Disclaimer: These guidelines were developed under contract using generally accepted secondary sources. The protocol used by the contractor for surveying these data sources was developed by the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the Department of Energy (DOE). The information contained in these guidelines is intended for reference purposes only. None of the agencies have conducted a comprehensive check of the information and data contained in these sources. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The secondary sources used for supplements 111 and 1V were published before 1992 and 1993, respectively, and for the remainder of the guidelines the secondary sources used were published before September 1996. This information may be superseded by new developments in the field of industrial hygiene. Therefore readers are advised to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR COBALT METAL, DUST, AND FUME (As Co)

INTRODUCTION

This guideline summarizes pertinent information about cobalt metal, dust, and fume 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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.

APPLICABILITY

The general guidelines contained in this document apply to the metal, cobalt, and the dust and fumes of several cobalt compounds, such as cobaltous oxide, cobaltic oxide, and cobaltic-cobaltous oxide. When specific data are available, this guideline identifies the form of cobalt (metal, dust, or fume) or the compound to which the information applies.

SUBSTANCE IDENTIFICATION

* Formula

Co; CoO; Co(2)O(2); CO(2)O(4)

* Structure

Structures vary depending on specific compound.

* Synonyms

Synonyms vary depending on specific compound.

* Identifiers

1. CAS No.: 7440-48-4 (metal)

2. RTECS No.: GF8750000 (metal)

3. Specific DOT UN: None.

4. Specific DOT label: None.

* Appearance and odor

Cobalt is a silvery, bluish-white, odorless, and magnetic metal. The fume and dust of cobalt metal is odorless and black. The appearance and odor of cobalt compounds and their dusts and fumes vary with the compound.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Atomic weight: 58.9 (metal)

2. Boiling point (at 760 mm Hg): 3100 to 3200 degrees C (5612 to 5792 degrees F) (metal)

3. Specific gravity (water = 1): 8.92 (metal) at 20 degrees C (68 degrees F)

4. Vapor density: Not applicable.

5. Melting point: 1493 degrees C (2719.4 degrees F) (metal)

6. Vapor pressure at 20 degrees C (68 degrees F): Data not available.

7. Solubility: Insoluble in water; soluble in nitric acid and other acids.

8. Evaporation rate (butyl acetate = 1): Not applicable.

* Reactivity

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Contact between cobalt metal in powdered form and fused ammonium nitrate, hydrozinium nitrate, or strong oxidizing agents should be avoided. Ignites on contact with bromide pentafluoride. Powdered cobalt ignites spontaneously in air.

3. Hazardous decomposition products: None reported.

4. Special precautions: None reported.

* Flammability

The National Fire Protection Association has not assigned a flammability rating to cobalt metal, dust, and fume; however, powdered cobalt (pyrophoric cobalt) is combustible and burns brilliantly in air at room temperature. Dusts of cobalt metal or cobalt compounds may form explosive mixtures in air.

1. Flash point: Data not available.

2. Autoignition temperature: Data not available.

3. Flammable limits in air: Data not available.

4. Extinguishant: Do not use water; dry sand, dry dolomite, dry graphite powder, or sodium chloride have been recommended for fighting fires involving cobalt.

Fires involving cobalt metal, dust, and fume 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 cobalt metal, dust, and fume.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for cobalt metal, dust, and fume (as Co) is 0.1 milligram per cubic meter (mg/m(3)) of air 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 a recommended exposure limit (REL) for cobalt metal, dust, and fume of 0.05 mg/m(3) as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned cobalt, elemental, and inorganic compounds (as Co) a threshold limit value (TLV) of 0.02 mg/m(3) as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH also lists these substances as animal carcinogens (A3 substances) [ACGIH 1994, p. 17].

* Rationale for Limits

The NIOSH limit is based on the risk of dermatitis, and the potential for pulmonary fibrosis [NIOSH 1992].

The ACGIH limit is based on the risk of pulmonary effects.

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to cobalt metal fume and dust can occur through inhalation, ingestion, and eye or skin contact [Sittig 1991].

