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Metals naturally exist in the crust of the earth, and their compositions vary among different localities, resulting in structural disparity of surrounding concentrations. Some heavy metals are much important in trace amounts in respect to living organisms related to their metabolic activities. High solubility of various heavy metals changes them into extremely toxic and perilous contaminant of water and soil when discharged by many industrial activities. When these metals are released into the environment, they can be leached into the underground waters, depositing in the aquifers, or run off into surface waters and soils thereby resulting in water and soil pollution. Thus, heavy metals become a potential contaminant for environment that can partake in trophic transfer in food chains. The toxicity of heavy metals mainly depends upon its relative oxidation state, which is responsible for physiological bio-toxic effects. When these metals enter into the living organisms, they, combine with proteins, enzymes, and DNA molecules, form highly stable biotoxic compounds, thus altering their proper functioning and obstructing them from the bioreactions. Arsenic, chromium, cadmium, and lead are highly toxic and produce mutagenic, carcinogenic, and genotoxic effects. Hence, this chapter is focused on occurrence and allocation of heavy metals, their toxicological impact on environment, and their possible eco-friendly remedies for green and healthy environment.

Chromium is one of the major inorganic environmental pollutants, which is added in the environment through various natural and anthropogenic activities and exists mainly in two forms: Cr(III) and Cr(VI). Cr(VI) is considered to be more toxic than Cr(III) due to its high solubility and mobility. It is a well-reported occupational carcinogen associated with lung, nasal, and sinus cancers. Thus, this review article provides the detailed information on the occurrence, sources of chromium contamination in the environment and their toxicological effects in human, animal, plants as well as in microorganisms, and bioremediation strategies to minimize the toxic effects.

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