Zinc is an essential trace element, meaning small amounts are necessary to maintain health. Zinc helps maintain a healthy immune system and fights the common cold. It is also effective for treating disorders such as attention deficit-hyperactivity disorder, gingivitis, peptic ulcers, osteoporosis and muscle cramping. Additionally, zinc is helpful in treating skin conditions, such as acne and herpes, and can help improve wound healing. Zinc is found naturally in many foods, but can also be supplemented through diet or pills. While the amounts of zinc in our diets are minimal, excessive amounts of pure zinc can be toxic. The Material Safety Data Sheet (MSDS) for zinc describes the hazards associated with pure zinc and the precautions that need to be taken when handling it.
Properties of Zinc
Zinc is an odorless, gray-blue shiny substance that can be granular or lumpy. Zinc is reactive with water and is not volatile at 70 degrees Fahrenheit. The molecular weight of zinc is 65.37 g/mol and its specific gravity is 7.14. The boiling point of zinc is 1665 degrees Fahrenheit and the melting point is 786 degrees Fahrenheit. The vapor pressure of zinc is 1 at 909 degrees Fahrenheit. There is between 0 and 0.1 percent lead in zinc. In moist air, zinc can decompose to hydrogen. In the presence of oxygen, it can decompose to zinc oxide at high temperatures. And when zinc metal is melted, it can produce zinc vapor, which can oxidize and condense in air to form zinc fume.
Hazards Associated with Zinc
The MSDS for zinc rates it as a slight risk for flammability and a moderate risk for reactivity. The health hazards for zinc are rated low on the MSDS; however, if swallowed or inhaled, zinc may cause irritation to the respiratory tract. It may also irritate the skin, eyes, gum tissues, the central nervous system, the kidneys, and the blood and reproductive system. Zinc may form combustible dust concentrations in air. These fumes are highly toxic and may cause fume fever. The dust may also cause symptoms such as coughing, sneezing, or difficulty breathing. If large doses of zinc are ingested, the victim may experience gastrointestinal disturbances such as pain, stomach cramps, and nausea. People with impaired respiratory function or pre-existing skin disorders may be more susceptible to the toxic effects of zinc.
Exposure Controls
Always wear personal protective equipment when working with zinc in the lab. This includes a lab coat, goggles, and gloves. Use a system for local or general exhaust, preferably local, to keep employee exposures below the airborne exposure limits. Local exhaust ventilation can better control the emissions of the contaminant at its source and help prevent its dispersion into the work area. Refer to the American Conference of Industrial Hygienists document, "Industrial Ventilation, A Manual of Recommended Practices," most recent edition, for details. If engineering controls are not feasible and the exposure limit is exceeded, wear a full facepiece particulate respirator -- type N100 filters -- approved by the National Institute for Occupational Safety and Health. These are useful for exposure up to 50 times the exposure limit or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. If lubricants, cutting fluids, glycerine, or other oil particles are present, use a NIOSH type R or P filter. In the case of unknown exposure levels or emergencies, use a full-facepiece positive-pressure, air-supplied respirator. However, in an oxygen-deficient environment air-purifying respirators do not protect workers.
First Aid Measures
In the case of zinc inhalation, move the victim to an area with fresh air. Seek medical attention for difficulty breathing. In the case of ingestion, immediately induce vomiting. In the case of contact with skin, wipe off excess material and flush skin with water for 15 minutes. Remove contaminated clothing and shoes and seek medical attention. Wash clothing and thoroughly clean shoes before reuse. In the case of eye contact, immediately flush eyes with water for 15 minutes, making sure to lift the upper and lower eyelids. Seek medical attention if irritation persists. Never give anything by mouth to an unconscious person.
Handling and Storage
Zinc is stable under ordinary conditions of use and storage. Moist zinc can spontaneously ignite in air. Zinc is incompatible with water, halogens and sulfur. It can also react dangerously with strong oxidizing agents, lower molecular weight chlorinated hydrocarbons, and strong acids and alkalis. Keep zinc in a tightly closed container in a cool, dry, ventilated area. Keep away from heat, moisture and incompatibilities, and protect containers from physical damage. Take care to observe all precautions and warnings for the product as even empty containers may be hazardous due to remaining product residues. Before handling accidental spills, ensure that clean-up personnel are wearing personal protective clothing including a dust/mist respirator. Immediately remove all sources of ignition as the substance may self-ignite. Mildly ventilate the area of spill. Sweep or vacuum the spill, taking care not to disperse zinc powder into the air. Place the zinc in a closed container for disposal or recovery. Report any spills and releases to soil, water and air in excess of reportable quantities to the U.S. Coast Guard National Response Center. Any zinc waste that cannot be recovered or recycled should be handled as hazardous waste and sent to a Resource Conservation and Recovery Act approved waste facility. Check state and local disposal regulations and dispose of container and unused contents in accordance with federal, state and local requirements.
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