Copper is an essential trace element which is ubiquitous in earth’s crust. The main sources of copper are its sulphide and oxide ores from which the metal is extracted by roasting, smelting and electrolytic refining. There are substantial deposits of copper in Rajasthan, India, which have been estimated to contain about 200 million tons of copper.
The tough but malleable and soft metal is highly resistant to corrosion and is next only to silver in electrical conductivity. Hence copper finds widespread use in industries next only to iron and aluminium. It is used widely in dyes, paints, pigments, ceramics, in many pesticides and some therapeutical preparations as well. Copper contamination of the environment is largely due to its release by industrial units producing non-ferrous metals, fertilizers, disposal of tailings or the solid wastes from mines and from flyash produced by combustion of coal and organic matter.
Copper is necessary for the normal biological activity and its deficiency is characterised by nypochromic microlytic anaemia which develops as a consequence of defective haemoglobin synthesis. Copper is required in most of the oxidative enzymes such as catalases, peroxidases etc. and is also an essential part of several enzymes such as tyrosinase which is involved in the formation of melanin, super oxide dismutase, amine oxidase, urease and cytochrome oxidase.
The recommended daily intake of copper ranges from 2.0 to 3.0 mg in humans. It is mainly through food and water that humans take up copper. Soluble copper concentration in drinking water ranges between 1.5 to 2.4 µg per litre in urban areas while in rural areas it is usually well below 1 µg per litre.
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Meat, fish, oysters and dried legumes contain a high concentration of copper while cereals and milk are poor in their copper content. Copper residues are generally higher in marine fishes as compared to fresh water ones. The concentration of copper in ambient air in Bombay city ranges between 0.20 to 0.85 (µg per cubic metres which is well below the dangerous level (Khandekar et al, 1980).
Workers involved in spraying of Bordeax mixture (an insecticide with copper) on grapes and other crops develop acute irritation of respiratory tract and metal fume fever characterized by the development of interstitial, pulmonary lesions and nodular fibro-hyaline scars containing deposits of copper. Lung cancer may also develop in many cases. An ingestion of about 50-80 mg of copper causes gastro-intestinal disturbances, nausea, vomiting etc. Larger quantities, taken accidentally or intentionally may cause haemolysis hepato-toxic and nephrotoxic effects.
In plants low levels of copper are essential for normal activity of a number of enzymes and for chlorophyll synthesis. However, at a slightly higher concentration copper is the most toxic element after mercury. Inhibition of growth occurs at concentrations less than 0.1 ppm in majority of plant species. Uptake of copper by plants is accelerated in presence of calcium and magnesium ions but diminishes with fall in pH. A higher concentration of copper is injurious to blue green algae since this metal tends to suppress nitrogen fixation.