ABSTRACT
Pollution is referred to as the presence of undesirable substances, such as inorganic (heavy metals) and organic pollutants (hydrophobic organic compounds). Heavy metals even at picomolar concentrations are extremely toxic in nature, and they are nondegradable, unlike other organic pollutants. Sources of heavy metal pollution can be (i) natural, such as geothermal activities, comets, space dust and volcanic activities, or (ii) anthropogenic sources, such as rapid industrialisation, extensive use of hydrocarbons, chlorinated hydrocarbons, chemical pesticides, etc. and (iii) e-waste. Due to the aforesaid activities, toxic metals, such as lead (Pb), chromium (Cr), nickel (Ni), cadmium (Cd), copper (Cu), zinc (Zn), arsenic (As) and mercury (Hg), are dumped into the environment. Because of their nonbiodegradable nature, they are a persistent threat to our life and environment (Singh and Cameotra 2004). In addition, these metals can enter into the food chain and can accumulate in the human body leading to birth defects, mental and physical retardation, cancer, etc. (Singh et al. 2010).
