This guideline summarizes pertinent information about zinc oxide for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.

SUBSTANCE IDENTIFICATION

* Formula

ZnO

* Structure

(For Structure, see paper copy)

* Synonyms

Amalox, calamine, felling zinc oxide, zincite, zinc white, AZO 22, emar, outmine, pasco

* Identifiers

1. CAS No.: 1314-13-2

2. RTECS No.: ZH4810000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Zinc oxide is an odorless, amorphous, white or yellowish-white powder.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 81.37

2. Boiling point: Data not available.

3. Specific gravity: 5.607 at 20 degrees C (68 degrees F) Windholz 1983, p. 1457; NLM 1992]

4. Vapor density: Data not available.

5. Melting point: 1975 degrees C (3587 degrees F)

6. Vapor pressure: Data not available.

7. Solubility: Practically insoluble in water; soluble in dilute acetic or mineral acids, ammonia, ammonium chloride, ammonium carbonate, and fixed alkali solutions; insoluble in alcohol.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Contact between zinc oxide and chlorinated rubber, linseed oil, magnesium, hydrogen fluoride, aluminum + hexachloroethane, zinc chloride or phosphoric acid, and water should be avoided.

3. Hazardous decomposition products: Toxic gases such as zinc oxide fumes may be released in a fire involving zinc oxide.

4. Special precautions: Zinc oxide will absorb carbon dioxide from the air and form zinc carbonate. Prolonged contact with water will cause zinc oxide to slowly decompose.

* Flammability

Zinc oxide is not combustible.

The National Fire Protection Association has not assigned a flammability rating to zinc oxide.

1. Flash point: Not applicable.

2. Autoignition temperature: Not applicable.

3. Flammable limits: Not applicable.

4. Extinguishant: Use an extinguishant that is suitable for the materials involved in the surrounding fire.

Fires involving zinc oxide should be fought upwind from the maximum distance possible. Isolate the hazard area and deny access to unnecessary personnel. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving zinc oxide.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for zinc oxide is 15 milligrams per cubic meter (mg/m(3)) of air for total dust, ()and 5 mg/m(3) for the respirable fraction as an 8-hour time-weighted average (TWA) concentration [29 CFR 1910.1000, Table Z-1].

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established recommended exposure limits (RELs) for zinc oxide of 5 mg/m(3) for total dust as a TWA for up to a 10-hour workday and a 40-hour workweek and a 15 minute ceiling of 15 mg/m(3) [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned zinc oxide a threshold limit value (TLV) of 10 mg/m(3) for total dust (containing no asbestos and <1% crystalline silica), as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH has assigned a TLV-TWA of 5 mg/m(3) and a TLV-STEL of 10 mg/m(3) to zinc oxide fume [ACGIH 1994, p. 36].

* Rationale for Limits

The NIOSH limit is based on the risk of metal fume fever [NIOSH 1992].

The ACGIH limit is based on providing reasonable control of this nuisance dust [ACGIH 1991, p. 1756].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to zinc oxide can occur through inhalation, ingestion, and eye or skin contact.

* Summary of toxicology

1. Effects on Animals: Zinc oxide can affect the lungs and the reproductive system in experimental animals; it is also an experimental mutagen. Topical administration of zinc oxide to rabbits, mice, and guinea pigs failed to cause either skin irritation or signs of systemic toxicity [ACGIH 1991, p. 1754]. The oral LD(50) in mice is 7,950 mg/kg [NIOSH 1991]. The LC(50) in mice is 2,500 mg/m(3) (duration not provided) [NIOSH 1991]. Guinea pigs exposed to 1,000 to 2,600 mg/m(3) zinc oxide for one hour had initial hypothermia followed by an increase in body temperature 6 to 18 hours later [ACGIH 1991, p. 1754]. Rats inhaling 2,500 mg/m(3) for three to four hours died either during or immediately after the exposure [ACGIH 1991, p. 1754]. During a 1-hour inhalation study, guinea pigs inhaling 0.7 mg/m(3) showed no change in pulmonary airway resistance. Progressive diminution in lung compliance was observed in these animals [ACGIH 1991, p. 1754]. Guinea pigs exposed to 5 or 7 mg/m(3) zinc oxide fume for 3 hours/day for 5 and 6 days, respectively, had transient changes in pulmonary function with small airway inflammation and edema. These animals showed reduced total lung capacity, vital capacity, and carbon monoxide diffusion capacity. No adverse effects were observed in guinea pigs exposed to zinc oxide fume at a concentration of 2.7 mg/m(3) [ACGIH 1991, p. 1754]. In a teratogenicity study, rats were administered 100 or 200 mg/kg/day zinc oxide for 21 days prior to mating and throughout pregnancy. Increased fetal deaths and reduced fetal body weights were reported for the 200 mg/kg/day group, but no adverse effects were observed at 100 mg/kg/day [ACGIH 1991, p. 1754]. Zinc oxide was mutagenic in in vitro test systems [NIOSH 1991].

