Biogeochemical feature of environmental risk assessment

To emphasize our perspective, one should cite a known synonym of ecological risk, a chemical time bomb (CTB). In effect it says that the risk is uncertain as of now, but is both possible and highly probable. 

Practically all the metals are toxic for human health, and the most pronounced 

The term heavy metals includes various elements. Some of them, being nutrients, have essential biochemical functions (Fe, Cu, Zn, Mo, Mn, et al.), whereas these functions are unknown for others (Cd, As, Pb, Hg), and these elements are considered as toxics. One should mention that even the micronutrients consumed by living organisms are required only at microrates and in the greater doses they are also toxic. 

During the 1970s-1980s, a famous catastrophe of human poisoning by mercury and cadmium struck Japan, and this attracted anthropogenic attention to ecological and ecotoxicological problems related to heavy metals. These were uncovered to be influenced by two characteristic peculiarities of the behavior of heavy metals in the environment  

These two factors are responsible for long-term environmental functions of heavy metals and pronounced ecological risk. 

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