METALS – MULTIPLE CLASSIFICATIONS (IARC 2A, 2B)
Cobalt is a naturally-occurring, silvery-grey magnetic metal with properties similar to iron and nickel. Small amounts of cobalt are found in most rocks, soil, water, and organisms. It is usually combined with oxygen, sulphur, or arsenic. Vitamin B12, a cobalt-containing compound also referred to as cobalamin, is an important dietary nutrient. Cobalt has several radioisotopes, two of which are commercially important (60Co, 57Co). There are numerous other synonyms and product names for cobalt; see the Hazardous Substances Data Bank (HSDB) for more information.[3,4,5]
Cobalt and its compounds were classified by the International Agency for Research on Cancer (IARC) in 1991 as Group 2B, possibly carcinogenic to humans. This classification was based on inadequate evidence in humans linking exposure and lung cancer, but limited or sufficient evidence in animals for some specific cobalt compounds. In 2006, IARC classified cobalt metal with tungsten carbide in powders, hard metals, or sintered carbides as Group 2A, probably carcinogenic to humans. Epidemiological studies of hard metal workers in France and Sweden reported increased lung cancer rates in workers exposed to cobalt with tungsten carbide. However, more conclusive epidemiological evidence or strong mechanistic evidence are required to establish a causal link.
In 2022, IARC re-evaluated cobalt metal without tungsten carbide, as well as soluble cobalt (II) salts, which are now classified as Group 2A, possibly carcinogenic to humans, on the basis of sufficient evidence of cancer among experimental animal studies and strong mechanistic evidence in human cells. Cobalt (II) oxide and weapons-grade tungsten alloy were classified as Group 2B, possibly carcinogenic to humans, due to sufficient evidence of cancer in experimental animals. Cobalt (II,III) oxide, cobalt (II) sulfide, and other cobalt (II) compounds were classified as Group 3, not classifiable as to its carcinogenicity to humans.
Respiratory effects of chronic occupational exposure to cobalt are well documented. Cobalt is likely the primary contributor to health effects associated with hard metal welding. These range from irritation, decreased pulmonary function, and asthma to hard metal lung disease involving pneumonia and fibrosis. Cardiovascular effects are also reported from inhalation exposures. Cobalt exposure can result in skin sensitization and allergic dermatitis.
Regulations and Guidelines
|Canadian Jurisdictions||OEL (mg/m3)|
|Canada Labour Code||0.02|
|AB, BC, MB, NB, ON, PE||0.02|
|NL, NS||0.02 [i, dsen, rsen]|
|NT, NU, SK||0.02
|Other Jurisdiction||OEL (mg/m3)|
|ACGIH 2020 TLV||0.02 [i, dsen, rsen]|
mg/m3 = milligrams per cubic meters
i = inhalable fraction
dsen = dermal sensitization
rsen = respiratory sensitization
stel = short term exposure limit (15 min. maximum)
s = sensitizer
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian environmental guidelines
|Ontario Ambient Air Quality Criteria||24-hour: 0.1 µg/m3||2016|
|BC’s Source Drinking Water Quality Guidelines||1 µg/L||2020|
|BC’s Contaminated Sites Regulation, BC Reg 375/96||Sets soil standards for the protection of human health:
Agricultural, low and high density residential, and urban park sites: 25 μg/g
Commercial sites: 75 μg/g
Industrial sites: 2,000 μg/g
Drinking water: 1 µg/L
µg/m3 = micrograms per cubic meters
|National Classification System for Contaminated Sites||Rank: “Low hazard”||2008|
|Health Canada||DSL – high priority substance with the greatest potential for exposure||2006|
|CEPA||Batch 10 Challenge to Industry
For cobalt, cobalt chloride, cobalt sulfate
|PMRA list of formulants||List 4B: contains formulants, some of which may be toxic, for which there are sufficient data to reasonably conclude that the specific use pattern of the pest control product will not adversely affect public health and the environment.||2018|
|Environment Canada’s National Pollutant Release Inventory||NPRI Part (Threshold Category): 1B, Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 50 kg . Total of the pure element and the equivalent weight of the element contained in any compound, alloy or mixture.||2016|
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
Cobalt and its compounds were not included in other Canadian government guidelines, standards, or chemical listings reviewed.
