Microbe-mediated management of arsenic contamination: current status and future prospects

Abstract

Arsenic (As) contamination is an issue recognized as a serious risk throughout the world. Among several oxidation states of As existing in the environment, like arsenate [As (V)], arsenite [As (III)], elemental As [As (0)] and arsenide, toxicity of As (III) is 25–60 times more than As (V). Over the period the accumulation of As in the environment has increased several folds thereby contaminating the soil and resulting in biomagnification affecting the food chain. As-contaminated drinking water and its accumulation in food leads to its long term exposure and is a threat not only to human health but to animals and plants also. Toxicity of As in animals and humans via food warrants in developing appropriate regulatory measures as well as remediation of As contaminated environments by feasible technologies. Commonly in such cases As removal is done by the chemical based conventional techniques such as precipitation, oxidation and reduction as well as ion exchange, filtration and reverse osmosis. Such techniques are not only costly but also have drawbacks on account of removal accuracy and are not environment-friendly as they result in secondary pollution caused by chemicals used in the process. There is need for development of affordable, environment friendly and sustainable options of remediation in which microorganisms can provide an aid. Capability of microorganisms for transformation of As into various oxidation states with different solubility, mobility and toxicity can be used in As bioremediation strategies. The biological metabolic properties of the microbes which make them able to survive in high exposure of As need to be explored and exploited in developing cost effective and sustainable large-scale As remediation bio-systems.