2. Effects on Humans: Zinc oxide dust is primarily a nuisance dust, but exposures to high concentrations can result in respiratory system effects in humans. Volunteers inhaling 600 mg/m(3) zinc oxide dust for 10 minutes exhibited persistent rales, decreased vital capacity, coughing, upper respiratory tract irritation and substernal pain. Studies have reported that exposures to concentrations up to 430 mg/m(3) zinc oxide, resulted in chest pain [ACGIH 1991, p. 1755]. Inhalation of zinc oxide fume can result in metal fume fever. This in a self limiting condition characterized by flu-like symptoms which resolve within 24 to 48 hours [ACGIH 1991, p. 1755]. Repeated exposures to zinc oxide by skin contact have resulted in papular-pustular skin eruptions in the axilla, inner thigh, inner arm, scrotum and pubic areas [ACGIH 1991]. Epidemiologic studies of zinc refinery workers found no correlation between industrial zinc exposures and lung or other types of cancer [ACGIH 1991].

* Signs and symptoms of exposure

1. Acute exposure: Acute exposure to zinc oxide can result in coughing, substernal pain, upper respiratory tract irritation, rales, chills, fever, nausea, and vomiting.

2. Chronic exposure: Chronic exposure to zinc oxide by skin contact may result in papular-pustular skin eruptions in the axilla, inner thigh, inner arm, scrotum and pubic areas.

EMERGENCY MEDICAL PROCEDURES

* Emergency medical procedures: [NIOSH to supply]

5. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard [29 CFR 1910.1200]). All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve zinc oxide and lead to worker exposures to this substance:

• The manufacture and transportation of zinc oxide
• Use as a white pigment in rubber formulations and as a vulcanizing agent
• Use in cosmetics, ointments, and electronic devices
• Use as a UV absorber in plastics, ceramics, floor tile, and glass
• Use in seed treatments, food additives, photoconductors, and in color photography

Methods that are effective in controlling worker exposures to zinc oxide, depending on the feasibility of implementation, are as follows:

• Process enclosure
• Local exhaust ventilation
• General dilution ventilation
• Personal protective equipment

Workers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR 1910.120].

Good sources of information about control methods are as follows:

1. ACGIH [1992]. Industrial ventilation--a manual of recommended practice. 21st ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne zinc oxide is made using a tared low ash polyvinyl chloride filter (5 microns) preceded for respirable fraction sampling by a 10 mm nylon cyclone. Samples are collected at a maximum flow rate of 1.7 liters/minute (respirable fraction) or 2.0 liters/minute (total dust) until a maximum collection volume of 816 liters (respirable fraction) or 960 liters (total dust) is reached. Analysis is conducted by gravimetric methods. This method (for nuisance dusts) is described in the OSHA Computerized Information System [OSHA 1994] and is fully validated. NIOSH has published a similar method (Method No. 0500) for the sampling and analysis of nuisance dusts [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If zinc oxide contacts the skin, workers should flush the affected areas with water, followed by washing with soap and water.

Clothing contaminated with zinc oxide should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of zinc oxide.

A worker who handles zinc oxide should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, using toilet facilities, applying cosmetics, or taking medication.

Workers should not eat, drink, use tobacco products, apply cosmetics, or take medication in areas where zinc oxide or a solution containing zinc oxide is handled, processed, or stored.

STORAGE

Zinc oxide should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of zinc oxide should be protected from physical damage and should be stored separately from chlorinated rubber, linseed oil, magnesium, hydrogen fluoride, aluminum + hexachloroethane, zinc chloride or phosphoric acid, and water.

SPILLS AND LEAKS

In the event of a spill or leak involving zinc oxide, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Collect the spilled material in the most safe and convenient manner possible and place it into a sealed container for disposal.

SPECIAL REQUIREMENTS

U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Zinc oxide is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III) in 42 USC 11022.

* Reportable quantity requirements for hazardous releases

A hazardous substance release is defined by EPA as any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of contaminated containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required to notify the proper Federal, State, and local authorities [40 CFR 355.40].

Employers are not required by the emergency release notification provisions in 40 CFR Part 355.40 to notify the National Response Center of an accidental release of zinc oxide; there is no reportable quantity for this substance.

* Community right-to-know requirements

Employers are not required by EPA in 40 CFR Part 372.30 to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of zinc oxide emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Although zinc oxide is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of zinc oxide exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergencies. Workers should only use respirators that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

PERSONAL PROTECTIVE EQUIPMENT

Workers should use appropriate personal protective clothing and equipment that must be carefully selected, used, and maintained to be effective in preventing skin contact with zinc oxide. The selection of the appropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to zinc oxide. There are no published reports on the resistance of various materials to permeation by zinc oxide.

To evaluate the use of PPE materials with zinc oxide, users should consult the best available performance data and manufacturers' recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components.

Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve zinc oxide.

Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, caustic, or other toxic substance may be splashed into the eyes.

In addition to the possible need for wearing protective outer apparel (e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk.

Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness.

Protective clothing may interfere with the body's heat dissipation, especially during hot weather or during work in hot or poorly ventilated work environments.

ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

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NIOSH [1991]. Registry of toxic effects of chemical substances: Zinc oxide. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

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NIOSH [1994a]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-116.

NIOSH [1994b]. NIOSH manual of analytical methods. 4th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113.

NJDH [1986]. Hazardous substance fact sheet: Zinc oxide. Trenton, NJ: New Jersey Department of Health.

NLM [1992]. Hazardous substances data bank: Zinc oxide. Bethesda, MD: National Library of Medicine.

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