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Drinking water quality standards

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Drinking water quality standards describes the quality parameters set for drinking water. 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 as much as 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[1] and in the United States, the United States Environmental Protection Agency (EPA) establishes standards as required by the Safe Drinking Water Act. China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002.[2] For countries without a legislative or administrative framework for such standards, the World Health Organization publishes guidelines on the standards that should be achieved.[3]

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.[4] Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the United States,[5] 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 on non-compliant nations.

Range of standards[edit]

Example of comparison of drinking water quality parameters with thresholds (standards) in Kenya and Ethiopia. The chosen thresholds are from the country's standards or WHO health guideline or East Africa Standard (EAS) for natural potable water.[6]

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, lithium, silver, strontium, and thallium published by the USGS and US EPA were also included in the analysis.[6]

Parametric values[edit]

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 (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 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[edit]

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,[7] and 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.[8] 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 adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002.[2]

European Union[edit]

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.[9]

United States[edit]

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.[10][11]

EPA has set standards for over 90 contaminants organized into six groups: microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals and radionuclides.[12] 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.[13] Many countries look to the standards set by the EPA in the United States for appropriate scientific and public health guidance and may reference or adopt US standards.

World Health Organization Guidelines[edit]

The World Health Organization (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[edit]

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.

" 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.[14]
** 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).[12]
Parameter Table World Health Organization European Union United States China Canada[15] India (BIS)[16]
1,2-dichloroethane " 3.0 μg/L 5 μg/L " "
Acrylamide 0.0005 mg/L 0.10 μg/L TT** " "
Aluminium Al 0.9 mg/L 0,2 mg/L no limit listed 0.03 mg/L
Antimony Sb 0.02 mg/L 5.0 μg/L 6.0 μg/L " 6.00 μg/L
Arsenic As 0.01 mg/L 10 μg/L 10 μg/L 50 μg/L 10.0 μg/L 0.05 mg/L
Barium Ba 1.3 mg/L ns 2 mg/L " 1.00 mg/L
Benzene 0.01 mg/L 1.0 μg/L 5 μg/L " "
Benzo(a)pyrene " 0.010 μg/L 0.2 μg/L 0.0028 μg/L "
Beryllium Be "
Boron B 2.4 mg/L 1.0 mg/L " " 5.00 mg/L 1.0 mg/L
Bromate Br 0.01 mg/L 10 μg/L 10 μg/L " "
Cadmium Cd 0.003 mg/L 5 μg/L 5 μg/L 5 μg/L 5.00 μg/L 0.01 mg/L
Calcium Ca 200 mg/L 75 mg/L
Chromium Cr 0.05 mg/L 50 μg/L 0.1 mg/L 50 μg/L (Cr6) 0.050 mg/L 0.05 mg/L
Cobalt Co "
Copper Cu 2 mg/L 2.0 mg/L 1.3 mg/L* 1 mg/L 1.00 mg/L 0.05 mg/L
Cyanide CN " 50 μg/L 0.2 mg/L 50 μg/L " 0.05 mg/L
Epichlorohydrin " 0.10 μg/L TT** " "
Fluoride F 1.5 mg/L 1.5 mg/L 4 mg/L 1 mg/L " 1.0 mg/L
Gold Au no limit listed
hardness CaCO3 0–75 mg/L = soft 300 mg/L
Iron Fe 0,2 mg/L 0.300 mg/L 0.3 mg/L
Lanthanum La no limit listed
Lead Pb 0.01 mg/L 10 μg/L 15 μg/L* 10 μg/L 10.0 μg/L 0.05 mg/L
Magnesium Mg 50.0 mg/L 30 mg/L
Manganese Mn 0.08 mg/L 0, 05 mg/L 0.050 mg/L 0.1 mg/L
Mercury Hg 0.006 mg/L 1 μg/L 2 μg/L 0.05 μg/L 1.00 μg/L 0.001 mg/L
Molybdenum Mo no limit listed
Nickel Ni 0.07 mg/L 20 μg/L " " no limit listed
Nitrate 50 mg/L 50 mg/L 10 mg/L (as N) 10 mg/L (as N) " 45 mg/L
Nitrite 3 mg/L 0.50 mg/L 1 mg/L (as N) " "
Pesticides (total) " 0.50 μg/L " " " Absent
Pesticides (individual) " 0.10 μg/L " " "
pH 6.5 to 8.5 6.5 to 8.5
Phosphorus P no limit listed
Polycyclic aromatic hydrocarbons " 0.10 μg/L " " "
Potassium K no limit listed
Scandium Sc no limit listed
Selenium Se 0.04 mg/L 10 μg/L 50 μg/L 10 μg/L 10.0 μg/L 0.01 mg/L
Silicon Si no limit listed
Silver Ag 0.1 mg/L 0.050 mg/L
Sodium Na 200 mg/L
Strontium Sr no limit listed
Tetrachloroethene and trichloroethene 40 μg/L 10 μg/L " " "
Tin Sn no limit listed
Titanium Ti no limit listed
Tungsten W no limit listed
Uranium U 0.03 mg/L 0.10 mg/L
Vanadium V no limit listed
Zinc Zn 5.00 mg/L 5.0 mg/L
vinyl chloride 0.50 μg/L
chlorides Cl 250 mg/L 250 mg/L
electrical conductivity 2500 μS/cm at 20 °C
Total dissolved solids <1000 ppm
Sulphate 200 mg/L

