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 (3,700 workers exposed), carpenters (2,900 workers exposed), machinists and machining and tooling inspectors (2,600 workers exposed), and labourers in wood, pulp and paper processing (1,400 workers exposed).
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.
Data Sources & Methods
Data used in developing the occupational estimates for arsenic were collected from several sources:
- 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.
- Canadian and US scientific peer reviewed publications that addressed arsenic exposure in Canada and the United States.
- 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.
- Occupations and industries at risk of possible exposure to arsenic were identified using any combination of data sources described above.
- The total number of workers in each identified occupation and industry intersection was obtained from Statistics Canada 2006 census data.
- 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.
- The number of workers in the identified group is multiplied by the assigned percentage to calculate the prevalence estimate of workers exposed to arsenic.