ZnO

(For Structure, see paper copy)

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

1. CAS No.: 1314-13-2

2. RTECS No.: ZH4810000

3. Specific DOT number: None

4. Specific DOT label: None

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

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.

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.

Zinc oxide is not combustible.

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

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.

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].

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].

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].

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].

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

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].

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.

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.

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

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.

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.

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.

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).

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].