Identification of occupational cancer risks in British Columbia, Canada: a population-based case-control study of 1,155 cases of colon cancer

Our plain-English summary of Identification of occupational cancer risks in British Columbia, Canada: a population-based case-control study of 1,155 cases of colon cancer, by R. Fang, N. Le, P. Band (International Journal of Environmental Research and Public Health, 2011).

The study

• Authors: R. Fang, N. Le, P. Band
• Journal: International Journal of Environmental Research and Public Health
• Published: 2011;8(10):3821-43
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Cancer has been recognized to have environmental origin, but occupational cancer risk studies have not been fully documented. The objective of this paper was to identify occupations and industries with elevated colon cancer risk based on lifetime occupational histories collected from 15,463 incident cancer cases.

Method: A group matched case-control design was used. All cases were diagnosed with histologically proven colon cancers, with cancer controls being all other cancer sites, excluding rectum, lung and unknown primary, diagnosed at the same period of time from the British Columbia Cancer Registry. Data analyses were done on all 597 Canadian standard occupation titles and 1,104 standard industry titles using conditional logistic regression for matched data sets and the likelihood ratio test.

Results: Excess colon cancer risks was observed in a number of occupations and industries, particularly those with low physical activity and those involving exposure to asbestos, wood dusts, engine exhaust and diesel engine emissions, and ammonia.

Discussion: The results of our study are in line with those from the literature and further suggest that exposure to wood dusts and to ammonia may carry an increased occupational risk of colon cancer.

In plain English

This population-based case-control study used lifetime job questionnaires from male cancer patients ascertained by the British Columbia Cancer Registry from 1983 to 1990. It compared 1,155 men with colon cancer with 7,552 men with other cancers, excluding lung, rectum and unknown primary, matched on age and diagnosis year. Asbestos exposure was not measured; in the discussion, the authors described some job groups as exposed to asbestos. Rail transport equipment mechanics and repairers had odds ratios of 3.84 (95% CI 1.82 to 8.11, 11 cases) for ever holding the job and 6.06 (2.04 to 18.00, 6 cases) as usual job. Usual-occupation odds ratios were raised for ship engineering officers (4.80, 1.81 to 12.71, 7 cases) and brick and stone masons-tile setters (2.97, 1.20 to 7.34, 7 cases); the usual-industry odds ratio for exterior close-in masonry work was 3.02 (1.03 to 8.89, 5 cases). The authors noted results could reflect chance from multiple comparisons and small numbers. They concluded that their findings agree with the literature on asbestos and engine exhaust and suggest wood dust and ammonia may raise colon cancer risk.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Population-based, group-matched case-control study using other cancer patients as controls; conditional logistic regression applied to every occupation and industry title
• Who was studied: Male cancer patients aged 20 and over ascertained by the British Columbia Cancer Registry, 1983 to 1990. Questionnaires on colon cancer were sent to 1,768 eligible cases and 1,156 (65.4%) were returned. After matching, 1,155 colon cancer cases were compared with 7,552 controls who had other cancers (excluding lung, rectum and unknown primary site).
• Exposure: Self-reported lifetime occupation and industry, coded to 597 Canadian standard occupation titles and 1,104 industry titles. These were analysed as 'ever' versus never and as 'usual' (longest-held) job versus never. No measured exposures were available. The authors attributed asbestos exposure to certain jobs, including rail transport equipment mechanics, masons and ship engineering officers.
• Main results:
  • Rail transport equipment mechanics and repairers: ever held the job, 11 cases, OR 3.84 (p less than 0.001, 95% CI 1.82 to 8.11); usual job, 6 cases, OR 6.06 (p 0.001, 95% CI 2.04 to 18.00). The authors described this group as exposed to asbestos.
  • Ship engineering officers: usual occupation, 7 cases, OR 4.80 (p 0.002, 95% CI 1.81 to 12.71); ever held, 10 cases, OR 1.56 (95% CI 0.77 to 3.17, not significant). The authors described this group as exposed to exhaust gases, engine emissions and asbestos.
  • Brick and stone masons, tile setters: usual occupation, 7 cases, OR 2.97 (p 0.018, 95% CI 1.20 to 7.34); ever held, 9 cases, OR 1.29 (95% CI 0.62 to 2.67, not significant).
  • Exterior close-in masonry work (an industry category, SIC 4231): usual industry, 5 cases, OR 3.02 (p 0.045, 95% CI 1.03 to 8.89).
  • Construction, mining machinery and materials handling industry: usual industry, 5 cases, OR 3.66 (p 0.023, 95% CI 1.19 to 11.22). The authors grouped this with the jobs they linked to asbestos.
  • Insurance sales, a sedentary occupation: ever held, 31 cases, OR 1.81 (95% CI 1.19 to 2.76); usual job, 9 cases, OR 2.22 (95% CI 1.02 to 4.81).
• The authors' conclusion: The authors concluded that their results are in line with the literature on elevated colon cancer risk from asbestos and from engine exhaust and diesel emissions. They also concluded that the results suggest wood dust and ammonia exposure may carry an increased risk. They called for more specific studies using population controls.
• Limitations the authors state:
  • No information on actual occupational exposures was available.
  • Statistically significant results may have occurred by chance because of multiple comparisons.
  • Case numbers were small, especially for many usual occupations and industries.
  • The control group of other cancer patients may not represent the general population. If other cancers share occupational risks with colon cancer, the odds ratios would underestimate true risks.
  • Body-mass index and physical activity were not collected.
  • Some observed risks may not apply to current workers because industrial exposures may have decreased.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Colon cancer.

Medical terms in this study, explained in our Lexicon: Case-Control Study, Colorectal Cancer, Cancer Registry.

Related studies

• Identification of occupational cancer risk in British Columbia: a population-based case-control study of 2,998 lung cancers by histopathological subtype — A.C. MacArthur, N.D. Le, et al. (2009)
• A case-control study of the relationship between the risk of colon cancer in men and exposures to occupational agents — M.S. Goldberg, M.E. Parent, et al. (2001)
• Do patterns of past asbestos use and production reflect current geographic variations of cancer risk?: mesothelioma in Ontario and British Columbia, Canada — C.E. Slavik, P.A. Demers, et al. (2023)
• Cohort mortality study of pulp and paper mill workers in British Columbia, Canada — P.R. Band, N.D. Le, et al. (1997)
• Occupational asbestos exposure as a risk factor for laryngeal carcinoma in a population-based case-control study from Germany — H. Ramroth, W. Ahrens, et al. (2011)
• Risk of lung cancer associated with occupational exposure to mineral wools: updating knowledge from a french population-based case-control study, the ICARE study — F. Guida, S. Paget-Bailly, et al. (2013)

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