**4.5 Carcinogenicity**

Presence of heavy metals, dioxins etc. have detrimental effect as they bioaccumulate and interfere with the normal functioning of the cell [40, 47]. Chemically, metals in their ionic form are more reactive and can interact with biological systems in different ways such as cadmium and mercury can readily attach to sulphur in proteins. Apart from this, they are known to mimic and replace essential metals, for instance cadmium can replace zinc and arsenic mimics phosphate. Furthermore, they are known to induce oxidative stress, producing oxidative modification of biomolecules; which might be a key step in the initiation of cancer cells (**Figure 5**) [47].
