	97		Iraq	85
Iran	92		Mexico	88		Morocco	80		Peru	80
Syria	80		Sudan	67		South Africa	86		Turkey	82
Tunisia	80		Venezuela	83		Zimbabwe	83

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.

Common places to find safe drinking water after a disaster are

• Water heater
• Household water pipes

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 seven hundred 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 some six hundred and twenty seven million people without access to safe drinking water. [1]

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 life. 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. [2] 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.[3]

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Parameters for drinking water quality typically fall under two categories: chemical/physical and bacteriological. Chemical/physical parameters include heavy metals, total suspended solids (TSS), and turbidity. Bacteriological parameters include total coliform and fecal coliform.

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 of the drinking water and may complicate the treatment of bacteria, viruses, and pathogens.

The original name for bacterial contamination is a laboratory analysis of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like Escherichia coli) serves as an indication of contamination by sewage. Bacteriological parameters are typically of greatest concern because of their immediate health risk.

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• Backflow prevention device
• Bacterial water analysis
• Boil water advisory
• Bottled water
• Carl Rogers Darnall
• Drinking water quality legislation of the United States
• Food safety
• Giardia lamblia
• Overpopulation
• Plumbing
• Tap water
• Waterborne diseases
• Water crisis
• Water fluoridation
• Water purification
• Water resources
• Water law

This article or section includes a list of references or external links, but its sources remain unclear because it lacks in-text citations. You can improve this article by introducing more precise citations.

• International Action - A Non-profit committed to providing access to clean water to the people of Haiti, using inexpensive technology
• Tap vs. Bottle - Santa Clara Valley Water District
• California Dept. of Public Health - The drinking water regulator for the State of California.
• Drinking Water Inspectorate - The drinking water regulator in England and Wales.
• KnowH2O - A water education initiative from PlayPumps International about drinking water and global water issues.
• Louisiana Homeland Security Emergency Preparedness - Locating Safe Drinking Water
• OpenWater Project - Instructional content about safe drinking water.
• Safe Drinking Water Is Essential - An online exhibit of the Marian Koshland Science Museum of the National Academy of Sciences that examines the state of the world's water supply and what can be done to improve it.
• Safe Water for International Travelers - A broad classification of drinking water safety worldwide.
• Safe Water International - Non-Profit committed to creating solutions to unsafe drinking water problems
• UKWIR Forefront - UK Water Industry Research Reports concerning Drinking Water Quality & Health
• US Environmental Protection Agency - Drinking water program