Copper was identified as a plant nutrient in the 1930s . Prior to this realization, one of the first uses of copper in agriculture was in chemical weed control . Despite its essentiality, copper is toxic to plants at high concentrations . Uptake of copper by plants is affected by many factors including the soil pH, the prevailing chemical species, and the concentration of copper present in the soil. Once inside the plant, copper is sparingly immobile. Accumulation and expression of toxic symptoms are often observed with root tissues. Extensive use of copper-containing fungicides in localized areas and contamination of soils adjacent to mining operations has created problems of toxicity  in  some  agricultural  regions.  Because  of  this  problem,  remediation  of  copper  and identification of tolerant plant species are receiving increased attention.

COPPER DEFICIENCY AND TOXICITY IN HUMANS

Acquired copper deficiency in adults is quite rare , with most cases of deficiency appearing in premature and normal-term infants . This deficiency can lead to osteoporosis, osteoarthritis and rheumatoid arthritis, cardiovascular disease, chronic conditions involving bone, connective tissue, heart, and blood vessels, and possibly colon cancer. Other copper deficiency symptoms include anemia, neutropenia (a reduction in infection-fighting white blood cells), hypopigmentation (diminished pigmentation of the skin), and abnormalities in skeletal, cardiovascular, integumentary, and immune system functions . In infants and children, copper deficiency may result in anemia, bone abnormalities, impaired growth, weight gain, frequent infections (colds, flu, pneumonia), poor motor coordination, and low energy. Even a mild copper deficiency, which affects a much larger percentage of the population, can impair health in subtle ways. Symptoms of mild copper deficiency include lowered resistance to infections, reproductive problems, general fatigue, and impaired brain function .
Symptoms of copper toxicity, although quite rare, include metallic taste in the mouth and gastrointestinal distress in the form of stomach upset, nausea, and diarrhea. These symptoms usually stop when the high copper source is removed. Because copper household plumbing is a significant source of dietary copper, concern has developed for its contribution to elevated copper levels in drinking water . In most environments, copper concentrations in potable water delivered by copper-containing plumbing tubes are less than 1 mg L  1. Toxicity connected to copper-containing
 

Copper

plumbing pipes is rare, but examples do exist. Toxicity symptoms were traced to contaminated drinking water in new copper plumbing pipes in an incident in Wisconsin . Water levels as high as 3.6 mg Cu L  1  from faucets connected to the new copper-containing pipes were detected. However, flushing the faucet for 1 min before each use decreased copper levels to 0.25 mg L  1. After a few months, a protective layer of oxide and carbonate forms in copper tubing, and the amount of copper dissolved in the water is reduced. Given the population of the United States (almost 300 million people) and the widespread use of copper plumbing (85% of U.S. homes), the health-related cases from high levels of copper in drinking water are extraordinarily rare. In fact, the antimicrobial effects of copper can inhibit water-borne microorganisms in the drinking water that resides in the copper plumbing tubing