Explain about the Zinc Toxicity?

Only a few occurrences of acute zinc poisoning have been reported. The toxicity signs are nausea, vomiting, diarrhoea, fever and lethargy and have been observed after ingestion of 4-8 g (60-120 mmol) of zinc. Gross acute zinc toxicity has been reported after consuming water stored in galvanized containers. Symptoms include nausea, vomiting and fever. These symptoms are observed after ingestion of 2g or more of zinc. Long-term zinc intakes higher than requirements could, however, interact with the metabolism of other trace elements. Copper seems to be especially sensitive to high zinc doses.

A zinc intake of 50 mg/day (760 μmol) affects copper status. Because copper also has a central role in immune defence, these observations should be studied further before large-scale zinc supplementation programmes are undertaken. Any positive effects of zinc supplementation on growth or infectious diseases could be offset by associated negative effects on copper-related functions. Intakes between 25 -50 mg zinc per day have been reported to interfere with metabolism of both iron and copper. FAONHO 2004 therefore recommended the upper level of zinc intake for an adult man at 45 mg/day (690 μmol/day) and extrapolated to other groups in relation to basal metabolic rate. For children, this extrapolation means an upper limit of intake of 23-28 mg/day (350-430 μmol/day), which is close to what has been used in some of the zinc supplementation studies. Except for excessive intakes of some types of seafood, such intakes are unlikely to be attained with most diets. Adventitious zinc in water from contaminated wells and from galvanized cooking utensils could also lead to high zinc intakes.