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International Standards

Comparison of Maximum Contaminant Levels in Drinking Water

The following table compares international standard maximum drinking water safe limits for various contaminants by the WHO and various public bodies in the USA and Europe...

If you don't see a contaminant you're looking for please let us know 

Important note: These are maximum levels as judged by regulators etc. It does not necessarily follow that drinking any of these contaminants below this level is safe. As with dietary Recommended Daily Allowances with food many of these limits were set decades ago without much evidence. For example the safe limit for lead is now widely considered to be zero. But as you'll see in the table below the regulators still allow for some lead in drinking water.


Contaminant Details UK Limits WHO California Safe Limit United States Environmental Protection Agency Scandanavia ie Sweden or Denmark or Norway Netherlands / Holland
 Aluminium Aluminum is a metal abundant in the earth's crust that can enter water sources through rock and soil leaching. The concentration of Al3+ existing in groundwater ranges from 0.1 to 8ppm. Aluminum can exist as aluminum hydroxide or sodium aluminate. 200 µg/l 0.1 to 0.2 mg/L 0.2 mg/L 0.05 to 0.2 mg/L  0.2 mg/l  200 µg/l
 Alkalinity Alkalinity is the ability of water to neutralizing acids which is also related to its pH level. Waters with low alkalinity are more corrosive. No standard No standard Non-corrosive Non-corrosive >1.6 mmol/l  n/a
 Ammonium Ammonia is a gaseous compound of hydrogen and nitrogen that is colorless and pungent. It is commonly found in water as a product of the degradation of protein and from industrial waste discharge. Ammonia is used to boost the performance of chlorine in disinfecting water and to reduce carcinogenic chlorination by-products. 0.5 mg/l No guideline No direct standard No standard 0.50 mg/l  0.50 mg/l
Arsenic Hitler's choice of poison. Occurs naturally in low levels from water passing through rock. 0.01 mg/l 0.01 mg/l zero  zero 0.01 mg/l  0.01 mg/l
Asbestos Another great science-meets-money success story. Asbestos was widely used as a fire-resistant and versatile material until it was realised that inhaling asbestos dust is extremely harmful. (Sadly it's reportedly still in use in some Indian and Chinese manufacturing No Guideline   No guideline  7 MFL  7 MFL No guideline  No guideline
Boron Boron in natural water exists in small amounts as boric acid with borate ions. Boron is absorbed by soils and sediments depending on the concentration and pH level of the water.  1 mg/l 0.3 mg/l 1 mg/l 1 mg/l 1.0 mg/l 1.0 mg/l
Cadmium   0.005 mg/l 0.003 mg/l 0.005 mg/l 0.005 mg/l 0.005 mg/l 0.005 mg/l
Calcium Calcium is an important element for human's health. One to two grams of calcium is required daily for human consumption. Most of the calcium in the body are found in bones and teeth. It is also one of the components of water hardness. n/a n/a n/a n/a n/a  n/a
Calcium hardness Calcium hardness is the measurement of calcium alone expressed in mg/l CaCO3 n/a 100 mg/l  See guide n/a n/a n/a  n/a
Chlorine   No guideline No guideline 4 mg/l 4 mg/l No guideline No guideline
Chloride Chloride exists naturally in water with the highest concentration found in sea water. It is also one of the components of salt thus water with high levels of chloride are found to taste salty. 250 mg/l 250 mg/l 500 mg/L 250 mg/l 250 mg/l  250 mg/l
Chromium Chromium may exist naturally in water depending on the mineral deposits in water sources. High level of chromium is considered toxic thus there is very limited amount in drinking water. 0.05 mg/l 0.05 mg/l 0.05 mg/l 0.1 mg/L 0.05 mg/l  0.05 mg/l
Copper Copper is an essential element in human diet. 2 mg of copper is the prescribed daily intake and should not exceed 10 mg and 12 mg for females and males respectively. Copper deficiency may lead to bone disease and cardiovascular diseases. Copper in water can source from industrial waste and copper salts used to control algae in reservoirs. 2.0 mg/l 2.0 mg/l 1.3 mg/L 1.3 mg/L 2.0 mg/l  2.0 mg/l
Cyanide Cyanide is a highly toxic contaminant if found in high concentrations. It is commonly found in industrial waste from the manufacturing of metals and electronics. It may occur in water naturally depending on the mineral deposits in the water source.  0.05 mg/l 0.07 mg/l 0.15 mg/L 0.2 mg/L 0.05 mg/l  0.05 mg/l
Electrical conductivity It is the ability of water to conduct electricity or electric current also referred to as specific conductance. It measures the amount of mineral salts in water. Although there is no direct health and sanitary signifance, conductivity aids in determining the range of hardness and alkalinity of water. 2500 µS/cm at 20°C 250 microS/cm 1600 umhos 2500 μS/cm at 20°C 2500 μS/cm at 20°C  2500 μS/cm at 20°C
Fluoride Fluoride is a binary compound of fluorine and another element. 0.6 mg/l to 1 mg/l of Fluoride in water decreases  tooth decay (Public health officials like it becuase it helps deprived children who don't brush their teeth). However, Fluoride content of more than 1.5 mg/l leads to teeth mottling. Adding fluoride to water supplies is controversial. Fluoride may exist naturally in water in different concentrations. 1.5 mg/l 1.5 mg/l 2 mg/L 4 mg/L 1.5 mg/l  1.5 mg/l
Hardness, total (as CaCO3) Total hardness is the measurement of both calcium and magnesium expressed as mg/l CaCO3. General EPA rating is Soft up to 50 mg/l CaCO3
Moderately Soft 51-100 mg/l CaCO3
Slightly Hard 101 - 150 mg/l CaCO3
Moderately Hard 151-250 mg/l CaCO3
Hard 251-350 mg/l CaCO3
Excessively Hard over 350 mg/l CaCO3
No guideline No guideline No guideline No guideline No guideline  No guideline
Iron, total and free Insoluble forms of iron are found in rocks and soils. Iron in water may occur when water passes through ground formations with reactions that result in soluble forms of iron. The main problems of water with excessive iron content are in color and turbidity.  0.2 mg/l No guideline 0.3 mg/L 0.3 mg/L 0.2 mg/l  0.2 mg/l
Lead Lead is a heavy metal that can accummulate in body and is thus controlled in drinking water. In older houses with lead pipework installed, there is danger of lead entering the water supply.  0.01 mg/l 0.01 mg/l 0.015 mg/L 0.015 mg/L 0.01 mg/l 0.01 mg/l
Manganese Manganese is similar to iron since both are found in soil and ground water. It is usually removed during water treatment. There is a stricter limit for manganese because the discoloration problem that occurs is worse than that of iron.  0.5 mg/l 0.5 mg/l 0.5 mg/l 0.5 mg/l 0.5 mg/l  0.5 mg/l
Magnesium hardness Magnesium hardness is the difference between total hardness and calcium hardness n/a 50 mg/l - 100 mg/l n/a n/a n/a  n/a
Mercury Mercury is known to cause kidney damage. It is widely used in manufacturing processes and usually enters drinking water supplies through industrial discharges. 0.001 mg/l 0.001 mg/l 0.002 mg/l 0.002 mg/l 0.001 mg/l 0.001 mg/l
Nickel

