Water Quality
Standards
Copper and its compounds are used in electrical wiring, water pipes, cooking utensils, and electroplating, and as algicides and food additives. Copper concentrations in drinking-water vary widely as a result of variations in pH, hardness, and copper availability in the distribution system. Levels of copper in running water tend to be low, whereas those of standing or partially flushed water samples are more variable and can be substantially higher, particularly in areas where the water is soft and corrosive. Adult intake of copper from food is usually 1–2 mg/day and may be considerably increased by consumption of standing or partially flushed water from a system that contains copper pipes or fittings.
Copper is an essential nutrient, required for the proper functioning of many important enzyme systems. In mammals, absorption of copper occurs in the upper gastrointestinal tract and is controlled by a complex homeostatic process. Absorption is influenced by the presence of competing metals, dietary proteins, fructose, and ascorbic acid. The major excretory pathway for absorbed copper is bile. In humans, the highest concentrations of copper are found in the liver, brain, heart, kidney, and adrenal glands. The liver of newborn infants contains about 10 times as much copper as the adult liver and accounts for 50–60% of the total body copper.
Copper utilization is affected by a number of genetic disorders. The genetic abnormalities associated with Menke syndrome, Wilson disease, and aceruloplasminaemia are fairly well understood, and there is some evidence to suggest a genetic basis for Indian childhood cirrhosis and idiopathic copper toxicosis.
Acute gastrointestinal effects may result from exposure to copper in drinking-water, although the levels at which such effects occur are not defined with any precision. Long-term intake of copper in the diet in the range 1.5–3 mg/day has no apparent adverse effects. Daily intake of copper below this range can lead to anaemia, neutropenia, and bone demineralization in malnourished children. Adults are more resistant than children to the symptoms of copper deficiency.
The IPCS Task Group responsible for preparation of the Environmental Health Criteria monograph for copper concluded that:
"The upper limit of the AROI [acceptable range of oral intake] in adults is uncertain but it is most likely in the range of several but not many mg per day . . . (several meaning more than 2 or 3 mg/day). This evaluation is based solely on studies of gastrointestinal effects of copper-contaminated drinking-water. A more specific value for the upper AROI could not be confirmed for any segment of the general population . . . The available data on toxicity in animals were considered unhelpful in establishing the upper limit of the AROI, due to uncertainty about an appropriate model for humans."
A copper level of 2 mg/litre in drinking-water should not cause any adverse effects and provides an adequate margin of safety. The epidemiological and clinical studies conducted to date are too limited to allow a clear effect level to be established with any accuracy. Thus, it is recommended that this guideline value for copper of 2 mg/litre remain provisional as a result of uncertainties in the dose–response relationship between copper in drinking-water and acute gastrointestinal effects in humans. It is also noteworthy that copper is an essential element.
It is stressed that the outcome of epidemiological studies in process in Chile, Sweden, and the USA may permit more accurate quantification of effect levels for copper-induced toxicity in humans, including sensitive subpopulations.
Staining of laundry and sanitary ware occurs at copper concentrations above 1 mg/litre. At levels above 5 mg/litre, copper also imparts a colour and an undesirable bitter taste to water.
