Biomagnification and bioremediation of arsenic in affected regions of murshidabad district

Arsenic contamination of soil and drinking water is one of the major problems of the modern world. In India, the state of West Bengal is severely affected by Arsenic toxicity. Nine districts of West Bengal are arsenic affected. Amongst them, Murshidabad shows very high levels of Arsenic in ground water and soil. U U.S. Environmental Protection Agency and WHO has set the recommended limit of arsenic to 10 ug/l in drinking water. In India, permissible limit of arsenic is 50 ug/l, in the absence of any alternative source of drinking water. In Murshidabad district, Blocks situated in the western side of Bhagirathi river are less affected by Arsenic toxicity (30.1% above 10 ug/l and 11.7% above 50 ug/l) than the blocks located on the eastern side (64.7% above 10 ug/l and 32.5% above 50 ug/l). The most common and toxic forms of arsenic are arsenate and arsenite. Arsenite is more toxic than arsenate. Both arsenite and arsenate are soluble, but arsenite has a higher solubility, bioavailabilty and mobility than arsenate. Skin lesions are signs of advanced stages of arsenic poisoning. Long term intake of arsenic causes cancer of skin, lung, liver, bladder and kidney. Other adverse health effects include pulmonary diseases, neurotoxicity, diabetes, cardiovascular diseases and developmental defects. Bioremediation is a natural process in which living organisms like bacteria, fungi, algae and plants are used to degrade or transform hazardous organic contaminants, or to reduce the toxicity of inorganic contaminants. Certain microorganisms are resistant to arsenic toxicity. Some of them use arsenite oxidase enzyme to convert arsenite (more toxic form) to arsenate (less toxic). The genes encoding proteins important for arsenite oxidation reside in an operon, named as aox operon. Biomagnification is a process where the concentration of certain substances moves up in a food chain. Rice accumulates arsenic into the grains, much more efficiently than any other staple cereal crops. To combat this, transgenic rice plants could be developed, where the genes involved in the pathway of uptake of arsenic could be mutated, so that bioaccumulation of arsenic does not take place in rice.