* Summary of toxicology

1. Effects on Animals: Cobalt metal, dust, and fume are pulmonary toxins and respiratory and skin sensitizers. The oral LD(50) in rats is 6,171 mg/kg. Rats injected intramuscularly with the powder of cobalt metal or cobalt oxide developed malignancies of the skeletal muscle [Hathaway et al. 1991]. Oral exposure of rats to 1,500 mg cobalt metal was lethal to all animals. All rats fed 30 mg cobalt metal per day for 1 month also died [Clayton and Clayton 1982]. Guinea pigs developed obstructive inflammation of the lung, pneumonitis, pleural effusions, and inflammation of the pericardial sac following intratracheal injection of cobalt metal or a mixture of 25 percent cobalt metal and 75 percent tungsten carbide. These pathological changes were often rapidly fatal [Clayton and Clayton 1982]. Miniature swine exposed daily by inhalation to 0.1 mg/m(3) of a cobalt metal dust developed pulmonary disease within three months [ACGIH 1991]. Chronic exposures to 20 mg/m(3) of a cobalt metal blend produced focal fibrosis and granulomas of the lungs and hyperplastic changes in the mucosa lining the smaller airways [Clayton and Clayton 1982]. High doses of cobalt also caused foci of cell death and diffuse degenerative changes in heart muscle [Parmeggiani 1983]. Cobalt metal introduced into the eyes of rabbits resulted in irritation and the development of abscesses that involved intraocular structures [Grant 1986].

2. Effects on Humans: Inhalation of cobalt metal fume and dust may cause interstitial fibrosis, interstitial pneumonitis, myocardial and thyroid disorders, and sensitization of the respiratory tract and skin [Hathaway et al. 1991; Parmeggiani 1983]. Chronic cobalt poisoning may also produce polycythemia and hyperplasia of the bone marrow [NLM 1995]. Among the 12 workers engaged in the manufacture or grinding of tungsten carbide tools (cobalt is used as a binder for tungsten carbide crystals), who developed interstitial lung disease, there were eight fatalities [Hathaway et al. 1991]. A 16.6 percent incidence of skin sensitivity to cobalt was found in patch testing of cement workers in Finland. A review of 14 other reports on European cement workers showed a 25 percent average incidence of sensitization [Clayton and Clayton 1982]. Acute forms of cardiomyopathy, hypothyroidism, and thyroid hyperplasia were seen in Canada after cobalt was added to beer to stabilize the foam. Myocardial disorders have also been observed in cobalt production workers [NLM 1995].

* Signs and symptoms of exposure

1. Acute exposure: Acute exposure to cobalt metal, dust, and fume is characterized by irritation of the eyes and, to a lesser extent, irritation of the skin [Sittig 1991]. In sensitized individuals, exposure causes an asthma-like attack, with wheezing, bronchospasm, and dyspnea [Hathaway et al. 1991]. Ingestion of cobalt may cause nausea, vomiting, diarrhea, and a sensation of hotness [Sittig 1991; Sax and Lewis 1989].

2. Chronic exposure: Chronic exposure to cobalt metal, dust, or fume may cause respiratory or dermatologic signs and symptoms. Following skin sensitization, contact with cobalt causes eruptions of dermatitis in creases and on frictional surfaces of the arms, legs, and neck [Genium 1988]. Following sensitization of the respiratory system, cobalt exposure causes an obstructive lung disease with wheezing, cough, and shortness of breath [Parmeggiani 1983; NJDH 1985]. Chronic respiratory exposure results in reduced lung function, increased fibrotic changes on chest X-ray, production of scanty mucoid sputum, and shortness of breath. Chronic cobalt poisoning may cause polycythemia, hyperplasia of the bone marrow and thyroid gland, pericardial effusion, and damage to the alpha cells of the pancreas [NLM 1995].

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 cobalt metal, dust, and fume and lead to worker exposures to this substance:

* The manufacture and transportation of cobalt metal, dust, and fume

* Liberated during use as a binder in manufacture of cemented carbide items, during the grinding of cemented carbide and steel tools, and during the preparation of alloys and cobalt salts

* Liberated during synthesis of cobalt compounds for use in the electroplating, ceramics, glass, photography, enamels, and pigment industries; used as driers and catalysts

* Liberated during manufacture of metal items from cutting tool and tool steels, from hardfacing alloys, from magnetic alloys, and from super- and high-temperature alloys; during manufacture of items containing low-expansion alloys and constant-modulus alloys; during manufacture of metal-to-glass seals in electric lamps, vacuum tubes, and X-ray tubes

* Liberated during manufacture of permanent and soft magnets, and dental prosthetic and osteosynthetic items; during asbestos fiber processing

* Used in jet engines, cobalt and hydrogen bombs, nuclear technology, experimental medicine, cancer research, and cancer treatment

* Used as trace element in fertilizers, as an additive in cattle feed, and in the manufacture of lamp filaments

Methods that are effective in controlling worker exposures to cobalt metal, dust, and fume, 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.

MEDICAL SURVEILLANCE

OSHA is currently developing requirements for medical surveillance. When these requirements are promulgated, readers should refer to them for additional information and to determine whether employers whose employees are exposed to cobalt metal, dust, and fume are required to implement medical surveillance procedures.

