Chromium (Hexavalent) Occupational Exposures

Chromium (Hexavalent) Occupational Exposures

Overview

Inhalation and dermal contact are the most important routes of occupational exposure to hexavalent chromium (VI).[1] CAREX Canada’s estimates indicate that approximately 104,000 Canadians are occupationally exposed to chromium (VI). Most exposures (87%) occur in the low exposure category. However, many workers are exposed to moderate or high levels of chromium (VI) in fabricated metal products, machinery, and transportation equipment manufacturing.

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The industries with the largest numbers of exposed workers are automotive maintenance and repair, and printing and support activities. Other industries with larger numbers of workers exposed to chromium (VI) include saw mills and wood preservation, commercial and industrial machinery repair, and structural metal manufacturing.

In terms of occupation, the groups with the largest number of exposures to chromium (VI) are welders (who are exposed when welding stainless steel), machinists, and automotive technicians.

Prevalence Estimate

Results show that approximately 104,000 Canadians are occupationally exposed to chromium (VI); 92% of these workers are male. The largest industrial group exposed is the automotive repair and maintenance industry.

When examining exposure to chromium (VI) by occupation, the largest exposed group is welders (20,000 men and 850 women), where exposure to chromium (VI) occurs during the welding of stainless steel. There was significant variation in job title by gender; the largest groups for women are dental technologists and technicians, followed by printing machine and press operators (approximately 1,600 women exposed in each industry), while many more men exposed to chromium (VI) are welders, machinists, and automotive technicians.

Workers exposed to hexavalent chromium by industry

Workers exposed to hexavalent chromium by region

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

* = < 50 workers

Level of exposure

In total, approximately 104,000 Canadians are exposed to chromium (VI) in their workplaces. The majority of workers exposed to chromium (VI) are in the low exposure category. A substantial number of chromium (VI)-exposed workers are at risk for moderate exposure, while very few are in the high exposure category.

Level of Exposure by Industry

Identifying industries with either 1) workers exposed to high levels of chromium (VI) or 2) a larger number of workers exposed to chromium (VI) 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 chromium VI. These results highlight industries with the most number of workers, as well as industries with the highest levels of exposure. Data for those industries with at least 2,000 workers exposed is shown.

For example, in the repair and maintenance industry (which is the largest industrial group exposed to chromium (VI)), all of the exposed workers are in the low category. However, in transportation equipment manufacturing and fabricated metal product manufacturing, we see substantial groups of workers potentially exposed at moderate or high levels. 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.

*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 chromium (VI) were collected from several sources:

  1. The Canadian Workplace Exposure Database (CWED) contains 4,400 measurements for chromium (VI) 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 chromium (VI) 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 chromium (VI) as inhalation and/or dermal exposure to chromium at work above levels expected to be encountered in the general environment (i.e. from food or drinking water sources).

To determine the number of workers potentially exposed to chromium (VI) 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 chromium (VI).

  1. Occupations and industries at risk of possible exposure to chromium (VI) 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 2006 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 chromium (VI).

Exposure Level Method

Sources

1. National Toxicology Program (NTP). 14th Report on Carcinogens for Chromium Hexavalent Compounds (2016)

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