Results show that 44,000 Canadians are exposed to bitumens in their workplaces; 95% of these workers are male. The largest exposed industrial groups are in the broad category of construction. Also important was the petroleum and coal products manufacturing industry (where bitumens are produced and processed into roofing and paving materials).
When exposure is examined by occupation, the largest exposed group is construction trades helpers and labourers (15,000 workers exposed), followed by roofers and shinglers (13,000 workers exposed), and heavy equipment operators (11,000 workers exposed).
Published February 2013
Data Sources & Methods
Data used in developing the occupational estimates for bitumens were collected from several sources:
- The Canadian Workplace Exposure Database (CWED) contains approximately 300 measurements for bitumens exposure. These measurements were collected during the years 1984 to 1993 in Ontario workplaces.
- Canadian and US scientific peer reviewed publications that addressed bitumens exposure in Canada and the United States.
- Grey literature including technical reports from governments and international bodies, as well as industry reports on the paving and roofing industries.
Prevalence Estimate Method
CAREX defines exposure to bitumens somewhat differently than for other agents. In the most recent IARC monograph focusing on bitumens, exposure was defined as it links to specific jobs and tasks; therefore we have taken a very similar approach in our updated exposure estimates. We define exposure to bitumens in the following ways:
- Working with oxidized bitumens and their emissions during roofing;
- Working with straight-run bitumens and their emissions during road paving;
- Production of roofing and paving materials.
IARC does not include the production of roofing and paving materials, but this exposure scenario is mentioned often in the literature, and heating of the materials is very likely to occur in these settings and cause similar emissions, and thus similar exposures to workers. IARC does, however, include exposure during mastic asphalt work, but this is not known to occur in Canada so we have not considered it further in our estimates.1
Since a wide variety of compounds are released into the air when bitumens are heated, respiratory exposure to bitumens have been studied by measuring many agents. These agents include total particulate, volatile organic compounds, fumes released as cyclohexane- or benzene-soluble matter, and various PAHs. For this reason, there is likely to be some overlap between PAH exposure and bitumens exposure in our CAREX estimates.
To determine the number of workers potentially exposed to bitumens at work, CAREX occupational exposure experts used methods previously established in other peer-reviewed CAREX projects in Europe, in addition to new information available in the recent IARC evaluation of bitumens. A series of steps were taken to assign exposure proportions to occupations and industries at risk of exposure to bitumens.
- Occupations and industries at risk of possible exposure to bitumens 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 judgment 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 bitumens.