Results show that approximately 7,700 Canadians are exposed to naphthalene at work; 91% of these workers are male. Industries with the highest number of exposed workers are alumina/aluminum production and processing (naphthalene emission from graphite electrodes), petroleum and coal products manufacturing (where pure naphthalene and coke are manufactured), and wood preservation (where naphthalene is vapourized from creosote).
When exposure is examined by occupation, important occupational groups exposed include petroleum, gas and chemical process operators (1,400 exposed), machine operators in mineral and metal processing (1,300 exposed), and labourers in mineral and metal processing (900 exposed).
Data Sources & Methods
Data used in developing the occupational estimates for naphthalene were collected from several sources:
- The Canadian Workplace Exposure Database (CWED) contains approximately 200 measurements for naphthalene 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 naphthalene exposure in Canada and the United States.
- Grey literature including technical reports from governments and international bodies.
Prevalence Estimate Method
CAREX defines exposure to naphthalene as inhalation exposure at work at levels exceeding those encountered in non-occupational settings, such as exposure due to inhaling urban air (i.e. from incomplete combustion) and/or indoor air (i.e. from mothballs). Naphthalene is a polycyclic aromatic hydrocarbon (PAH), but exposure here is intended to reflect industries and occupations where it occurs as an industrial product, rather than as a mixed product of incomplete combustion. Further information on PAHs can be found elsewhere on the CAREX Canada website.
To determine the number of workers potentially exposed to naphthalene 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 naphthalene.
- Occupations and industries at risk of possible exposure to naphthalene 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 naphthalene.