ABSTRACT

The rapid increase in population together with fast industrialization causes serious environmental problems, including the production and release of considerable amounts of toxic metals in the environment (Sarma 2011). Most of the toxic metals are heavy metals (HMs), which are ascribed to transition metals with atomic masses over 20 and having a speci—c gravity of above 5 g cm−3 or more. However, in biology, “heavy” refers to a series of metals and metalloids that can be toxic to both plants and animals even at very low concentrations (Rascio and Navari-Izzo 2011). Although HMs are thought to be synonymous with toxic metals, lighter metals, such as aluminum (Al), also have toxicity, and not all HMs are particularly toxic. Some are essential, such as iron (Fe), copper (Cu), zinc (Zn), and molybdenum (Mo). Therefore, the de—nition may also include trace elements when considered in abnormally high, toxic doses. A difference is that there is no bene—cial dose for a toxic metal with a biological role. HMs are ubiquitous environmental contaminants in industrialized civilizations throughout the world. Because of rising environmental pollution in industrial areas, toxicity of various HMs for living organisms has become a matter of utmost global concern (Dubey 2011). Over the last few decades, we have witnessed a dramatic, troublesome increase in HM contamination in the environment globally. It would appear that humans are the only ones to be blamed because anthropogenic activities are the main source of the pollution that is causing the contamination (Gratão et al. 2005; Azevedo and Azevedo 2006). Extreme levels of metals in the water and soil may come up because of a range of activities, such as mining; metal industries; road traf—c; power stations; burning of fossil fuels; crop production; animal rearing, including wastewater; use of agrochemicals; waste disposal; and so on (Dubey 2011). Contamination of soil with metals leads to losses in agricultural yield and are a threat to the health of wildlife and humans (Sharma and Dubey 2007; Sharma and Dietz 2008).