Zinc, its sources, functions and threats to the environment and the bilogical life : A review

Zinc is one of the most widespread elements on our planet. Zinc can be found in the environment in many forms, including different isotopic forms, organic and inorganic forms. In both soil and water, zinc can be both of natural and anthropogenic origin. In the soils, both the content and availability of zinc depends on many variables and is a multifaceted issue. Due to its unique structure and properties, zinc is an extremely valuable element for physiological processes. Zinc is a component of more than 200 enzymes involved in fundamental processes such as the synthesis of proteins, nucleic acids and hormones. Zinc-dependent reactions include, amongst others, energy transfer reactions, protein synthesis or nitrogen metabolism. International trends indicate insufficient content/availability of this micronutrient on more than 40% of agriculturally used land. This translates into reduced efficiency in agricultural production and sub-optimal zinc levels in plant tissues, which in turn results in insufficient zinc content in plant-derived food. Optimal zinc content in plant nutrition is crucial from the perspective of both plant physiology and plant production efficiency. Both under- and over-nutrition of zinc will have a negative effect on plant growth, development and performance. One method that is seen as a solution to the problem of zinc deficiency in plant tissues is the use of biofortification. From the point of view of either human health or animal production efficiency, ensuring optimal nutrition of this micronutrient is crucial. Incorrect nutrition of this micronutrient results in disruption of essential metabolic processes, reduced immunity and impaired reproduction as well as progeny development. The purpose of this review is to review the literature and provide a comprehensive overview of the knowledge concerning the sources, functions and risks of zinc in the environment.