Cobalt

2021-04-02

Cobalt is a chemical element with symbol Co and atomic number 27. [1] It is a hard ferromagnetic, silver-white, lustrous, brittle element. It is a member of group VIII of the periodic table. Like iron, it can be magnetised. Cobalt is similar to iron and nickel in its physical properties. The element is active chemically, forming many compounds. Cobalt is stable in air and unaffected by water, but is slowly attacked by dilute acids. [2] It will burn when exposed to heat and the fumes may be hazardous. Small amounts of cobalt are found in most rocks, soil, water, plants, and animals. It is a component of vitamin B-12, which is required for good health. [3]

Uses [2,3]

Cobalt is used in many alloys (superalloys for parts in gas turbine aircraft engines, corrosion resistant alloys, high-speed steels, cemented carbides), in magnets and magnetic recording media, as catalysts for the petroleum and chemical industries, as drying agents for paints and inks. Cobalt blue is an important part of artists’ palette and is used by craft workers in porcelain, pottery, stained glass, tiles and enamel jewellery. The radioactive isotope, cobalt-60, is used in medical treatment and also to irradiate food, in order to preserve the food and protect the consumer. Cobalt is also used to make artificial body parts such as hip and knee joints.

Sources of Emission & Routes of Exposure

Sources of Emission [3]

  • Industry sources: Cobalt is mainly emitted from sources where it is used in the production of steel and other alloys. It may be emitted to air, land or water from these sources. Automotive repair shops may be significant emitters (to air) of cobalt. It will also be emitted to air, land and water during the mining or refining of nickel, copper, silver, lead and iron.
  • Diffuse sources: Cobalt may be emitted to air, land or water from the manufacture, use or disposal of paints and varnishes. It may also be emitted to air, land or water from the manufacture, use or disposal of ceramic, inks, and enamels.
  • Natural sources: Cobalt is found in soil, dust, seawater, volcanic emissions, and smoke from forest and bush fires.
  • Transport sources: Small amounts of cobalt have been found in motor vehicle exhaust.
  • Consumer products: Consumer products containing cobalt and its compounds include: vitamin B-12, animal feeds and fertilisers, paints, varnish, enamels and ceramics. It is in metals used at high temperatures (e.g. some car parts).

Routes of Exposure [4,5]

  • Exposure to low levels of cobalt can occur by breathing air, eating food, or drinking water. Consumption of food and drinking water are the largest sources of exposure to cobalt for the general population.
  • Working in industries that make or use cutting or grinding tools; mine, smelt, refine, or process cobalt metal or ores; or that produce cobalt alloys or use cobalt.
  • The general population is rarely exposed to radioactive cobalt unless a person is undergoing radiation therapy. However, workers at nuclear facilities, irradiation facilities, or nuclear waste storage sites may be exposed to radiation from these sources.
  • Exposure to cobalt metal fume and dust can occur through inhalation, ingestion, and eye or skin contact.

Health Effects [6]

Acute Effects

Acute exposure to high levels of cobalt by inhalation in humans and animals results in respiratory effects, such as a significant decrease in ventilatory function, congestion, oedema, and haemorrhage of the lung. Acute animal tests in rats have shown cobalt to have extreme toxicity from inhalation exposure, and moderate to high toxicity from oral exposure.

Chronic Effects

Cobalt is an essential element in humans and animals as a constituent of vitamin B12. Cobalt has also been used as a treatment for anaemia, because it stimulates red blood cell production. Chronic exposure to cobalt by inhalation in humans results in effects on the respiratory system, such as respiratory irritation, wheezing, asthma, decreased lung function, pneumonia, and fibrosis. Other effects noted in humans from inhalation exposure to cobalt include cardiac effects, such as functional effects on the ventricles and enlargement of the heart, congestion of the liver, kidneys, and conjunctiva, and immunological effects that include cobalt sensitisation, which can precipitate an asthmatic attack in sensitised individuals. Cardiovascular effects (cardiomyopathy) were observed in people who consumed large amounts of beer over several years time containing cobalt sulphate as a foam stabiliser. The effects were characterised by cardiogenic shock, sinus tachycardia, left ventricular failure, and enlarged hearts. Gastrointestinal effects (nausea, vomiting, and diarrhoea), effects on the blood, liver injury, and allergic dermatitis have also been reported in humans from oral exposure to cobalt. Animal studies have reported respiratory, cardiovascular, and central nervous system (CNS) effects, decreased body weight, necrosis of the thymus, and effects on the blood, liver, and kidneys from inhalation exposure to cobalt. EPA has not established a Reference Concentration (RfC) or a Reference Dose (RfD) for cobalt.

