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Over six million people in nine districts of West Bengal, India are exposed to very high levels of arsenic primarily through their drinking water. More than 300,000 people showed arsenic-induced skin lesions in these districts. This is regarded as the greatest arsenic calamity in the world. Chronic arsenicosis causes varied dermatological signs ranging from pigmentation changes, hyperkeratosis to non-melanocytic cancer of skin, and also malignancies in different internal organs. Higher incidences of opportunistic infections are found in the arsenic-exposed individuals, indicating that their immune systems may be impaired somehow. We have thus investigated the effect of arsenic on T-cell proliferation and cytokine secretion in 20 individuals with arsenic-induced skin lesions and compared the results with 18 arsenic-unexposed individuals. A marked dose-dependent suppression of Concanavalin A (Con A) induced T-cell proliferation was observed in the arsenic-exposed individuals compared with the unexposed (P < 0.001) individuals. This correlated with a significant decrease in the levels of secreted cytokines by the T cells (TNF-α, IFN-γ, 1L2, IL10, 1L5, and 1L4) in the exposed individuals (P < 0.001). Thus it can be inferred that arsenic exposure can cause immunosuppression in humans. [ABSTRACT FROM AUTHOR]

Copper dust from the Indian Copper Complex, Ghatsila is water leached and the residue is subjected to leaching by sulphuric acid solution. Effects of various parameters on H2SO4 leachings of water leached residue (WLR) and as received copper dust have been investigated to obtain optimum conditions for leaching. Under optimum conditions, bulk leachings of WLR and as received copper dust by H2SO4 solutions have been carried out. Leaching of 150 g WLR by 1 dm3 of 15% (v/v) H2SO4 at 353 K for 4 h under reflux yields 1 dm3 leached solution containing 43·12, 16·20, 22·14, 0·40, 0·02, 0·04 and 0·12 g dm-3 Cu2+, Fe2+, Fe3+, Zn2+, Co2+, Ni2+ and Al3+ respectively, together with 0·90M unreacted H2SO4. Also, leaching of 160 g as received copper dust by 1 dm3 of 10% (v/v) H2SO4 at 353 K for 4 h under reflux yields a leach solution containing 44·30, 9·00, 15·70, 0·40, 0·15, 0·03 and 0·11 g dm-3 Cu2+, Fe2+, Fe3+, Zn2+, Co2+, Ni2+ and Al3+ respectively, together with 0·90M free H2SO4. The iron contents of these solutions have been reduced to the levels of <0·5 g dm-3 by applying D2EHPA extraction–oxalic acid stripping technique so that the solutions can be used as electrolytes in electrorefining, electrowinning or hydrogen reduction of copper. [ABSTRACT FROM AUTHOR]

Copper dust from ICC, Ghatsila (India) was characterised and water leached. Water leaching at room temperature for 1 h dissolves as much as 50% copper present in the sample. The water leach residue, consisting mostly of oxides, was moistened with H2SO4 then baked (sulphatising roasted) in static conditions for 30 min at 973 K. The baked mass was found to contain CuSO4, CuSO43H2O, CuSO45H2O, Cu2O(SO4) and Fe2O3. Copper in the baked mass can be leached quantitatively in 1 h at room temperature by even 0·1% H2SO4 solution. Optimum conditions of baking and leaching for the highest recovery of copper have been determined. The solutions obtained by sulphuric acid leaching of water leached and baked material contain about 2-3 g/l iron in both ferrous and ferric states. This iron can be largely precipitated out by adding lime to adjust the pH to 3·60 followed by passing air through the solution at 353 K for 4 h. The precipitate can easily be separated by filtration and the filtrate is of electrorefining electrolyte grade containing 44·05 g/l copper and 0·9 g/l iron. The iron content may further be reduced to 0·63 g/l by single stage extraction using 0·05 M D2EHPA solution. [ABSTRACT FROM AUTHOR]