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Drinking water quality standards describes the quality parameters set for drinking water . Despite the truism that every human on this planet needs drinking water to survive and that water can contain many harmful constituents, there are no universally recognised and accepted international standards for drinking water. Even where standards do exist, and are applied, the permitted concentration of individual constituents may vary by as much as ten times from one set of standards to another.
Many developed countries specify standards to be applied in their own country. In Europe this includes the Drinking water directive and in the USA the United States Environmental Protection Agency (EPA) establishes down standards as required by the Safe Drinking Water Act. For countries without a legislative or administrative framework for such standards, the World Health Organisation publishes guidelines on the standards that should be achieved.
Where standards do exist most are expressed as guidelines or targets and very few have any legal basis or are subject to enforcement. The European Drinking Water Directive and the Safe Water Act in the USA are two exceptions where there is a requirement to legally comply 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 on non-compliant nations.
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
Range of standards
Although drinking water standards are frequently referred to as if they are simple lists of parametric values, standards documents also specify sampling location choice, sampling methods, laboratory analytical methods and laboratory AQC. In addition a number of standards documents also make reference to the statistical treatment of results, dealing with temporal and seasonal variations, summation of related parameters and treatment of apparently aberrant results.
- (Parametric value also has a specific and different mathematical meaning)
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 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, pH and the organoleptic parameters (taste and smell).
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 may be measured as Nitrite ion or expressed as N. A standard of Nitrite as N of 1.4 mg/l would be equal to a nitrite ion concentration of 4.6 mg/l - an apparent difference of nearly three fold.
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 systems.
European Union standards
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 5.0 μg/l
- Arsenic 10 μg/l
- Benzene 1.0 μg/l
- Benzo(a)pyrene 0.010 μg/l
- Boron 1.0 mg/l
- Bromate 10 μg/l
- Cadmium 5.0 μg/l
- Chromium 50 μg/l
- Copper 2.0 mg/l
- Cyanide 50 μg/l
- 1,2-dichloroethane 3.0 μg/l
- Epichlorohydrin 0.10 μg/l
- Fluoride 1.5 mg/l
- Lead 10 μg/l
- Mercury 1.0 μg/l
- Nickel 20 μg/l
- Nitrate 50 mg/l
- Nitrite 0.50 mg/l
- Pesticides 0.10 μg/l
- Pesticides - Total 0.50 μg/l
- Polycyclic aromatic hydrocarbons 0.10 μg/l Sum of concentrations of specified compounds;
- Selenium 10 μg/l
- Tetrachloroethene and Trichloroethene 10 μg/l Sum of concentrations of specified parameters
- Trihalomethanes — Total 100 μg/l Sum of concentrations of specified compounds
- Vinyl chloride 0.50 μg/l
United States standards
In the USA the legislation controlling drinking water quality is the Safe Water Act which is implemented federally by the EPA. However many individual States also apply their own standards which may be more rigorous or include additional parameters. Standards set by the EPA in the USA are not international standards since they apply to a single country. However many countries look to the USA for appropriate scientific and public health guidance and may adopt USA standards.
World Health Organisation guidelinesThese guidelines include the following recommended limits on naturally occurring constituents that may have direct adverse health impact:
- Arsenic 10μg/l
- Barium 700μg/l
- Boron 2400μg/l
- Chromium 50μg/l
- Fluoride 1500μg/l
- Selenium 40μg/l
- Uranium 30μg/l
- Cadmium 3μg/l
- Mercury 6μg/l For inorganic mercury
- Benzene 10μg/l
- Carbon tetrachloride 4μg/l
- 1,2-Dichlorobenzene 1000μg/l
- 1,4-Dichlorobenzene 300μg/l
- 1,2-Dichloroethane 30μg/l
- 1,2-Dichloroethene 50μg/l
- Dichloromethane 20μg/l
- Di(2-ethylhexyl)phthalate 8 μg/l
- 1,4-Dioxane 50μg/l
- Edetic acid 600μg/l
- Ethylbenzene 300 μg/l
- Hexachlorobutadiene 0.6 μg/l
- Nitrilotriacetic acid 200μg/l
- Pentachlorophenol 9μg/l
- Styrene 20μg/l
- Tetrachloroethene 40μg/l
- Toluene 700μg/l
- Trichloroethene 20μg/l
- Xylenes 500μg/l
Comparison of parametric values
The following table provides a comparison of a selection of parameters concentrations listed by WHO, the European Union and the EPA.
" indicates that no standard has been identified by editors of this article and ns indicates that no standard exists.
|Parameter||World Health Organization||European Union||United States|
|Fluoride||1.5 mg/l||1.5 mg/l||4 mg/l|
|Lead||“||10 μg/l||15 μg/l|
|Pesticides (individual)||“||0.10 μg/ l||“|
|Pesticides — Total||“||0.50 μg/l||“|
|Polycyclic aromatic hydrocarbons l||“||0.10 μg/||“|
|Tetrachloroethene and Trichloroethene||40μg/l||10 μg/l||“|