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Plant-Wide Hazards
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Health Hazards > Cobalt Dust
Stellite tipped saw blades generate a fine dust containing cobalt when sharpened. Cobalt is a silvery, bluish-white, odorless, and magnetic metal. The fume and dust of cobalt metal is odorless and black. Without proper ventilation, cobalt overexposures are possible. Cobalt also is combustible and burns brilliantly in air at room temperature. Dusts of cobalt metal or cobalt compounds may form explosive mixtures in air.
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Cobalt effects Top
  • 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. Chronic cobalt poisoning may also produce polycythemia and hyperplasia of the bone marrow. Among 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.

Exposure Limits Top
  • 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].

Signs and symptoms of exposure Top
  • 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. In sensitized individuals, exposure causes an asthma-like attack, with wheezing, bronchospasm, and dyspnea Ingestion of cobalt may cause nausea, vomiting, diarrhea, and a sensation of hotness.

  • 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. Following sensitization of the respiratory system, cobalt exposure causes an obstructive lung disease with wheezing, cough, and shortness of breath. 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.

Flammability Top
  • 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.

Controls Top
  • 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, and
    • Personal protective equipment.
  • 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. All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.

  • 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.

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