Results show that approximately 25,000 Canadians are exposed to dichloromethane (DCM) in their workplaces; 83% of these workers are male. Industries with the highest number of exposed workers are those involved in paint removal, which includes auto-body shops, furniture restoration (personal and household goods repair and maintenance, and construction (building finishing contractors).
When exposure is examined by occupation, the largest exposed groups are motor vehicle body repairers (4,100 exposed), painters and decorators (1,900 exposed) and machinists and machining and tooling inspectors (1,700 exposed). Machining workers are exposed to dichloromethane via its use as a degreasing agent.
Level of Exposure
In total, approximately 25,000 Canadians are exposed to dichloromethane in their workplaces. The majority of workers exposed to dichloromethane are in the low exposure category. A substantial number of dichloromethane-exposed workers are at risk for moderate and high exposure.
Level of Exposure by Industry
Identifying industries with either 1) workers exposed to high levels of dichloromethane or 2) a larger number of workers exposed to dichloromethane is important in guiding cancer prevention efforts to prioritize exposed groups and target resources most effectively.
The table below shows the number of workers exposed by industry group and level of exposure to dichloromethane. These results highlight industries with the most number of workers, as well as industries with the highest levels of exposure. Data for those industries with at least 500 workers exposed is shown.
For example, in the repair and maintenance industry, nearly all of the workers fall into the low exposure category. However, in the plastics and rubber products industry, most of the exposed workers (73%) are in the high exposure category. Depending on the goals of a prevention campaign, exposure reduction in the large industrial group might be a useful strategy, or reducing exposure to those at highest risk of exposure could be seen as a priority.
|Low Exposure (n)||Moderate Exposure (n)||High Exposure (n)||Total Workers Exposed (n)|
|811: Repair and maintenance||5,400||100||800||6,200|
|238: Specialty trade contractors||1,600||1,900||0||3,500|
|326: Plastics and rubber products manufacturing||200||500||2,000||2,800|
|333: Machinery manufacturing||1,300||1,200||0||2,500|
|336: Transportation equipment manufacturing||0||2,200||0||2,200|
|325: Chemical manufacturing||500||600||400||1,500|
|332: Fabricated metal product manufacturing||400||600||0||1,000|
|441: Motor vehicle and parts dealers||900||0||0||900|
|323: Printing and related support activities||200||500||0||600|
Published April 2013
Data Sources & Methods
Data used in developing the occupational estimates for dichloromethane (DCM) were collected from several sources:
- 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.
- Canadian and US scientific peer reviewed publications that addressed DCM exposure in Canada and the United States.
- 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.
- Occupations and industries at risk of possible exposure to DCM 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 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:
- The are no valid measurements, but a hygienist identified this group as typically exposed during literature and other reviews;
- There are valid exposure measurements in the CWED and a hygienist review determined that exposure is plausible; AND EITHER:
- There are less than 10 samples available in the CWED, OR
- 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:
- There are at least 25 individual samples in the CWED, AND
- 20% or more samples have a value higher than 25 ppm (which is ½ of the current occupational exposure limit for dichloromethane),
- There are at least 10 individual samples in the CWED, AND
- 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:
- There are at least 25 individual samples in the CWED, AND
- 2. 20% or more samples have a value higher than 50 ppm (which is the current occupational exposure limit for dichloromethane).