See also[edit]


  1. ^ "European Drinking Water Directive". Directorate-General for Environment. Brussels: European Commission.
  2. ^ a b "Environmental quality standards for surface water". Archived from the original on 2018-08-03. Retrieved 2013-02-11.
  3. ^ Guidelines for Drinking-water Quality, Fourth Edition; World Health Organization; 2022
  4. ^ What is the purpose of drinking water quality guidelines/regulations?. Canada: Safe Drinking Water Foundation. Pdf. Archived 2011-10-06 at the Wayback Machine
  5. ^ "Summary of the Safe Drinking Water Act". Washington, D.C.: U.S. Environmental Protection Agency (EPA). 2022-09-12.
  6. ^ a b Nowicki, Saskia; Birhanu, Behailu; Tanui, Florence; Sule, May N.; Charles, Katrina; Olago, Daniel; Kebede, Seifu (2023). "Water chemistry poses health risks as reliance on groundwater increases: A systematic review of hydrogeochemistry research from Ethiopia and Kenya". Science of the Total Environment. 904: 166929. Bibcode:2023ScTEn.904p6929N. doi:10.1016/j.scitotenv.2023.166929. PMID 37689199. Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
  7. ^ "Health (Drinking Water) Amendment Act 2007". drinkingwater.co.nz. Drinking water for New Zealand. 2007. Archived from the original on 2012-07-24. Retrieved 2011-08-09.
  8. ^ "Australian Drinking Water Guidelines (2011)". Canberra: National Health and Medical Research Council, Australian Government.
  9. ^ "Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption, Annex I: Parameters and Parametric Values, Part B: Chemical parameters". EUR-Lex. Luxembourg: European Union. Retrieved 30 December 2019.
  10. ^ "Primacy Enforcement Responsibility for Public Water Systems". Drinking Water Requirements for States and Public Water Systems. EPA. 2022-11-15.
  11. ^ Joseph Cotruvo, Victor Kimm, Arden Calvert. "Drinking Water: A Half Century of Progress." EPA Alumni Association. March 1, 2016.
  12. ^ a b "National Primary Drinking Water Regulations". Ground Water and Drinking Water. EPA. 2023-01-09.
  13. ^ Understanding the Safe Drinking Water Act (Report). EPA. June 2004. EPA 816-F-04-030.
  14. ^ "How EPA Regulates Drinking Water Contaminants". EPA. 2022-11-02.
  15. ^ As per Canadian or B.C. Health Act Safe Drinking Water Regulation BC Reg 230/92, & 390 Sch 120, 2001. Task Force of Canadian Council of Resource & Envir. Ministers Guidelines for Canadian Drinking Water Quality, 1996. Amend. Health Canada (2006).
  16. ^ "Indian Standard Drinking Water Specification" (PDF). Central Ground Water Board. Archived (PDF) from the original on 2016-05-27.

Further reading[edit]