Investigating the Occupational Etiology of Prostate Cancer in Canadian Workers

Prostate cancer is one of the most commonly diagnosed cancers worldwide and is expected to remain as one of the most commonly diagnosed cancers in the decades to come. The etiology of prostate cancer is poorly understood and aside from few non-modifiable factors (age, family history of prostate cancer, and ethnicity), there is limited understanding of modifiable risk factors for prostate cancer, including occupation. Previous studies have reported inconsistent findings between occupation, industry, and prostate cancer with weak associations for farming and agriculture, rubber manufacturing, and transportation. In Canada, there have been very few large population studies that include a range of occupation and industry groups, prostate cancer outcomes, and information on non-occupational factors. Given that prostate cancer will remain as one of the most common cancers in men, and given that there are no established preventable risk factors for prostate cancer, further evidence on risk factors like occupation is needed.

This study used multiple Canadian population-based datasets (both case-control and cohort studies) to assess prostate cancer risk in all occupations and industries, followed by a meta-analysis that was conducted on specific occupations identified in the population-based datasets.

The three major datasets used in this project include:

• The Northeastern Ontario Prostate Cancer Study
• The National Enhanced Cancer Surveillance System (NECSS)
• The Canadian Census Health & Environment Cohort (CanCHEC)

Significant associations between natural resource based (agriculture, forestry, logging, wood, paper), white collar, protective services (firefighters, police, and armed forces), construction, transportation, and prostate cancer risk were observed in the three population studies. Consistent evidence for increased prostate cancer incidence and mortality among firefighting and police work was observed in the meta-analysis. Specific job-related exposures to be considered are pesticides, diesel exhaust, whole body vibrations, wood dust, wood preservative chemicals, shift work, among other factors of sedentary behaviour, stress, and screening patterns. The results indicate the need for more focused studies with better exposure assessment methods and improved understanding of related non-occupational factors. Overall, the results of this work provide strong evidence associating specific occupations to prostate cancer risk.

The results of this study improve our understanding on occupation and prostate cancer risk, while also providing stronger evidence from Canadian population-based studies. The identified occupations and industries also provide insight into potential job-specific exposures to be considered. Also, other non-occupational factors are important in the relationship between occupation and prostate cancer risk. Examining these factors together will inform prevention strategies for job-specific exposure and prostate cancer risk reduction. The evidence from this project can improve knowledge on the occupational etiology of prostate cancer, ultimately informing policies and programs for reduction in prostate cancer risk.