Copper
(endorsed 2001)
Guideline
Based on health considerations, the concentration of copper in drinking water should not exceed 2 mg/L.
Based on aesthetic considerations, the concentration of copper in drinking water should not exceed 1 mg/L.
General description
Copper is widely distributed in rocks and soils as carbonate and sulfide minerals.
Copper is relatively resistant to corrosion and is used in domestic water supply pipes and fittings. It is also used in the electroplating and chemical industries, and in many household goods. Copper sulfate is used extensively to control the growth of algae in water storages.
Copper is present in uncontaminated surface waters at very low concentrations, usually less than 0.01 mg/L. The concentration can rise substantially when water with a low pH and hardness remains in stagnant contact with copper pipes and fittings. Under these conditions, the concentration of copper can reach 5 mg/L or higher. In one extreme case overseas, a concentration of 22 mg/L was reported.
The taste threshold for copper is in the range 1–5 mg/L, depending on the water purity. Concentrations above 1 mg/L may cause blue or green stains on sanitary ware. Such stains may also be due to slowly leaking taps, where copper corrosion occurs over a long time, and are not necessarily due to high concentrations of copper in drinking water.
Food is the main source of copper intake. Intake from water would normally be less than 10% of total intake.
Typical values in Australian drinking water
In major Australian reticulated supplies, total copper concentrations range up to 0.8 mg/L, with typical concentrations of about 0.05 mg/L.
Treatment of drinking water
Copper can be removed from drinking water by increasing the pH, and then using the water treatment processes of coagulation followed by filtration. Aggressive water, which is likely to induce corrosion of copper pipes, should be stabilised with respect to pH and hardness as part of the treatment process prior to distribution in order to minimise copper leaching.
Measurement
The copper concentration can be determined by inductively coupled plasma emission spectroscopy (APHA Method 3500-Cu Part C 1992) with an estimated limit of determination of 0.01 mg/L. Alternatively, flame or graphite furnace atomic absorption spectroscopy can be used (APHA 3500-Cu Part B 1992) with limits of determination of 0.05 mg/L and 0.005 mg/L respectively.
Health considerations
Copper is an essential trace element for humans. It is estimated that adult requirements are about 2–3 mg per person per day. High doses of copper (above 50 mg/kg bodyweight) can be lethal.
The absorption of copper by the gastrointestinal tract is in the range of 25–60%, depending on a number of factors, including copper speciation and copper dietary status (Olivares et al. 1998). Copper is stored in the liver, brain and muscle tissue. High concentrations can also be found in the kidneys, heart and hair. Copper is eliminated from the body mainly in the bile.
Many cases of copper poisoning have been reported, including cases involving the poisoning of children who had their food prepared in copper or brass pots (Tanner 1998). Copper poisoning has resulted in cirrhosis of the liver and, in extreme cases, death. Other less severe symptoms associated with the consumption of water containing 3–5 mg/L copper (but not 1 mg/L) are gastrointestinal symptoms such as nausea, abdominal pain and vomiting (Pizarro et al. 1999). Infants are thought to be most susceptible, though in one study of 3-month-old infants given water containing 2 mg/L copper over 9 months there were no acute or chronic adverse consequences (Olivares et al. 1998). In the genetic disorders Wilson’s disease and idiopathic copper toxicosis, sufferers are particularly susceptible to copper (Lönnerdal and Uauy 1998).
Apart from humans, sheep are the most susceptible animals to the toxic effects of copper, with a daily intake of 1–2 mg/kg body weight resulting in serious illness and death.
Copper was not found to be carcinogenic in tests with mice and dogs. The results of mutagenicity tests with different strains of bacteria were generally negative. Tests for mutagenicity using mammalian cells, both in vitro and in vivo, gave predominantly positive results.
Derivation of guideline
The health-based guideline value of 2 mg/L (rounded up) for copper in drinking water was derived as follows:
where:
0.5 mg/kg body weight per day is the provisional maximum tolerable daily intake for humans (WHO 1982).
70 kg is the average weight of an adult.
0.1 is the proportion of total daily intake attributable to the consumption of water.
2 L/day is the average amount of water consumed by an adult.
In this derivation, which others have also used and which is still endorsed by the World Health Organization (2006), there is considerable uncertainty (Fitzgerald 1998). Nevertheless, on the basis of recent copper investigation studies, the derived guideline value appears to be a safe level for infants and is just below a level where minor symptoms were observed in adults.
In premises with a history of copper corrosion, water that has been in stagnant contact (6 hours or more) with copper pipes and fittings should not be used in the preparation of food or drink. Copper levels can be effectively reduced by flushing the taps for 1 minute.
References
APHA Method 3500-Cu Part B (1992). Copper: Atomic Absorption Spectrometric method. Standard Methods for the Examination of Water and Wastewater, 18th edition. American Public Health Association, Washington.
APHA Method 3500-Cu Part C (1992). Copper: Inductively Coupled Plasma method. Standard Methods for the Examination of Water and Wastewater, 18th edition. American Public Health Association, Washington.
Fitzgerald DJ (1998). Safety guidelines for copper in water. American Journal of Clinical Nutrition, 67(suppl):1098S–1102S.
Lönnerdal B, Uauy R (1998). Genetic and environmental determinants of copper metabolism. American Journal of Clinical Nutrition, 67(5S).
Olivares M, Pizarro F, Speisky H, Lönnerdal B, Uauy R (1998). Copper in infant nutrition: Safety of World Health Organization provisional guideline value for copper content of drinking water. Journal of Pediatric Gastroenterology and Nutrition, 26:251–257.
Pizarro F, Olivares M, Uauy R, Contreras P, Rebelo A, Gidi V (1999). Acute gastrointestinal effects of graded levels of copper in drinking water. Environmental Health Perspectives, 107:117–121.
Tanner MS (1998). Role of copper in Indian childhood cirrhosis. American Journal of Clinical Nutrition, 67(suppl):1074S–1081S.
WHO (World Health Organization) (1982). Toxicological evaluation of certain food additives: copper. WHO, Joint Food and Agriculture Organization of the United Nations/WHO Expert Committee on Food Additives, 17, 265–296, Geneva, Switzerland.
WHO (World Health Organization) (2006). Guidelines for Drinking-water Quality. 3rd Edition, WHO, Geneva, Switzerland.
Last updated