* Medical Screening

Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical surveillance program is intended to supplement, not replace, such measures. To detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the term of employment, and (3) at the time of job transfer or termination.

* Preplacement medical evaluation

Before a worker is placed in a job with a potential for exposure to cobalt metal, dust, and fume, a licensed health care professional should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the respiratory system and skin. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American Thoracic Society.

A preplacement medical evaluation is recommended to assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to cobalt metal, dust, and fume at or below the prescribed exposure limit. The health care professional should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the respiratory system or skin.

* Periodic medical evaluations

Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to cobalt metal, dust, and fume exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of cobalt metal, dust, and fume on the respiratory system or skin. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.

* Termination medical evaluations

The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population. Because occupational exposure to cobalt metal, dust, and fume may cause diseases with prolonged latent periods, the need for medical surveillance may extend well beyond the termination of employment.

* Biological monitoring

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. Cobalt can be detected in the urine of exposed workers using atomic absorption spectroscopy. End-of-shift urine cobalt concentrations were found to correlate well with worker's exposure in a hard metal manufacturing plant. Urinary cobalt concentrations ranged from 1 to 35 microgram per liter of urine for airborne cobalt levels of 2.5 to 105 micrograms per cubic meter.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne cobalt metal, dust, or fume (as Co) is made using a mixed cellulose ester filter (MCEF), 0.8 microns. Samples are collected at a maximum flow rate of 2.0 liters/minute until a minimum collection volume of 480 liters or a maximum collection volume of 960 liters is reached. Analysis is conducted by atomic absorption spectroscopy (AAS). This method (OSHA ID-121) is fully validated and is described in the OSHA Computerized Information System [OSHA 1994]. NIOSH has also published a similar method (Method No. 7027) that can be used to determine a worker's exposure to cobalt metal, dust, or fume [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If cobalt metal or dust contacts the skin, workers should immediately wash the affected areas with soap and water.

Clothing contaminated with cobalt metal or dust 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 cobalt metal, dust, and fume, particularly its potential for causing eye and skin irritation.

A worker who handles cobalt metal or dust 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 cobalt metal, dust, or fume or a solution containing cobalt metal or dust is handled, processed, or stored.

STORAGE

Cobalt metal dust (powdered metal) 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 cobalt metal dust should be protected from physical damage and ignition sources, and should be stored separately from strong oxidizers.

SPILLS AND LEAKS

In the event of a spill or leak involving cobalt metal or dust, 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. Notify safety personnel.

2. Remove all sources of heat and ignition.

3. Ventilate potentially explosive atmospheres.

4. Do not touch the spilled material.

5. For small dry spills, use a vacuum or a wet mop to clean up spill. If these are not available, use a clean shovel and place the material into a clean, dry container; cover and remove the container from the spill area.

6. For large spills, wet down with water and build dikes far ahead of the spill to contain the cobalt metal or dust for later reclamation or 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

Cobalt metal, dust, and fume 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 cobalt metal, dust, and fume; there is no reportable quantity for this substance.

* Community right-to-know requirements

Employers who own or operate facilities in SIC codes 20 to 39 that employ 10 or more workers and that manufacture 25,000 pounds or more of cobalt metal, dust, and fume per calendar year or otherwise use 10,000 pounds or more of cobalt metal, dust, and fume per calendar year are required by EPA [40 CFR Part 372.30] to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of cobalt metal, dust, and fume 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 cobalt metal, dust, and fume 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 cobalt metal, dust, and fume 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 cobalt metal, dust, and fume. 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 cobalt metal, dust, and fume. There are no published reports on the resistance of various materials to permeation by cobalt metal, dust, and fume.

To evaluate the use of PPE materials with cobalt metal, dust, and fume, 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 cobalt metal, dust, and fume.

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.

REFERENCES

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.

ATS [1987]. Standardization of spirometry -- 1987 update. American Thoracic Society. Am Rev Respir Dis 136:1285-1296.

Baselt RC [1988]. Biological monitoring methods for industrial chemicals. 2nd ed. Davis, CA: Biomedical Publications.

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Genium [1988]. Material safety data sheet No. 82. Schenectady, NY: Genium Publishing Corporation.

Grant WM [1986]. Toxicology of the eye. 3rd ed. Springfield, IL: Charles C Thomas.

Hathaway GJ, Proctor NH, Hughes JP, and Fischman ML [1991]. Proctor and Hughes' chemical hazards of the workplace. 3rd ed. New York, NY: Van Nostrand Reinhold.

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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.

NIOSH [1995]. Registry of toxic effects of chemical substances: Cobalt. 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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