The largest industrial groups exposed are automotive repair and maintenance, followed by building finishing contractors and plastic product manufacturers. Other important industries that are likely exposed include building equipment contractors and personal and household goods maintenance and repair.

The largest exposed occupational groups are motor vehicle body repairers, followed by painters and decorators, construction traders helpers and labourers, and machinist and machining and tooling inspectors. Other occupations that may be exposed include furniture refinishers and chemical manufacturers.[1] Workers may be exposed when spraying urethane foam, removing paint or varnish from equipment or furniture, or using products that use dichloromethane as a propellant or degreasing agent.

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 dichloromethane (DCM) were collected from several sources:

1. The Canadian Workplace Exposure Database (CWED) contains over 5,100 measurements for DCM 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 DCM 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 DCM as inhalation or dermal exposure at work to levels significantly greater than those encountered in outdoor or indoor air due to short term use of formulated products.

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

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

Exposure Level Method

CAREX uses available workplace exposure measurements in the CWED to create exposure level categories by industry and occupation. For dichloromethane, these categories are:

Category 1: Low Exposure

A group of workers (people in the same job category and industry) is put in this exposure category for one of two reasons:

1. The are no valid measurements, but a hygienist identified this group as typically exposed during literature and other reviews;
2. There are valid exposure measurements in the CWED and a hygienist review determined that exposure is plausible; AND EITHER:
   1. There are less than 10 samples available in the CWED, OR
   2. There are ≥10 measurements available but they do not meet the criteria for Moderate Exposure.

Category 2: Moderate Exposure

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

1. There are at least 25 individual samples in the CWED, AND
2. 20% or more samples have a value higher than 25 ppm (which is ½ of the current occupational exposure limit for dichloromethane),

OR

1. There are at least 10 individual samples in the CWED, AND
2. 4. 20% or more samples have a value higher than 50 ppm (which is the current occupational exposure limit for dichloromethane).

Category 3: High Exposure

A group of workers is put in this exposure category if both these criteria are met:

1. There are at least 25 individual samples in the CWED, AND
2. 2. 20% or more samples have a value higher than 50 ppm (which is the current occupational exposure limit for dichloromethane).