Nickel is a very common metal found in  soil - and therefore food - at widely varying levels. It is a major component/hazard of cigarette smoke. Too much Nickel in the body is thought to result in cancers and birth defects.

0.02 mg/l 0.02 mg/l No guideline No guideline 0.02 mg/l  0.02 mg/l
Nitrate Nitrates can end up in drinking water from nitrogen fertilizers. Excess nitrates can cause can cause methemoglobinemia, or "blue baby" disease. It can also be an indicator of serious contaminants like bacteria or pesticides. 0.50 mg/l 3 mg/l 1 mg/L 1 mg/L 0.50 mg/l  0.50 mg/l
pH pH is a measure of acidity of water reflected by the number of hydrogen ions. An equal number of H+ and OH- ions in water means that the water is neutral. pH has a range of 0 to 14 with 7 being neutral. A pH below 7 indicates a substance is acidic while a pH above 7 indicates a substance is basic. 6.5 (min) - 9.5 No guideline 6.5 - 8.5. 6.5 - 8.5. 6.5 - 9.5  6.5 - 9.5
Potassium Potassium is an important component of artificial fertilizers and is also found naturally in soil. The concentration of potassium in drinking water are at levels that do not pose health risks. No standard No standard No standard No standard No standard  No standard
Sodium Sodium is an abundant element and occurs naturally in waters and is normally consumed through salt. Consumption is limited to 5 grams daily and excessive amounts may result in hypertension and damaged kidneys.  200 mg/l 200 mg/l 100 mg/L 30-60 mg/L 200 mg/l  200 mg/l
Sulphate Sulphates occur naturally in water in varying concentrations depending on the terrain water flow through. Sulfates are commonly from the result of sulfite ore oxidation and industrial wastes. The combination of sulphate with sodium and magnesium creates a laxative effect. The concentration of sulphate in drinking water have no health risks. 250 mg/l 500 mg/l 500 mg/l 250 mg/l 250 mg/l  250 mg/l
Sulphide Anaerboic decomposition of organic matter produces sulphides. Iron sulphides are found in sedimentary rocks and turn to sulphate when oxidised. Sulphide is toxic to humans and aquatic life and causes odor problems in water when the balance between the dissociated and undissociated forms is disrupted. 250 mg/l 250 mg/l 250 mg/l 250 mg/l 250 mg/l  250 mg/l
Total dissolved solids A measurement of the total amount of solids existing in water after it is filtered. Also referred to as Total Filtrable Solids, it consists of both ionised and non-ionised matter. Conductivity is often used to estimate the amount of total dissolved solids. No guidance 1000 mg/litre 1000 mg/litre 500 mg/L No guidance  No guidance
 Turbidity Turbidity is caused by fine particles in water that cannot be filtered that gives the appearance of cloudiness. Health risks relating to turbidity are determined by the type of matter causing turbidity. There can be serious effects when the particles causing turbidity interfere with treatment and disinfection processe. 4 NTU 5 NTU/JTU 5 NTU/JTU 5 NTU/JTU No Guidance  1 NTU 
 Zinc Zinc is an important element for humans but should not ba taken in high doses. Problems related with zinc refer mostly to taste but in aquatic life it's toxicity depends on the hardness of water. An increased hardness of water means decreased toxicity of zinc. No Standard 3 mg/l 5.0 mg/L 5.0 mg/L 100 µg/l  No Standard

 

 

Sources: 

https://www.who.int/water_sanitation_health/water-quality/en/

https://www.epa.gov/sites/production/files/2018-03/documents/dwtable2018.pdf

https://www.anglianwater.co.uk/_assets/media/Standards_Current.pdf

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:31998L0083&from=EN

Further Reading

https://www.rivm.nl/bibliotheek/rapporten/2017-0050.pdf

https://www.fhi.no/en/op/hin/smitte/drinking-water-in-Norway/#international-differences

 

 

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