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.[1,2]

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.[3] Exposure to radioisotopes is addressed under the CAREX carcinogen profile for Ionizing Radiation.

Our Occupational Approach page outlines the general approach used to calculate prevalence and exposure level estimates for workplace exposures.

Data Sources

Data used in developing the occupational estimates for cobalt were collected from several sources:

1. The Canadian Workplace Exposure Database (CWED) contains over 2,900 measurements for cobalt exposure. These measurements were collected during the years 1981 to 2004 in Ontario and British Columbia workplaces.
2. Canadian and US scientific peer reviewed publications that addressed cobalt exposure in Canada and the United States.
3. Grey literature including technical reports from governments and international bodies.

Prevalence Estimate Method

CAREX defines exposure to cobalt as inhalation exposure to cobalt and its compounds (including cobalt metal with tungsten carbide and soluble cobalt salts) at work at levels significantly exceeding those encountered in non-occupational settings. Cobalt radioisotopes are not considered here but exposure to radioisotopes is addressed under the CAREX carcinogen profile for Ionizing Radiation.

To determine the number of workers potentially exposed to cobalt at work, CAREX occupational exposure experts used methods previously established in other peer-reviewed CAREX projects in Europe. A series of steps were taken to assign exposure proportions to occupations and industries at risk of exposure to cobalt.

1. Occupations and industries at risk of possible exposure to cobalt were identified using any combination of data sources described above.
2. The total number of workers in each identified occupation and industry intersection was obtained from Statistics Canada 2016 census data.
3. A percentage of workers exposed was assigned to that occupation and industry intersection. Percentages were determined by consultation with existing evidence in the data sources, previously established methods from the Europe CAREX estimates and the expert judgement of CAREX occupational hygienists.
4. The number of workers in the identified group is multiplied by the assigned percentage to calculate the prevalence estimate of workers exposed to cobalt.

Exposure Level Method

CAREX uses available workplace exposure measurements in the CWED to create exposure level categories by industry and occupation. For cobalt and its compounds, these categories are:

Category 1: Low Exposure

A group of workers (people in the same job category and industry) is put in this exposure category for one of two reasons:

1. The are no valid measurements, but a hygienist identified this group as typically exposed during literature and other reviews;
2. There are valid exposure measurements in the CWED and a hygienist review determined that exposure is plausible; AND EITHER:
   1. There are less than 10 samples available in the CWED, OR
   2. There are ≥10 measurements available but they do not meet the criteria for Moderate Exposure.

Category 2: Moderate Exposure

A group of workers is put in this exposure category if:

1. There are at least 25 individual samples in the CWED, AND
2. 20% or more samples have a value higher than 0.01 mg/m³ (which is half the current occupational exposure limit for cobalt compounds).

OR

1. There are at least 10, but less than 25, individual samples in the CWED, AND
2. 20% or more samples have a value higher than 0.02 mg/m³ (which is the current occupational exposure limit for cobalt compounds).

Category 3: High Exposure

A group of workers is put in this exposure category if:

1. There are at least 25 individual samples in the CWED, AND
2. 20% or more samples have a value higher than 0.02 mg/m³ (which is the current occupational exposure limit for cobalt compounds).