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Chromium Case Study

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Introduction
All sectors of our society like industry, agriculture, construction, mining and transportation generate wastes. Industrial wastes are generated from different industrial process and the level of toxicity of waste depends on industrial process. Among all industrial wastes tannery waste ranked as the highest pollutants. Because of low labour and material cost tannery activity occurs in low and middle income countries. Between 1970 to 1995 production of leather from low income and middle income country increases from 37% to 58% and from 29% to 59% respectively. According to Blacksmith institute approximately 75% of chromium polluted site are situated in South Asia and high concentration of chromium in South Asia is due to abundance
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Chromium and its compounds are placed on priority list of toxic chemicals by US EPA (Cheung and Gu, 2005; Thacker et al., 2006). Chromium is essential trace element for all living organism. The valency state of chromium ranges from -2 to +6 out of which only hexavalent and trivalent forms are more stable. Trivalent form is necessary for proper glucose and fat metabolism and required for proper functioning of insulin (Krishna and Philip 2005). But increase in its concentration can cause several consequences such as growth and development abnormalities, lung cancer, chromate ulcer, kidney damage skin irritation and wide range of other illness (Thiele 1995). Chromium exist in two stable oxidation state in environment Cr6+ and Cr3+ out of these two Cr6+ is more toxic and able to transport across the cell membrane. Due to its structural similarity with sulphate, chromate uses sulphate transporters for their entery inside the cytoplasm. Hexavalent form of chromium itself not able to bind with DNA, RNA and Proteins inside cytoplasm firstly it reduced into Cr3+ which show binding ability with these molecules. During reduction of Cr6+ to Cr3+ it generates reactive oxidation species which damage DNA.
Chromium associated pollution is of increasing concern now days. Some conventional methods for treatment of chromium includes chemical precipitation, ion exchange, filtration, adsorption, electro chemical precipitation
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