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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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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.
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.
Co; CoO; Co(2)O(2); CO(2)O(4)
Structures vary depending on specific compound.
Synonyms vary depending on specific compound.
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
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.
* 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
* Emergency medical procedures: [NIOSH to supply]
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:
Good sources of information about control methods are as follows:
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.
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:
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.
* 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.
ACGIH . Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
ACGIH . 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
ATS . Standardization of spirometry -- 1987 update. American Thoracic Society. Am Rev Respir Dis 36:1285-1296.
Baselt RC . Biological monitoring methods for industrial chemicals. 2nd ed. Davis, CA: Biomedical Publications.
CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.
Clayton G, Clayton F [1981-1982]. Patty's industrial hygiene and toxicology. 3rd rev. ed. New York, NY: John Wiley & Sons.
Genium . Material safety data sheet No. 82. Schenectady, NY: Genium Publishing Corporation.
Grant WM . Toxicology of the eye. 3rd ed. Springfield, IL: Charles C Thomas.
Hathaway GJ, Proctor NH, Hughes JP, and Fischman ML . Proctor and Hughes' chemical hazards of the workplace. 3rd ed. New York, NY: Van Nostrand Reinhold.
Lewis RJ, ed. . Hawley's condensed chemical dictionary. 12th ed. New York, NY: Van Nostrand Reinhold Company.
Lide DR . CRC handbook of chemistry and physics. 73rd ed. Boca Raton, FL: CRC Press, Inc.
Mickelsen RL, Hall RC . A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.
Mickelsen RL, Hall RC, Chern RT, Myers JR . Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.
NIOSH [1987a]. NIOSH guide to industrial respiratory protection. 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. 87-116.
NIOSH [1987b]. NIOSH respirator decision logic. 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. 87-108.
NIOSH . Recommendations for occupational safety and health: Compendium of policy documents and statements. 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. 92-100.
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 . 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.
NJDH . Hazardous substance fact sheet: Cobalt metal. Trenton, NJ: New Jersey Department of Health.
NLM . Hazardous substances data bank: Cobalt metal. Bethesda, MD: National Library of Medicine.
OSHA . Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.
Parmeggiani L . Encyclopedia of occupational health and safety. 3rd rev. ed. Geneva, Switzerland: International Labour Organisation.
Sax NI, Lewis RJ . Dangerous properties of industrial materials. 7th ed. New York, NY: Van Nostrand Reinhold Company.
Sittig M . Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications.
USC. United States code. Washington. DC: U.S. Government Printing Office.
Windholz M, ed. . Merck Index 10th ed. Rahway, NJ: Merck & Company.