Arsenic Occupational Exposures


Inhalation and dermal contact are the most important routes of occupational exposure.[1] CAREX Canada estimates that approximately 25,000 Canadians are exposed to arsenic at work; about half are exposed due to the use of arsenic in CCA wood preservatives.


The industries with the highest number of exposed workers are foundation, structure, and building exterior contractors, as well as sawmills and wood preservation, and non-residential building construction. These workers are primarily exposed to arsenic through CCA treated wood. Workers are also exposed to arsenic in metal processing and manufacturing, oil and gas extraction, metal and ore mining, and water, sewage and other systems industries. Overall, larger numbers of exposed workers are employed in British Columbia and Quebec due to the large wood and wood product manufacturing industries in these provinces.

Prevalence Estimate

Results show that approximately 25,000 Canadians are currently exposed to arsenic at work. Of these, 90% are male.

The industry with the largest number of workers exposed is the foundation, structure and building exterior contractors, sawmills and wood preservation, building construction, and farms. Exposure in these groups primarily occurs through contact with arsenic-containing CCA wood preservatives. Workers may also be exposed to arsenic in the workplace in industries other than wood preservation. For example, exposure to arsenic occurs in the non-ferrous metal production and processing industry, as well as in iron and steel mills, where arsenic is produced as a by-product of the processing of other metals.

When exposure is examined by occupation, the largest groups of workers exposed to arsenic are construction trades helpers and labourers, carpenters, machinists and machining and tooling inspectors, and labourers in wood, pulp and paper processing.

Overall, larger numbers of exposed workers are employed in British Columbia and Quebec due to the large wood and wood product industries in these provinces.

Workers exposed to arsenic by industry

arsenic exposure in Canada

Workers exposed to arsenic by region

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

* = < 50 workers
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 arsenic were collected from several sources:

  1. The Canadian Workplace Exposure Database (CWED) contains over 700 measurements for arsenic 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 arsenic 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 arsenic as inhalation or dermal contact at work to levels above those encountered in the general environment (i.e. excluding exposure via ingestion of food or drinking water). In occupations involving wood preservation, exposure to arsenic includes direct contact with preservatives, as well as during the handling and processing of CCA-treated wood.

To determine the number of workers potentially exposed to arsenic 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 arsenic.

  1. Occupations and industries at risk of possible exposure to arsenic 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 arsenic.

1. National Toxicology Program (NTP). 14th report on carcinogens for Arsenic Compounds, Inorganic (2016) (PDF)

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