Among Canadians, urinary bladder cancer is the fifth most common cancer diagnosis [1]. Men are three times more likely to be diagnosed with bladder cancer than women. The most prominent and well-established risk factor for this cancer is tobacco smoking. Other non-occupational risk factors include exposure to arsenic in drinking water and radiation during medical treatment.
Bladder cancer is an important occupational disease. There is strong evidence of an association between bladder cancer and several workplace exposures. The Occupational Cancer Research Centre estimates that between 3-12% of bladder cancers in Canada are attributable to occupational exposures [2]. Although some known bladder carcinogens have declined in use since the 1980s, other suspected agents remain common in the workplace. Research conducted by the OCRC indicates that an estimated 280 bladder cancer cases per year in Canada may be attributable to workplace diesel engine exhaust and polycyclic aromatic hydrocarbon exposure alone [2].
Known occupational risk factors
Possible occupational risk factors
Increased risks of bladder cancer were observed among workers in transportation, construction and metal manufacturing, and some managerial and administrative occupations. Increased risk of bladder cancer was observed among some workers in rubber and plastics processing occupations, although estimates for workers in this sector overall were lower than expected. Occupational variation in smoking may contribute to observed differences in bladder cancer risk. Too few cases were observed among hair dressers and barbers and dry cleaners to examine the risk of bladder cancer for these groups.
Many workers in transportation occupations are regularly exposed to diesel engine exhaust, which is a suspected bladder carcinogen.
Overall, construction workers showed only a slightly increased risk of bladder cancer, but some trades were associated with higher risks. Construction workers may be exposed to diesel engine exhaust, a known bladder carcinogen, and may also be exposed to solvents and fumes which could be linked to bladder cancer risk.
Metalworkers are exposed to a variety of occupational hazards, including metal dusts, welding fumes and chemical solvents. Metalworkers can be exposed to known bladder carcinogens, such as aromatic amines through use of metalworking fluids and polycyclic aromatic hydrocarbons (PAHs) in foundry processes. Excess risks were also observed for workers in some primary metal industries, including aluminum, with exposure to PAHs and other known and suspected bladder carcinogens.
Historically, manufacturing processes in rubber and plastics industries used aromatic amines, which are now known bladder carcinogens [4]. However, the use of many aromatic amines has declined in manufacturing processes in Canada since the 1980s due to legislative control. We observed a slightly elevated risk of bladder cancer among workers in rubber manufacturing industries in Ontario, and we observed elevated risk in some specific occupation groups, although the number of cases in these groups was relatively few. Bladder cancer risks from the rubber and plastics industries are described in more detail by DeBono et al. [6].
Excess risks among these occupations could be related to environmental, lifestyle, or tobacco-related exposures. Printing processes have been classified as possibly carcinogenic by IARC, but evidence for bladder cancer was weak [7].
Figure 1. Risk of bladder cancer diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 1999-2016
The hazard ratio is an estimate of the average time to diagnosis among workers in each industry/occupation group divided by that in all others during the study period. Hazard ratios above 1.00 indicate a greater risk of disease in a given group compared to all others. Estimates are adjusted for birth year and sex. The width of the 95% Confidence Interval (CI) is based on the number of cases in each group (more cases narrows the interval).
Figure 2. Risk of bladder cancer diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 1999-2016
Table 1. Surveillance of Bladder Cancer: Number of cases, workers employed, and hazard ratios in each industry (SIC)
Table 2. Surveillance of Bladder Cancer: Number of cases, workers employed, and hazard ratios in each occupation (CCDO) group
Please note that ODSS results shown here may differ from those previously published or presented. This may occur due to changes in case definitions, methodological approaches, and the ongoing nature of the surveillance cohort.
