Drinking water quality standards describes the quality parameters set for

drinking water Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often (but not always) supplied through taps, in which case it is also calle ...

. Water may contain many harmful constituents, yet there are no universally recognized 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 the European Drinking Water Directive and in the United States, the

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...

(EPA) establishes standards as required by the

Safe Drinking Water Act The Safe Drinking Water Act (SDWA) is the primary federal law in the United States intended to ensure safe drinking water for the public. Pursuant to the act, the Environmental Protection Agency (EPA) is required to set standards for drinking wa ...

. China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002. For countries without a legislative or administrative framework for such standards, the

World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...

publishes guidelines on the standards that should be achieved. 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. Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the United States, 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 the

European Commission The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...

on non-compliant nations.

Range of standards

Drinking water standards include lists of parametric values, and also specify the sampling location, sampling methods, sampling frequency, analytical methods, and laboratory accreditation ( AQC). In addition, a number of standards documents also require calculation to determine whether a level exceeds the standard, such as taking an average. Some standards give complex, detailed requirements for the statistical treatment of results, temporal and seasonal variations, summation of related parameters, and mathematical treatment of apparently aberrant results. For example, when comparing drinking water quality parameters in Kenya and Ethiopia with published guideline values (thresholds), scientists compared several standards: the Kenyan drinking water standard, Ethiopian standard, WHO health guideline, WHO Aesthetic guideline and the EAS (East African Standards) for natural potable water. Furthermore, the non-regulatory health-based screening levels (HBSLs) for

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...

, and

thallium Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...

published by the

USGS The United States Geological Survey (USGS), founded as the Geological Survey, is an government agency, agency of the United States Department of the Interior, U.S. Department of the Interior whose work spans the disciplines of biology, geograp ...

and US EPA were also included in the analysis.

Parametric values

A parametric value in this context is most commonly the concentration of a substance, e.g. 30 mg/L of iron. It may also be a count such as 500 '' E. coli'' per litre or a

statistical Statistics (from German language, German: ', "description of a State (polity), state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a s ...

value such as the average concentration of copper is 2 mg/L. Many countries not only specify parametric values that may have health impacts but also specify parametric values for a range of constituents that by themselves are unlikely to have any impact on health. These include colour,

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wa ...

, pH, and the

organoleptic Organoleptic properties are the aspects of food, water or other substances as apprehended via the senses—including taste, sight, smell, and touch. In traditional U.S. Department of Agriculture meat and poultry inspections, inspectors p ...

(aesthetic) parameters (taste and odour). It is possible and technically acceptable to refer to the same parameter in different ways that may appear to suggest a variation in the standard required. For example,

nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

may be measured as nitrite ion or expressed as N. A standard of "nitrite as N" set at 1.4 mg/L equals a nitrite ion concentration of 4.6 mg/L. This is an apparent difference of nearly threefold.

Standards by country

Countries with guideline values as their standards include Canada, which has guideline values for a relatively small suite of parameters, New Zealand, where there is a legislative basis, but water providers have to make "best endeavours" to comply with the standards, and Australia.

Australia

Drinking water quality standards in Australia have been developed by the Australian Government National Health and Medical Research Council (NHMRC) in the form of the Australian Drinking Water Guidelines. These guidelines provide contaminant limits (pathogen, aesthetic, organic, inorganic,and radiological) as well as guidance on applying limits for the management of drinking water in Australian drinking water treatment and distribution.

China

China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002.

European Union

The following parametric standards are included in the Drinking Water Directive and are expected to be enforced by appropriate legislation in every country in the European Union. Simple parametric values are reproduced here, but in many cases the original directive also provides caveats and notes about many of the values given. * Acrylamide 0.10 μg/L *

Antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...

5.0 μg/L *

Arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

10 μg/L *

Benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

1.0 μg/L * Benzo(a)pyrene 0.010 μg/L *

Boron Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...