Reproductive/Developmental Effects

No information is available on the reproductive or developmental effects of cobalt in humans via inhalation exposure. In one oral study, no developmental effects on human foetuses were observed following treatment of pregnant women with cobalt chloride. Animal studies, via inhalation exposure, have reported testicular atrophy, a decrease in sperm motility, and a significant increase in the length of the oestrus cycle, while oral studies have reported stunted growth and decreased survival of newborn pups. These effects on the offspring occurred at levels that also caused maternal toxicity.

Cancer Risk

Limited data are available on the carcinogenic effects of cobalt. In one study on workers that refined and processed cobalt and sodium, an increase in deaths due to lung cancer was found for workers exposed only to cobalt. However, when this study was controlled for date of birth, age at death, and smoking habits, the difference in deaths due to lung cancer was found to not be statistically significant. In another study assessing the correlation between cancer deaths and trace metals in water supplies in the United States, no correlation was found between cancer mortality and the level of cobalt in the water. In a study by the National Toxicology Program (NTP), cobalt sulphate heptahydrate exposure via inhalation resulted in increased incidences of alveolar/bronchiolar tumours in rats and mice. In an animal study, inhalation of cobalt over a lifetime did not increase the incidence of tumours in hamsters. Cobalt, via direct injection under the muscles or skin, has been reported to cause tumours at the injection site in animals. EPA has not classified cobalt for carcinogenicity.

Safety [5,7]

First Aid Measures

  • Eye Contact: Check for and remove any contact lenses. Do not use an eye ointment. Seek medical attention.
  • Skin Contact: After contact with skin, wash immediately with plenty of water. Gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. Cover the irritated skin with an emollient. If irritation persists, seek medical attention. Wash contaminated clothing before reusing.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek medical attention.
  • Inhalation: Allow the victim to rest in a well-ventilated area. Seek immediate medical attention.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention.
  • Ingestion: DO NOT induce vomiting. Loosen tight clothing such as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention.

Exposure Controls & Personal Protection

Engineering Controls

Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

Personal Protection

The following personal protective equipment is recommended when handling cobalt:

  • Splash goggles
  • Lab coat
  • Dust respirator (be sure to use an approved/certified respirator or equivalent)
  • Gloves

Personal Protection in Case of a Large Spill:

  • Splash goggles
  • Full suit
  • Dust respirator
  • Boots
  • Gloves
  • A self-contained breathing apparatus should be used to avoid inhalation of the product.
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Regulation [3,5,6]

  • United States

  • OSHA: he 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 metre (mg/m3) of air as an 8-hour time-weighted average (TWA) concentration [29 CFR 1910.1000, Table Z-1].

  • NIOSH: 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/m3 as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].
  • ACGIH: 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/m3 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].
  • The California Environmental Protection Agency (CalEPA) has established a chronic reference exposure level of 0.000005 milligrams per cubic metre (mg/m3) for cobalt based on respiratory effects in rats and mice.
  • ATSDR has established an intermediate inhalation minimal risk level (MRL) of 0.00003 mg/m3 based on respiratory effects in rats.

Australia

Safe Work Australia:

  • For cobalt, an eight-hour TWA exposure limit of 0.05 mg/m3 has been set
  • For cobalt carbonyl (as cobalt), an eight-hour TWA exposure limit of 0.1 mg/m3 has been set
  • For cobalt hydrocarbonyl (as cobalt), an eight-hour TWA exposure limit of 0.1 mg/m3 has been set

References

http://en.wikipedia.org/wiki/Cobalt

http://www.lenntech.com/periodic/elements/co.htm

http://www.npi.gov.au/substances/cobalt/index.html

http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=372&tid=64

http://www.osha.gov/SLTC/healthguidelines/cobaltmetaldustandfume/recognition.html

http://www.epa.gov/ttnatw01/hlthef/cobalt.html

http://www.sciencelab.com/msds.php?msdsId=9923518