Heavy metals/metalloids in food crops and their implications for human health

Abstract

In general, metals are elements that are hard, lustrous, fusible, malleable, ductile, and have good electrical and thermal conductivity. An element without the characteristics of a metal is referred to as a nonmetal. An element with properties halfway between those of metals and nonmetals is said to be a metalloid. Heavy metals are ubiquitous and naturally occurring elements that cannot be degraded or destroyed. Heavy metals and/or metalloids are generally referred to any naturally occurring metallic chemical element having an atomic number greater than 20, a relatively high atomic weight in the range of 63.5-200.6 g mo1-1 and the density at least five times of water (5gcm-3) (Koller and Saleh 2018). Heavy metals and/or metalloids include arsenic (As), cadmium (Cd), mercury (Hg), chromium (Cr), thallium (TI), lead (Pb), aluminum (Al), etc. Heavy metals can be broadly classified into two categories: essential and nonessential. Essential heavy metals are required by living organisms for carrying out fundamental processes viz. growth, metabolism, and development of different organs. [Excerpt from the Introduction]