and non-essentials include Hg, Pu, Cd and Pb (Bhattacharya, Misra, and Hussain 2016; Kumar, Smita, and Cumbal Flores 2017; Tchounwou et al. 2012), which are harmful even at low concentrations (Kumar, Smita, and Cumbal Flores 2017; Tchounwou et al. 2012).