Copper (Cu) is malleable and ductile, conducts heat and electricity exceedingly well and is very little altered in its functional capacity by exposure to dry air. In a moist atmosphere containing carbon dioxide it becomes coated with a green carbonate. Copper is an essential element in human metabolism.
Occurrence and Uses
Copper occurs principally as mineral compounds in which 63Cu constitutes 69.1% and 65Cu, 30.9% of the element. Copper is widely distributed in all continents and is present in most living organisms. Although some natural deposits of metallic copper have been found, it is generally mined either as sulphide ores, including covellite (CuS), chalcocite (Cu2S), chalcopyrite (CuFeS2) and bornite (Cu3FeS3); or as oxides, including malachite (Cu2CO3(OH)2); chrysocolla
(CuSiO3·2H2O) and chalcanthite (CuSO4·5H2O).
Because of its electrical properties, more than 75% of copper output is used in the electrical industries. Other applications for copper include water piping, roofing material, kitchenware, chemical and pharmaceutical equipment, and the production of copper alloys. Copper metal is also used as a pigment, and as a precipitant of selenium.
Alloys and Compounds
The most widely used non-ferrous copper alloys are those of copper and zinc (brass), tin (bronze), nickel (monel metal), aluminium, gold, lead, cadmium, chromium, beryllium, silicon or phosphorus.
Copper sulphate is used as an algicide and molluscicide in water; with lime, as a plant fungicide; as a mordant; in electroplating; as a froth flotation agent for the separation of zinc sulphide ore; and as an agent for leather tanning and hide preservation. Copper sulphate neutralized with hydrated lime, known as Bordeaux mixture, is used for the prevention of mildew in vineyards.
Cupric oxide has been used as a component of paint for ship bottoms and as a pigment in glass, ceramics, enamels, porcelain glazes and artificial gems. It is also used in the manufacture of rayon and other copper compounds, and as an optical glass polishing agent and a solvent for chromic iron ores. Cupric oxide is a component of flux in copper metallurgy, pyrotechnic compositions, welding fluxes for bronze and agricultural products such as insecticides and fungicides. Black cupric oxide is used for correcting copper-deficient soils and as a feed supplement.
Copper chromates are pigments, catalysts for liquid-phase hydrogenation and potato fungicides. A solution of cupric hydroxide in excess ammonia is a solvent for cellulose used in the manufacture of rayon (viscose). Cupric hydroxide is used in the manufacture of battery electrodes and for treating and staining paper. It is also a pigment, a feed additive, a mordant in dyeing and an ingredient in fungicides and insecticides.
Amine complexes of cupric chlorate, cupric dithionate, cupric azide and cuprous acetylide are explosive but are of no industrial or public health importance. Copper acetylide was found to be the cause of explosions in acetylene plants and has caused the abandonment of the use of copper in the construction of such plants. Fragments of metallic copper or copper alloys that lodge in the eye, a condition known as chalcosis, may lead to uveitis, abscess and loss of the eye. Workers who spray vineyards with Bordeaux mixture may suffer from pulmonary lesions (sometimes called “vineyard sprayer’s lung”) and copper-laden hepatic granulomas.
Accidental ingestion of soluble copper salts is generally innocuous since the vomiting induced rids the patient of much of the copper. The possibility of copper-induced toxicity may occur in the following situations:
- The oral administration of copper salts is occasionally employed for therapeutic purposes, particularly in India.
- Copper dissolved from the wire used in certain intra-uterine contraceptive devices has been shown to be absorbed systemically.
- An appreciable fraction of the copper dissolved from the tubing commonly used in haemodialysis equipment may be retained by the patient and can produce significant increases in hepatic copper.
- Copper, not uncommonly added to feed for livestock and poultry, concentrates in the liver of these animals and can greatly increase the intake of the element when these livers are eaten. Copper is also added, in large amounts relative to the normal human dietary intake, to a number of pet animal foods that are occasionally consumed by people. Manure from animals with copper-supplemented diets can result in an excessive amount of copper in vegetables and feed grains grown on soil dressed with this manure.
Although some chemical reference works contain statements to the effect that soluble salts of copper are poisonous, in practical terms this is true only if such solutions are used with misguided or suicidal intent, or as topical treatment of extensively burned areas. When copper sulphate, known as bluestone or blue vitriol, is ingested in gram quantities, it induces nausea, vomiting, diarrhoea, sweating, intravascular haemolysis and possible kidney failure; rarely, convulsions, coma and death may result. Drinking of carbonated water or citrus fruit juices which have been in contact with copper vessels, pipes, tubing or valves can cause gastrointestinal irritation, which is seldom serious. Such beverages are acidic enough to dissolve irritating levels of copper. There is a report of corneal ulcers and skin irritation, but little other toxicity, in a copper-mine worker who fell into an electrolytic bath, but the acidity, rather than the copper, may have been the cause. In some instances where copper salts have been used in the treatment of burns, high concentrations of serum copper and toxic manifestations have ensued.
The inhalation of dusts, fumes and mists of copper salts can cause congestion of the nasal and mucous membranes and ulceration with perforation of the nasal septum. Fumes from the heating of metallic copper can cause metal fume fever, nausea, gastric pain and diarrhoea.
Chronic toxic effects in human beings attributable to copper appears only to be found in individuals who have inherited a particular pair of abnormal autosomal recessive genes and in whom, as a consequence, hepatolenticular degeneration (Wilson’s disease) develops. This is a rare occurrence. Most daily human diets contain 2 to 5 mg of copper, almost none of which is retained. The adult human body copper content is quite constant at about 100 to 150 mg. In normal individuals (without Wilson’s disease), almost all of the copper is present as an integral and functional moiety of one of perhaps a dozen proteins and enzyme systems including, for example, cytochrome oxidase, dopa-oxidase and serum ceruloplasmin.
Tenfold, or more, increases in the daily intake of copper can occur in individuals who eat large quantities of oysters (and other shellfish), liver, mushrooms, nuts and chocolate—all rich in copper; or in miners who may work and eat meals, for 20 years or more, in an atmosphere laden with 1 to 2% copper ores dusts. Yet evidence of primary chronic copper toxicity (well defined from observations of patients with inherited chronic copper toxicosis—Wilson’s disease—as dysfunction of and structural damage to the liver, central nervous system, kidney, bones and eyes) has never been found in any individuals except those with Wilson’s disease. However, the excessive copper deposits that are found in the livers of patients with primary biliary cirrhosis, cholestasis and Indian childhood cirrhosis may be one contributing factor to the severity of the hepatic disease that is characteristic of these conditions.
Safety and Health Measures
Workers exposed to copper dusts or mists should be provided with adequate protective clothing to prevent repeated or prolonged skin contact. Where dust conditions cannot be sufficiently controlled, appropriate respirators and eye protection are necessary. Housekeeping and the provision of adequate sanitary facilities is essential since eating, drinking and smoking should be prohibited at the worksite. In mines where there are water-soluble ores such as chalcanthite, workers should be particularly careful to wash their hands with water before eating.
The prevention of metal fume fever is a matter of keeping exposure below the level of concentration currently accepted as satisfactory for working with copper in industry. The employment of local exhaust ventilation (LEV) is a necessary measure to collect copper fumes at the source.
People with Wilson’s disease should avoid employment in copper industries. The serum concentration of ceruloplasmin is a screen for this condition, since unaffected individuals have levels which range from 20 to 50 mg/100 cm3 of this copper protein whereas 97% of patients with Wilson’s disease have less than 20 mg/100 cm3. This is a relatively expensive procedure for broad-based screening programmes.