The largest industrial groups exposed include freight trucking, local, municipal and regional public administration, and offices of real estate agents and brokers​. Occupations at risk of gasoline engine exhaust exposure include transport truck drivers, delivery and courier service drivers, bus drivers, subway operators and other transit operators, and real estate agents and salespersons.

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 gasoline engine exhaust were collected from several sources:

1. The Canadian General Population Job-Exposure Matrix (CANJEM), which was built from expert evaluations of occupational exposures in four case-control studies conducted from the mid-1980s up to 2010 in the greater Montreal area. Approximately 10,000 individuals were evaluated by experts who assigned exposures based on descriptions of work tasks, processes, work environment, and exposure control measures.
2. Canadian and US scientific peer reviewed publications that addressed gasoline engine exhaust 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 gasoline engine exhaust as inhalation exposure at work above the levels expected in the general environment (i.e. from living close to a highway). To determine the number of workers potentially exposed to gasoline engine exhaust 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 gasoline engine exhaust.

1. Occupations and industries at risk of possible exposure to gasoline engine exhaust 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 gasoline engine exhaust.

Exposure Level Method

CAREX regularly uses available workplace exposure measurements in the CWED to create exposure level categories by industry and occupation. For gasoline engine exhaust, these were not available due to a lack of a regulatory exposure limits. Therefore, categories of exposure were created as follows:

Category 1: Low Exposure

A group of workers (people in the same job category and industry) is put in this exposure category if:

1. Workers occasionally spend time working with or near gas engine equipment, or
2. Workers spend a considerable portion of the workday in high-traffic areas.

Category 2: Moderate Exposure

A group of workers is put in this exposure category if:

1. Workers directly work with gas-powered equipment, or
2. They work in close proximity to gas-powered equipment.

Category 3: High Exposure

A group of workers is put in this exposure category if they directly use gas-powered equipment/vehicles/devices in spaces with reduced ventilation (e.g. in indoor environments, with partial covering of the workspace).