CAREX Canada

Full Profile

CAS No. 7440-48-4

Photo Source: Wikimedia Commons ^[1]

IARC Monograph Vol. 52, 1991

Cobalt and Cobalt Compounds (Group 2B)

IARC Monograph Vol. 86, 2006

Cobalt Metal with Tungsten Carbide (Group 2A)

Cobalt Sulfate and Other Soluble Cobalt (II) Salts (Group 2B)

General Information

Cobalt is a naturally-occurring, silvery-grey magnetic metal with properties similar to those of iron and nickel. Cobalt is found in small amounts in most rocks, soil, water, and organisms.^[2] It is usually combined with oxygen, sulphur, or arsenic.^[2] Vitamin B12, a cobalt compound, is an important dietary nutrient.^[3] Cobalt has several radioisotopes, two of which are commercially important (⁶⁰Co, ⁵⁷Co).^[2] There are numerous other synonyms and product names for cobalt; see IARC or HSDB for more information.^[4-6,26]

Cobalt and its compounds were classified by IARC in 1991 as Group 2B, possibly carcinogenic to humans, due to inadequate evidence in humans linking exposure and lung cancer, but limited or sufficient evidence in animals for some specific cobalt compounds.^[4] In 2006, IARC evaluated the exposure circumstance of cobalt metal with tungsten carbide in powders, hard metals or sintered carbides as Group 2A, probably carcinogenic to humans.^[6] Although recent epidemiological studies of hard metal workers in France and Sweden have reported increased lung cancer rates in workers exposed to cobalt with tungsten carbide, more conclusive epidemiological evidence or strong mechanistic evidence are required for a Group 1 designation.^[6]

The 2006 monograph also included an evaluation of cobalt metal without tungsten carbide as well as cobalt sulfate and other soluble cobalt (II) salts, which remain in Group 2B.^[6] Increased cancer risk has been reported from working with cobalt compounds without tungsten carbide, however these studies were limited by small numbers and lack of control for confounding variables.^[6]

Respiratory effects of chronic occupational exposure are well documented. Cobalt is likely the primary contributor to the effects of hard metal welding which range from irritation, decreased pulmonary function and asthma to hard metal lung disease involving pneumonia and fibrosis.^[2] Cardiovascular effects have also been reported from inhalation exposures.^[2] Cobalt exposure can result in skin sensitization and allergic dermatitis.^[2]

Cobalt and its compounds have been ranked by CAREX Canada as a Group A (immediate high priority) for occupational settings and as a Group B (possible high priority) for environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Canadian Jurisdictions	OEL (mg/m³)
Canada Labour Code	0.02
MB, NL, PEI, NB, NS	0.02
BC, AB, PQ	0.02
SK	0.02 0.06 [stel]
ON	0.02 [metal dust, fume]
YT	0.05 0.15 [stel]
NT, NU	0.1 0.3 [stel]
Other Jurisdiction	OEL (mg/m³)
ACGIH 2011 TLV	0.02

mg/m³ = milligrams per cubic meters

stel = short term exposure limit (15 min. maximum)

Canadian Environmental Guidelines

Cobalt and its inorganic compounds were not included in the Canadian government environmental guidelines reviewed.^[7-10]

Canadian Agencies/Organizations

Agency	Designation/Position	Year (ref)
Health Canada	DSL – high priority substance with the greatest potential for exposure	2006^[11]
Challenge to Industry	Batch 10 For cobalt, cobalt chloride, cobalt sulfate	2011^[13]

Cobalt and its compounds were not included in other Canadian government chemical listings reviewed.^[12]

Main Uses

The Cobalt Development Institute (CDI) outlines the use of cobalt^[16] 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, agriculture, and medicine. For further uses of cobalt, please see the CDI’s listing of properties and main uses (PDF).

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.^[15]

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 used in medical and scientific research.^[2]

Canadian Production and Trade

Canada produced approximately 10% of the world’s refined cobalt in 2007 (5,650 of the 53,500 tonnes world total).^[16] MDS Nordion is a Canadian supplier of ⁶⁰Cobalt based in Ottawa; they also have several international facilities.^[18]

Canadian cobalt production is generally a by-product of nickel mining. As a result, data on cobalt production is not as complete as for nickel.^[17] Although reporting on nickel, Natural Resources Canada mentioned that cobalt was produced as a by-product from 4 mines in Canada in 2006: 2 in Ontario, 1 in Quebec, and 1 in Labrador.^[17] Cobalt was also mentioned as a product from three nickel refineries (in Ontario, Manitoba, and Alberta).^[17]

Production and Trade

Activity	Quantity	Year
Canadian production	5,650 t of refined cobalt	2007^[16]
Export: Mainly to China	2196 t of ‘cobalt ores and concentrates’	2010^[19]
Export: Mainly to US	425 t of 'cobalt oxides'	2010^[19]
Import: Mainly from Japan, Belgium	63 t of 'cobalt oxides'	2010^[19]

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Occupational Exposures

Inhalation is the most important route of occupational exposure. Dusts and fumes containing cobalt may enter the respiratory tract.^[2] The main occupations exposed include workers involved in metal mining, smelting and refining, production or use of cutting/grinding tools, cobalt dye painting and cobalt chemical production.^[2]

Other occupations, including those with potential dermal exposure, include diamond polishers, welders, dental technicians, glassware/porcelain workers, offset printers, goldsmiths and rockwool insulators.^[20]

Workers involved in production or handling of 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.^[21] Exposure to radioisotopes will be addressed under the CAREX carcinogen profile for Ionizing Radiation.

Environmental Exposures

The vast majority (99%) of the general population's cobalt intake is estimated to be from food.^[22] Cobalt in dietary sources comes from soil uptake by plants, and also from the presence of vitamin B12.^[2] Other sources include drinking water, vehicle exhaust and tobacco smoke.^[2]

Anthropogenic sources, which make up the majority of emissions, include the burning of fossil fuels, sewage sludge, phosphate fertilizers, mining and smelting of cobalt ores, processing of cobalt alloys and industries that use or process cobalt compounds.^[23]

Natural sources of cobalt released into the environment include wind-blown dust, seawater spray, volcanoes and forest fires ^[23]. The mean atmospheric cobalt levels at unpolluted sites are generally <1 to 2 ng/m³. Levels near industrial sources of cobalt may exceed 10 ng/m³.^[23]

Searches of environmental and consumer product databases yielded the following results on current potential for exposure to cobalt in Canada:

NPRI and US Household Products Database

NPRI 2009^[24]
Search term: 'cobalt and its compounds'
Category	Quantity	Industry
Released into Environment	7.4 t	Mining, battery companies, paint companies and refineries (97 companies)
Disposed of	3,849 t
Sent to off-site recycling	344 t