PROSTATE CANCER

Prostate Cancer

Background

What is prostate cancer?

In Canada, prostate cancer is the most commonly diagnosed cancer among men. Important risk factors for prostate cancer include age and family history, however, little is known about the modifiable risk factors for the disease, including occupational causes. Occupational exposures that affect the endocrine system, such as shift work, are of particular interest given that prostate cancer can be a hormone-sensitive malignancy.

Possible occupational risk factors

These exposures are possible risk factors for prostate cancer, but evidence is currently inconclusive.

- - Metallic compounds (e.g. cadmium and arsenic)
  - Exposure to x- and gamma-radiation
  - Chemical exposures (e.g. rubber compounds, pesticides such as malathion, and diesel exhaust)
  - Sedentary behaviour and physical inactivity
  - Work-related psychological stress
  - Shift work
  - Whole body vibration

Key Findings

The greatest risks of prostate cancer were observed among workers employed in management and administration, transportation, construction and trades, firefighting, and police occupations.

White collar occupations

Increased risks of prostate cancer are observed across all management and administrative occupations, as well as in teaching occupations. A possible explanation for these findings could be increased sedentary behavior and low occupational physical activity in white collar work. Additionally, this finding could be related to a greater uptake of prostate cancer screening in this group relative to others. Given that many prostate tumours grow slowly, more frequent screening could have increased the number of diagnoses in this group that would not have been detected otherwise.

- Management and administration: 2.2 times the risk
- Teaching: 1.2 times the risk

Transportation

Employment in multiple transportation occupations is associated with an increased risk of prostate cancer, including railway transport operating, motor transport operating, and stationary engine and utilities operating. Possible exposures that could lead to an increased risk of prostate cancer in these groups include sedentary behavior and physical inactivity, shift work, obesity and whole body vibration. Exposure to whole body vibration occurs when mechanical energy from vibrating surfaces is passed to the body either in standing or sitting positions. Although the role of whole body vibrations in prostate cancer etiology remains unclear, other prostate conditions like prostatitis and increasing testosterone levels have been linked to whole body vibration exposure.

- Transportation occupations: 1.2 times the risk

Metal product manufacturing

Elevated risks of prostate cancer are observed for metal-related occupations such as metal processing, metal machining, metal shaping and forming, and metal product fabricating and assembling. These types of jobs may expose workers to elevated levels of metallic compounds or whole body vibration, which are possible risk factors for prostate cancer.

- Foremen, metal processing and related: 1.9 times the risk
- Metal rolling: 1.5 times the risk
- Foremen, metal machining: 1.7 times the risk
- Foremen, metal shaping and forming (except machining): 2.2 times the risk
- Metal forging: 1.5 times the risk

Emergency services

Elevated risk of prostate cancer is observed in both firefighters and police. This could be related to shift work, sedentary behaviour or high levels of occupational stress among these groups. Firefighters may also be exposed to diesel engine exhaust while working in fire halls, which is a potential risk factor for prostate cancer.

- Firefighters: 1.6 times the risk
- Police: 1.2 times the risk

Relative Risk by Industry and Occupation

Figure 1. Risk of prostate cancer diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2016

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 prostate cancer diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2016

Table of Results

Table 1. Surveillance of Prostate 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	361	26,402	0.60 (0.54, 0.67)
2/3	Forestry, Fishing and Trapping	213	10,223	0.79 (0.69, 0.90)
4	Mines, Quarries and Oil Wells	738	22,707	1.27 (1.18, 1.37)
5	Manufacturing	14,064	528,890	1.01 (0.99, 1.04)
6	Construction	4,077	202,142	0.86 (0.83, 0.89)
7	Transportation, Communication and Other Utilities	4,309	164,173	1.20 (1.16, 1.24)
8	Trade	5,200	291,020	0.74 (0.72, 0.76)
9	Finance, Insurance and Real Estate	429	15,220	1.31 (1.19, 1.44)
10	Community, Business and Personal Service	4,660	249,204	0.89 (0.87, 0.92)
11	Public Administration and Defense	4,026	121,480	1.49 (1.44, 1.54)

* SIC: Standard Industrial Classification (1970)
† Hazard ratio in each group relative to all others

Table 2. Surveillance of Prostate 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	464	14,228	2.17 (1.98, 2.38)
21	Natural sciences, engineering and mathematics	538	20,814	1.30 (1.20, 1.42)
23	Social sciences and related fields	128	6,834	1.10 (0.92, 1.31)
25	Religion	<5	79	—
27	Teaching and related	353	10,018	1.99 (1.79, 2.21)
31	Medicine and health	362	17,068	1.14 (1.03, 1.27)
33	Artistic, literary, recreational and related	156	8,400	1.11 (0.95, 1.30)
41	Clerical and related	2,133	96,316	1.00 (0.96, 1.04)
51	Sales	1,163	71,727	0.88 (0.83, 0.94)
61	Service	4,221	187,123	1.07 (1.04, 1.11)
71	Farming, horticultural and animal husbandry	586	39,236	0.68 (0.63, 0.74)
73	Fishing, hunting, trapping and related	8	518	0.66 (0.33, 1.33)
75	Forestry and logging	183	10,109	0.67 (0.58, 0.77)
77	Mining and quarrying, including oil and gas field	422	12,870	1.31 (1.19, 1.44)
81	Processing (mineral, metal, chemical)	1,403	62,878	0.93 (0.88, 0.98)
82	Processing (food, wood, textile)	1,372	67,325	0.87 (0.82, 0.91)
83	Machining and related	4,428	168,127	1.07 (1.04, 1.11)
85	Product fabricating, assembling and repairing	7,156	261,187	1.12 (1.09, 1.14)
87	Construction trades	5,284	211,378	1.09 (1.06, 1.12)
91	Transport equipment operating	3,998	153,882	1.20 (1.16, 1.24)
93	Materials handling and related, not elsewhere classified	2,392	121,957	0.80 (0.76, 0.83)
95	Other crafts and equipment operating	619	21,541	1.15 (1.06, 1.24)
99	Other occupations not elsewhere classified	3,554	174,651	0.85 (0.82, 0.88)

* 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.