1.0 mg/L * Bromate 10 μg/L *

Cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

5.0 μg/L *

Chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

50 μg/L *

Copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

2.0 mg/L *

Cyanide In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. Ionic cyanides contain the cyanide anion . This a ...

50 μg/L *

1,2-dichloroethane The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon. It is a colourless liquid with a chloroform-like odour. The most common use of 1,2-dichloroethane is in the production of vinyl ...

3.0 μg/L * Epichlorohydrin 0.10 μg/L *

Fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an Inorganic chemistry, inorganic, Monatomic ion, monatomic Ion#Anions and cations, anion of fluorine, with the chemical formula (also written ), whose ...

1.5 mg/L *

Lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

10 μg/L * Mercury 1.0 μg/L *

Nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

20 μg/L *

Nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...

50 mg/L *

Nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

0.50 mg/L *

Pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

s 0.10 μg/L *Pesticides 0.50 μg/L total * Polycyclic aromatic hydrocarbons 0.10 μg/L sum of concentrations of specified compounds *

Selenium Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...

10 μg/L *

Tetrachloroethene Tetrachloroethylene, also known as perchloroethylene or under the systematic name tetrachloroethene, and abbreviations such as perc (or PERC), and PCE, is a chlorocarbon with the formula . It is a non-flammable, stable, colorless and heavy liqu ...

and trichloroethene 10 μg/L sum of concentrations of specified parameters * Trihalomethanes 100 μg/L sum of concentrations of specified compounds *

Vinyl chloride Vinyl chloride is an organochloride with the formula H2C =CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. It is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC). Vinyl chloride is a ...

0.50 μg/L

United States

In the United States, the federal legislation controlling drinking water quality is the Safe Drinking Water Act (SDWA) which is implemented by EPA, mainly through state or territorial health agencies. EPA has set standards for over 90 contaminants organized into six groups: microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals and radionuclides. States and territories must implement rules that are at least as stringent as EPA's to retain primary enforcement authority (primacy) over drinking water. Many states also apply their own state-specific standards, which may be more rigorous or include additional parameters. Many countries look to the standards set by the EPA in the United States for appropriate scientific and

public health Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the de ...

guidance and may reference or adopt US standards.

World Health Organization Guidelines

The

(WHO) Guideline for Drinking-water Quality (GDWQ) include the following recommended limits on naturally occurring constituents that may have direct adverse health impact: *Arsenic 10 μg/L *Barium 10 μg/L *Boron 2400 μg/L *Chromium 50 μg/L *Fluoride 1500 μg/L *Selenium 40 μg/L *Uranium 30 μg/L Organic species: *Benzene 10 μg/L *Carbon tetrachloride 4 μg/L *1,2-Dichlorobenzene 1000 μg/L *1,4-Dichlorobenzene 300 μg/L *1,1-Dichloroethane 30 μg/L *1,2-Dichloroethene 50 μg/L *Dichloromethane 20 μg/L *Di(2-ethylhexyl)phthalate 8 μg/L *1,4-Dioxane 50 μg/L *Edetic acid 600 μg/L *Ethylbenzene 300 μg/L *Hexachlorobutadiene 0.6 μg/L *Nitrilotriacetic acid 200 μg/L *Pentachlorophenol 9 μg/L *Styrene 20 μg/L *Tetrachloroethene 40 μg/L *Toluene 700 μg/L *Trichloroethene 20 μg/L *Xylene 500 μg/L

Comparison of parametric values

The following table provides a comparison of a selection of parameters for concentrations listed by WHO, the European Union, EPA, and Ministry of Environmental Protection of China. ; Notes : " indicates that no standard has been identified by editors of this article and ns indicates that no standard exists. μg/L = micrograms per litre, or 0.001 ppm; mg/L = 1 ppm, or 1000 μg/L. : * means action level; not a concentration standard. A public water system exceeding the action level must implement "treatment techniques" which are enforceable procedures. : ** TT (treatment technique). The public water system must certify that the combination of dose and monomer level does not exceed: acrylamide = 0.05% dosed at 1 mg/L (or equivalent); epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent).