Zinc
Zinc is a lustrous bluish-white metal. It is found in group IIb of the periodic table. It is brittle and crystalline at ordinary temperatures, but it becomes ductile and malleable when heated between 110°C and 150°C. It is a fairly reactive metal that will combine with oxygen and other non-metals, and will react with dilute acids to release hydrogen.
Applications:
It is used principally for galvanizing iron, more than 50% of metallic zinc goes into galvanizing steel, but is also important in the preparation of certain alloys.
It is used for the negative plates in some electric batteries and for roofing and gutters in building construction. Zinc is the primary metal used in die casting in the automobile industry.
As a pigment zinc is used in plastics, cosmetics, photocopier paper, wallpaper, printing inks etc. while in rubber production its role is to act as a catalyst during manufacture and as a heat disperser in the final product.
Zinc in the environment
Zinc is a very common substance that occurs naturally. Many foodstuffs contain certain concentrations of zinc. Drinking water also contains certain amounts of zinc, which may be higher when it is stored in metal tanks. Industrial sources or toxic waste sites may cause the zinc amounts in drinking water to reach levels that can cause health problems.
Zinc occurs naturally in air, water and soil. Most zinc is added during industrial activities, such as mining, coal and waste combustion and steel processing.
The main zinc mining areas are Canada, Russia, Australia, USA and Peru. World production exceeds 7 million tons a year and commercially exploitable reserves exceed 100 million tons.
Health effects of zinc
Zinc is a trace element that is essential for human health. When people absorb too little zinc they can experience a loss of appetite, decreased sense of taste and smell, slow wound healing and skin sores. Zinc-shortages can even cause birth defects.
Although humans can handle proportionally large concentrations of zinc, too much zinc can still cause eminent health problems.
In the work place environment zinc contagion can lead to a flu-like condition known as metal fever. This condition will pass after two days and is caused by over sensitivity.
Zinc can be a danger to unborn and newborn children. When their mothers have absorbed large concentrations of zinc the children may be exposed to it through blood or milk of their mothers.
Effects of zinc on the Environment
The world's zinc production is still rising. This basically means that more and more zinc ends up in the environment.
Water is polluted with zinc, due to the presence of large quantities of zinc in the wastewater of industrial plants. This wastewater is not purified satisfactory. One of the consequences is that rivers are depositing zinc-polluted sludge on their banks. Zinc may also increase the acidity of waters.