ABSTRACT
An escalating rise in urbanization and population dynamics has established a large number of industries releasing toxic metals into the environment. These metals have a wide range of applications in agricultural, domestic, industrial, medical, pharmaceutical, and technological aspects, resulting in their extensive circulation in the environment. Primary threats to the flora, fauna, and human health are associated with the most toxic metals in the environment, that is, arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and silver (Ag) as reviewed by the World Health Organization (WHO). Biological factors such as species characteristics, trophic interactions, and physiological adaptation play an important role in deducing the presence of metal in the environment. Metal toxicity is dependent on diverse factors such as dosage, route of exposure, presence of chemical species, age, gender, genetics, and nutritional status of the exposed individuals. On exposure, they cause various organ deformities and restrict normal physiological functions of the body. Many conventional strategies have been practiced for reducing their toxicities; however, several challenges have led to limited field implementation of these techniques. The use of microbes is a cheaper alternative for achieving remediation by converting highly toxic metals to less-toxic/nontoxic forms and can also be utilized for large-scale metal removal. Therefore, this chapter summarizes the environmental occurrence, global toxicity, and potential human adversities caused by the most toxic metals in the environment and their strategic conventional and bioremediation treatment approaches.
