Drinking water, also known as potable water or improved drinking water, is water safe enough for drinking and food preparation. Globally, in 2012, 89% of people had access to water suitable for drinking.〔(【引用サイトリンク】url=http://www.who.int/mediacentre/factsheets/fs391/en/ )〕 Nearly 4 billion had access to tap water while another 2.3 billion had access to wells or public taps.〔 1.8 billion people still use an unsafe drinking water source which may be contaminated by feces.〔 This can result in infectious diarrhea such as cholera and typhoid among others.〔
Water is essential for life. The amount of drinking water required is variable.〔 It depends on physical activity, age, health issues, and environmental conditions.〔 It is estimated that the average American drinks about one liter of water a day with 95% drinking less than three liters per day. For those working in a hot climate, up to 16 liters a day may be required.〔 Water makes up about 60% of weight in men and 55% of weight in women. Infants are about 70% to 80% water while the elderly are around 45%.
Typically in developed countries, tap water meets drinking water quality standards, even though only a small proportion is actually consumed or used in food preparation. Other typical uses include washing, toilets, and irrigation. Greywater may also be used for toilets or irrigation. Its use for irrigation however may be associated with risks.〔 Water may also be unacceptable due to levels of toxins or suspended solids. Reduction of waterborne diseases and development of safe water resources is a major public health goal in developing countries. Bottled water is sold for public consumption in most parts of the world. The word ''potable'' came into English from the Late Latin ''potabilis'', meaning drinkable.
(詳細はfl oz each (240 mL) are required by an adult per day (64 fl oz, or 1.89 litres).〔U.S. Environmental Protection Agency (EPA). Dallas, TX (2000-05).(【引用サイトリンク】title=Chapter 3: Exposure Scenario Selection ) RCRA Delisting Technical Support Document. p. 8.〕 The British Dietetic Association recommends 1.8 litres. However, various reviews of the evidence performed in 2002 and 2008 could not find any solid scientific evidence recommending eight glasses of water per day.〔(Research debunks health value of guzzling water ). Reuters, April 2008.〕〔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.〕 In the United States, the reference daily intake (RDI) for total water intake is 3.7 litres per day (L/day) for human males older than 18, and 2.7 L/day for human females older than 18 which includes drinking water, water in beverages, and water contained in food.〔(【引用サイトリンク】title=US daily reference intake values )〕 An individual's thirst provides a better guide for how much water they require rather than a specific, fixed quantity.〔
The drinking water contribution to mineral nutrients intake is also unclear. 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 minerals. Examples include calcium, zinc, manganese, phosphate, fluoride and sodium compounds.〔(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.〕 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 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.
Fluid balance is key. 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.
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