Zinc is the 24th most abundant element in the Earth’s crust and has been present ever since the planet formed its surface. It is an essential mineral of “exceptional biologic and public health importance” and is considered a “Life Saving Commodity” by the United Nations.
Zinc moves constantly throughout the environment by a process called natural cycling. Rain, snow melt, ice, solar heat, and wind erode zinc from rocks and soil. Wind and water carry minute amounts of zinc to lakes, rivers and the sea, where it collects on organic material and eventually settles into the sediment. Other natural phenomena, such as volcanic eruptions, forest fires, dust storms and sea spray, contribute to the continuous cycling of zinc.
The concentration of zinc in nature without the additional influence of human activities is called “natural background.” The natural background levels in surface water, soil and rock vary over a wide range of concentrations, although the variable range is relatively consistent from place to place. The natural amount of zinc in rivers has been measured from less than 5 to over 100 micrograms per litre. These ranges are consistent across different regions and have been comprehensively documented throughout the world. The zinc contained in soils directly influences background concentrations found in rivers. Natural levels in soil can range from less than 10 to over 1000 milligrams per kilogram.
It is estimated that natural emissions, including the mobilization of zinc due to uptake by plants, collectively amounts to over 10 million metric tons of zinc each year. Human activities do not add to the overall zinc amount on a global scale, but mining, production of goods and the use of zinc create situations where emissions to the atmosphere, soil and water can occur. These are known as anthropogenic emissions. Over the last few decades, zinc emissions from zinc manufacturing and processing have been reduced substantially by process improvements and the progressive implementation of more efficient emission abatement techniques. As a result, present-day emissions from industrial processes are limited and are estimated to be only 10% of the total emissions from the natural cycling of zinc from erosion, sea spray, volcanic eruptions, etc. Members of the International Zinc Association adopted a set of commitments to sustainability as set out in their Sustainability Charter. For more information visit www.zinc.org/sustainability.
The environmental impact of zinc – and of all essential elements – cannot be assessed in the same way as man-made chemical compounds. Because zinc occurs naturally, eliminating it from the environment would not be possible. Moreover, because zinc is essential to life, achieving such a goal would ultimately lead to detrimental effects throughout an ecosystem. In other words, ‘less’ is not necessarily ‘better’.
For essential elements such as zinc, environmental concentrations and their effects must be considered within the context of an organism’s natural ability to regulate (uptake and excretion) and maintain a certain level of homeostasis. Organisms have evolved mechanisms to supply their needs independent of the external concentration by regulating an essential element to a constant internal level. Environments containing zinc at very low or very high concentrations may produce undesirable effects and the range between the minimum and maximum is often called the optimal window of essentiality.
Zinc is essential for human health and is found in all parts of the body. It is a component in more than 300 enzymes, plays a key role in the human metabolism and influences hormones. Zinc is vital for the stabilisation of DNA and the expression of genes as well as for the transfer of nerve signals.
Zinc is important for activating normal growth and neurological development in infants, children and teenagers. It accelerates cell division and enhances the immune system. It is also important in protecting the body from illnesses and fighting infections, such as reducing the duration and severity of a common cold and halting diarrhea.
Zinc deficiency is a major health problem in developing countries, especially among young children. Zinc deficiency weakens their immune system and leaves them vulnerable to conditions such as diarrhea, pneumonia and malaria. Due to the impact zinc can have in saving children’s lives, the former UN Secretary General Ban Ki-Moon named zinc a “life-saving commodity”. In light of this global health issue, the zinc industry, through International Zinc Association, launched the Zinc Saves Kids initiative in support of UNICEF‘s global micronutrient supplementation program to address zinc deficiency for at-risk children. For more information on the Zinc Saves Kids initiative visit zincsaveskids.org.
As well as being key for human health, zinc is a beneficial micronutrient for crops and zinc deficiency takes an enormous toll on both humans and agricultural crop productivity.
Zinc is lacking in 50% of the world’s soils and is recognized as the most common micronutrient deficiency in crops. Zinc deficiency in soils creates reductions in crop yield, crop quality and nutritional value. Adding zinc to soils is a sustainable approach to significantly increasing crop yield, boosting nutritional value in humans and improving farmer incomes.