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General Characteristics
Zinc is one of the most common elements in the earth's crust. It is present in nearly all foods. Also found naturally in air, soil, and water, it is commercially used to produce such products as dry cell batteries, alloys like brass and bronze, and coatings to prevent rust. In its pure elemental form, zinc is a blue-white shiny metal. Powdered zinc is explosive and may burst into flames if stored in damp places.
Zinc combines with elements such as chlorine, oxygen, and sulfur to form compounds. Some of the most familiar compounds are zinc chloride, zinc oxide, zinc sulfate, and zinc sulfide. These substances are used by the drug industry as ingredients in common products like sun blocks, diaper rash ointments, and deodorants. Some zinc compounds also end up in residual waste and require management at hazardous waste treatment and disposal facilities.
Hazard Summary
Zinc can negatively affect health in large doses. It results in such physical symptoms as stomach cramps and nausea. Ingesting high levels of zinc for several months may lead to anemia, damage to the pancreas, and decreased levels of cholesterol. It is not known if high levels of zinc affect the ability of women to reproduce or cause birth defects in humans.
Inhaling large amounts of zinc may cause a specific short-term disease called metal fume fever. Inhalation can occur from exposure to zinc dust, or smelting or welding fumes. However, very little is known about the long-term effects of breathing zinc dust or fumes.
Consuming too little zinc is also a concern. Without enough zinc in the diet, people may experience loss of appetite, decreased sense of taste and smell, impaired immune function, slow wound healing, or skin sores.
The Department of Health and Human Services, the International Agency for Research on Cancer, and the Environmental Protection Agency (EPA) have not classified zinc as carcinogenic.
Environmental Impact
Zinc can enter the air, water, and soil as a result of both natural processes and human activities. Natural releases to air are mainly due to volcanic emissions and forest fires. Zinc can also enter the environment as the result of various industrial processes through air and/or water emissions. Some processes of concern are events such as spills and unpermitted discharges and the excessive use of zinc compounds in products applied to land, like zinc fertilizers. Fine zinc dust particles in the air are transferred to soil and bodies of water by rain or snow. Most of the zinc in bodies of water settles to the bottom. However, a small amount may remain either dissolved in water or as finely suspended particles.
Environmental Controls
Zinc emissions in industrialized countries have decreased during the last few decades. Reasons for this reduction include effective control of point source emissions. In addition, there is a general decrease in atmospheric SO2, which has resulted in lower zinc corrosion rates.
Zinc present in waste materials is also safely controlled if managed at permitted waste facilities. Zinc compounds can be treated with specialized chemicals that prevent the release of metals to the environment. These treated wastes are then placed in state-of-the-art landfills that are equipped with multiple liners and leak detection systems. This combination of steps is highly protective of human health and the environment.
If zinc is present in waste at high concentrations, it can be reclaimed for reuse. However, the zinc recycling process results in wastes that often contain concentrated quantities of other hazardous materials. These materials can threaten human health and the environment if they are not managed at a permitted facility.
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