The Cobalt Institute (CI) outlines the use of cobalt in: high-quality, corrosion-resistant metal alloys; in hard and soft magnetic alloys and materials; as a binding agent in cutting and drilling tools; and as a component in batteries, pigments, electronics, and medicine. Further uses of cobalt are outlined on the CI’s webpage.[30,31]
The distribution of cobalt use in the US in 2006 was as follows: 49% superalloys (mainly for aircraft gas turbine engines); 9% in cemented carbide; 18% other metallic applications; 24% chemical applications.
Two cobalt radioisotopes, 60Cobalt and 57Cobalt, have commercial uses. 60Cobalt is used in cancer treatment, sterilization of medical and consumer products, food irradiation, and non-destructive testing. 57Cobalt is also used in scientific research.
Canadian Production and Trade
There are several Cobalt mining and refinery operations currently operating in Canada. Vale produced 1,675 t of refined cobalt metal at its Port Colborne refinery in Ontario in 2017 as well as 1,231 t of refined cobalt at the Long Harbour, NL, refinery . Vale’s cobalt originated from company-owned nickel sulfide mines at Sudbury (Ontario), Thompson (Manitoba), Voisey’s Bay (Labrador), and abroad. Glencore reported that 800 t of the cobalt produced at its Nikkelverk refinery in Norway originated from concentrates produced from its mines in Sudbury and Raglan (Quebec). The Fort Saskatchewan refinery in Alberta, a joint venture of Sherritt and General Nickel Co. S.A., produced 3,601 t of cobalt as metal powder and briquettes in 2017.
In 2021, Canada was responsible for 2.5% of global cobalt mine production and was ranked as the sixth largest global cobalt mine producer.
Production and trade
|Import:||0 t of ‘cobalt ores and concentrates’||2021|
|Export:||0 t of ‘cobalt ores and concentrates’||2021|
|Import:||111 t of ”cobalt oxides and hydroxides||2021|
|Export:||0 t of ”cobalt oxides and hydroxides||2020|
t = tonne
Environmental Exposures Overview
The vast majority (99%) of the general population’s cobalt intake is estimated to be from food. Cobalt in dietary sources results from soil uptake by plants, and also from vitamin B12. Other sources include drinking water, vehicle exhaust, and tobacco
Anthropogenic sources make up the majority of emissions. These include fossil fuel burning, sewage sludge, phosphate fertilizers, mining and smelting of cobalt ores, processing of cobalt alloys, and industries that use or process cobalt compounds.
Natural sources of cobalt released into the environment include wind-blown dust, sea water spray, volcanoes, and forest fires. The mean atmospheric cobalt levels at unpolluted sites are generally <1 to 2 nanograms/m3 (ng/m3). Levels near industrial sources of cobalt may exceed 10 ng/m3.
Searches of Environment Canada’s National Pollutant Release Inventory (NPRI) and the US Consumer Product Information Database yielded the following results on current potential for exposure to cobalt in Canada:
NPRI and US Consumer Product Information Database
|Substance name: ‘Cobalt and its compounds’|
|Released into Environment||21 t||Mining,
water, sewage and other systems,
motor vehicle manufacturing
|Disposed of||5,809 t|
|Sent to off-site recycling||140 t|
t = tonne
|US Consumer Products 2015|
|Search Term||Quantity||Product Type|
|‘Cobalt and its compounds’||>60||Paints, glazes, and stains|
Occupational Exposures Overview
Dusts and fumes containing cobalt may enter the respiratory tract, making inhalation the most important route of occupational exposure.
CAREX Canada estimates that approximately 3,000 Canadians are exposed to cobalt in their workplace. The main industrial groups exposed are metal ore mining, sawmills and wood preservation, and offices of dentists. The largest occupational groups exposed include welders, dental technologists, technicians and laboratory assistants, and machinists and machining and tooling inspectors.
Additional occupations that may also be exposed to cobalt (including potential dermal exposure) are workers involved in: smelting and refining; cobalt dye painting and cobalt chemical production: diamond polishing; glassware/porcelain work; offset printing; goldsmithing; and rockwool insulating.[1,40]
Workers involved in producing or handling radioactive forms of cobalt, such as those at nuclear or irradiation facilities, medicine/research or waste storage sites, are regulated and monitored under Health Canada’s Radiation Protection Bureau. Exposure to radioisotopes is addressed under the CAREX carcinogen profile for Ionizing Radiation.
For more information, see the occupational exposure estimate for cobalt.
- US Environmental Protection Agency (EPA). Technology Transfer Network: Cobalt Compounds (2000) (PDF)
- Shedd, K.B. Mineral Commodity Summaries: Cobalt, Reston, VA, US Geological Survey, pp. 52-53 (2003) (PDF)
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