Bladder Cancer

Background
 
What is bladder cancer?

Among Canadians, urinary bladder cancer is the fifth most common cancer diagnosis. 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 for abdominal diseases.

Bladder cancer is an important occupational disease. There is strong evidence of an association between bladder cancer and several workplace exposures, including dyes, paints, and chemicals involved in aluminum and rubber manufacturing. There is also growing evidence that diesel engine exhaust and polycyclic aromatic hydrocarbons (produced by burning oils, wood and other organic products) may cause bladder cancer. The Occupational Cancer Research Centre estimates that between 3-12% of bladder cancers in Canada are attributable to occupational exposures (Labrèche et al, 2019).

Although some known bladder carcinogens have declined in use since the 1980s, other suspected agents remain prevalent 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.

 

Known occupational risk factors
    • Aromatic amines (benzidine, Auramine O, 2-naphthylamine, o-toluidine, 4-aminobiphenyl)
    • Arsenic and inorganic arsenic compounds
    • Aluminum production
    • Painting (occupation)
    • Rubber production 
Possible occupational risk factors
    • Diesel engine exhaust
    • Polycyclic aromatic hydrocarbons
    • Tetrachloroethylene
    • Hair dressers and barbers (occupation)
    • Welding (occupation)
Key Findings

Increased risks of bladder cancer are observed among workers in transportation, construction, metal manufacturing, janitorial, managerial, and administrative occupations. Increased risk of bladder cancer is observed among some workers in rubber and plastics processing occupations, although estimates for workers in this sector overall were lower than expected.


Transportation

Overall, workers in transportation occupations have an increased risk of bladder cancer. Truck drivers, bus drivers and taxi drivers each demonstrate increased risk of the disease. Additionally, workers in air transport operating and railway transport operating occupations are at increased risk. Many workers in transportation occupations are regularly exposed to diesel engine exhaust, which is a suspected bladder carcinogen.

    • All transportation occupations: 1.3 times the risk
      • Truck drivers: 1.3 times the risk
      • Bus drivers: 1.4 times the risk
      • Taxi drivers: 1.5 times the risk
      • Air transport operating occupations: 3.4 times the risk
      • Railway transport operating occupations: 1.3 times the risk
Construction

Overall, construction workers showed a slightly increased risk of bladder cancer. Workers within excavating, grading, and paving occupations are at an increased risk, as are bricklayers, stonemasons, and tile setters. Concrete finishers, plumbers, and painters are also at an increased risk.

    • All construction occupations: 1.1 times the risk
      • Excavating, grading, and related occupations: 1.6 times the risk
      • Bricklayers, stonemasons, and tile setters: 1.4 times the risk
      • Concrete finishers and related occupations: 1.7 times the risk
      • Pipefitters and plumbers: 1.3 times the risk
      • Painters and paperhangers: 1.2 times the risk
Metal manufacturing

Metalworkers are exposed to a host of occupational hazards, including metal dusts, welding fumes and chemical solvents. Workers in metal manufacturing industries are at an increased risk of bladder cancer. Specifically, foremen within metal machining, processing, and shaping and forming occupations are at an increased risk. Many foremen may have worked in the trades they supervised, prior to becoming foremen. Additionally, boilermakers, platers, and structural metalworkers; workers in forging occupations; and iron and steel mill workers are also at an increased risk of bladder cancer.

    • Foremen – metal machining: 1.5 times the risk
    • Foremen – metal processing: 1.2 times the risk
    • Foremen – metal shaping and forming: 1.5 times the risk
    • Boilermakers, platers, and structural metalworkers: 1.8 times the risk
    • Forging occupations: 1.9 times the risk
    • Iron and steel mill workers: 1.3 times the risk
Janitors and cleaners

Janitors and cleaners showed an increased risk of bladder cancer in the ODSS. They frequently handle cleaning products, which can lead to inhalation and dermal exposure to these chemicals.

    • Janitors and cleaners: 1.3 times the risk
 
Rubber and plastics industries

Previous evidence has shown that workers in rubber and plastics manufacturing industries are at increased risk of bladder cancer. Historically, manufacturing processes in these industries used aromatic amines, which are now known bladder carcinogens. However, the use of many aromatic amines has declined in manufacturing processes in Canada since the 1980s due to legislative control. We did not find elevated risks of bladder cancer among all workers in plastics and rubber manufacturing industries in Ontario, although we observed elevated risk in some specific occupation groups. This could be explained by past legislative changes to ban certain carcinogenic chemicals in these industries.

