Cobalt Occupational Exposures

Cobalt Occupational Exposures

Overview

Dusts and fumes containing cobalt may enter the respiratory tract, making inhalation the most important route of occupational exposure.[1]

CAREX Canada estimates that approximately 25,000 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.

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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.

Prevalence Estimate

Results show that approximately 25,000 Canadians are exposed to cobalt in their workplaces; 85% of these workers are male.

The main industrial groups exposed are metal ore mining, sawmills and wood preservation (where sawfilers are exposed during grinding), and offices of dentists (where cobalt is used in some dental prosthetics).

The largest occupational groups exposed include welders and related machine operators (4,800 workers exposed), dental technologists, technicians and laboratory assistants (2,700 workers exposed), and machinists and machining and tooling inspectors (2,000 workers exposed), and machining tool operators (1,300 workers exposed).

The number of workers exposed to cobalt decreased by approximately 7,500 workers from 2006 to 2016 (a 23% decrease). This was driven by a decrease in the total number of workers in the sawmills and wood preservation, medical equipment, and mining industries.

Workers exposed to cobalt by industry in 2016

Workers exposed to cobalt by region in 2016

Click the second tab to view total number of workers exposed.

* = < 50 workers

Level of Exposure

In total, approximately 25,000 Canadians are exposed to cobalt and its compounds in their workplaces. The majority of workers exposed to cobalt are in the low exposure category.

Workers exposed to cobalt by exposure level in 2016

Level of exposure by industry

Identifying industries with either 1) workers exposed to high levels of cobalt or 2) a larger number of workers exposed to cobalt is important in guiding cancer prevention efforts to prioritize exposed groups and target resources most effectively.

The table below shows the number of workers exposed by industry group and level of exposure to cobalt. These results highlight industries with the most number of workers, as well as industries with the highest levels of exposure.  For example, in ambulatory health care services, all of the exposed workers are in the low category. However, in fabricated metal product manufacturing and machinery manufacturing, many of the workers are in the moderate and high categories of exposure. Depending on the goals of a prevention campaign, exposure reduction in the large industrial group might be a useful strategy, or reducing exposure to those at highest risk of exposure could be seen as a priority.

Workers exposed to cobalt by exposure level and industry in 2016


*Numbers may not add up due to rounding

 

Methods and Data

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).
Sources

1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for cobalt (2004) (PDF)
2. Teschke, Kennedy & Chessor. Hard Metal Mists and Myths (1999)
3. Health Canada.Radiation Protection Bureau (2007)

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