Although exposure to formaldehyde has decreased over time, exposure still occurs in a wide variety of occupations and industries. Hospitals and full-service restaurants and limited service eating places are among the largest exposed industrial groups in Canada. In terms of occupations, the largest groups of workers exposed to formaldehyde are cooks, motor vehicle assemblers, inspectors and testers, registered nurses and registered psychiatric nurses, and furniture and fixture assemblers and inspectors.

In wood panel manufacturing, formaldehyde is released when heating adhesives, which can expose press operating and maintenance workers.[3] In furniture manufacturing, formaldehyde is released when preparing and applying varnishes or paints (especially when applied with a spray gun), and drying. Therefore, painters, manual labourers working at dryers, and maintenance workers can also be exposed.[3]

Other occupations with acute exposure to formaldehyde include embalmers, pathology lab workers, wood, and pulp and paper processing workers. Health care professionals (nurses, dentists, and pharmacists) may also be exposed while using or cleaning up medical products and equipment.[4,5]

Workers involved in producing resins, man-made vitreous fibres, and plastic products are potentially exposed to formaldehyde. Levels are expected to be low, however, because of improved ventilation and the development of resins that release less formaldehyde.[4]

According to the Burden of Occupational Cancer in Canada project, occupational exposure to formaldehyde leads to approximately five leukemia and less than five nasopharyngeal cancers each year in Canada, based on past exposures (1961-2001).[6,7] This amounts to 0.1% of all leukemia and 0.8% of all nasopharyngeal cancers cancers diagnosed annually. Most formaldehyde-related cancers occur among workers in the manufacturing sector.[7]

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 formaldehyde were collected from several sources:

1. The Canadian Workplace Exposure Database (CWED) contains over 10,500 measurements for formaldehyde 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 formaldehyde 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 formaldehyde as inhalation and/or dermal exposure at work, at levels exceeding those encountered in the general environment (excluding exposure to cigarette smokers).

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

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

Exposure Level Method

CAREX uses available workplace exposure measurements in the CWED to create exposure level categories by industry and occupation. For formaldehyde, 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 0.5 ppm (which is a threshold level for moderate exposure chosen by CAREX Canada for risk of nasopharyngeal cancer¹).

OR

1. There are at least 10, but less than 25, individual samples in the CWED, AND
2. 20% or more samples have a value higher than 1.0 ppm (which is a threshold level for high exposure chosen by CAREX Canada for risk of nasopharyngeal cancer¹).

Category 3: High 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 1.0 ppm (which is a threshold level for high exposure chosen by CAREX Canada for risk of nasopharyngeal cancer¹).

1. Hauptmann M, Lubin JH, Stewart PA, Hayes RB, Blair A. ‘Mortality from solid cancers among workers in formaldehyde industries.‘ Am. J Epidemiol. 2004 Jun 15;159(12):1117-30.