    • Overall, rubber and plastics industries: No elevated risk
      • Rubber products industries: No elevated risk
      • Plastics fabricating industries: No elevated risk
    • Chemicals, petroleum, rubber, plastic and related materials processing occupations: 1.2 times the risk
    • Foremen – fabricating, assembling and repairing occupations, rubber, plastic and related products: 1.7 times the risk
    • Manufacturers of plastics and synthetic resins: 1.5 times the risk
White collar occupations

Increased risks of bladder cancer were observed among salespersons, managers, administrators, and workers in the education and related services industry. There are no clear occupational risk factors for bladder cancer in these groups. These findings could be related to environmental, lifestyle, or tobacco-related exposures.

    • Salesmen and salespersons, commodities: 2.1 times the risk
    • Management & administrators: 1.5 times the risk
    • Provincial administrative workers: 1.1 times the risk
    • Education and related services: 2.4 times the risk
Relative Risk by Industry and Occupation

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 

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).

Table of Results

Table 1. Surveillance of Bladder Cancer: Number of cases, workers employed, and hazard ratios in each industry (SIC)

SIC Code * Industry Group Number of cases Number of workers employed Hazard Ratio (95% CI) †
1 Agriculture 132 35,109 0.81 (0.68, 0.96)
2/3 Forestry, Fishing and Trapping 55 10,720 0.63 (0.49, 0.83)
4 Mines, Quarries and Oil Wells 229 23,218 1.03 (0.90, 1.17)
5 Manufacturing 4,389 694,665 0.95 (0.91, 0.98)
6 Construction 1,340 211,488 1.01 (0.95, 0.98)
7 Transportation, Communication and Other Utilities 1,305 197,483 1.13 (1.06, 1.19)
8 Trade 1,775 429,827 0.98 (0.94, 1.04)
9 Finance, Insurance and Real Estate 144 24,006 1.08 (0.92, 1.28)
10 Community, Business and Personal Service 1,995 600,255 1.01 (0.96, 1.06)
11 Public Administration and Defense 1,225 191,040 1.16 (1.09, 1.23)
         
* SIC: Standard Industrial Classification (1970)    
† Hazard ratio in each group relative to all others    

 

Table 2. Surveillance of Bladder Cancer: Number of cases, workers employed, and hazard ratios in each occupation (CCDO) group

CCDO Code * Occupation Group Number of cases Number of workers employed Hazard Ratio (95% CI) †
11 Managerial, administrative
and related
144 31,014 1.46 (1.24, 1.72)
21 Natural sciences, engineering
and mathematics
140 26,362 1.15 (0.97, 1.35)
23 Social sciences and
related fields
46 30,719 0.84 (0.63, 1.12)
25 Religion 0 129
27 Teaching and related 135 48,509 1.13 (0.95, 1.34)
31 Medicine and health 304 135,445 0.92 (0.82, 1.04)
33 Artistic, literary,
recreational and related
48 14,997 1.25 (0.94, 1.66)
41 Clerical and related 864 197,525 1.17 (1.09, 1.25)
51 Sales 500 148,202 1.28 (1.17, 1.40)
61 Service 1,615 371,226 1.11 (1.05, 1.17)
71 Farming, horticultural
and animal husbandry
175 50,256 0.77 (0.66, 0.89)
73 Fishing, hunting,
trapping and related
<5 558
75 Forestry and logging 61 10,709 0.73 (0.57, 0.94)
77 Mining and quarrying,
including oil and gas field
129 13,039 1.07 (0.90, 1.27)
81 Processing
(mineral, metal, chemical)
443 79,365 1.01 (0.92, 1.11)
82 Processing
(food, wood, textile)
454 99,347 0.95 (0.86, 1.04)
83 Machining and related 1,315 189,703 1.07 (1.01, 1.13)
85 Product fabricating,
assembling and repairing
2,075 328,689 1.02 (0.97, 1.07)
87 Construction trades 1,617 216,033 1.10 (1.04, 1.16)
91 Transport equipment
operating
1,338 168,387 1.31 (1.24, 1.39)
93 Materials handling and related,
not elsewhere classified
786 153,278 0.98 (0.91, 1.05)
95 Other crafts and
equipment operating
205 28,349 1.16 (1.01, 1.33)
99 Other occupations not elsewhere classified 1,093 215,548 0.96 (0.90, 1.02)
         
* CCDO: Canadian Classification Dictionary of Occupations (1971)  
† Hazard ratio in each group relative to all others    

 

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.