Cancer incidence in sites potentially related to occupational exposures: 58 years of follow-up of firefighters in the Norwegian Fire Departments Cohort

Our plain-English summary of Cancer incidence in sites potentially related to occupational exposures: 58 years of follow-up of firefighters in the Norwegian Fire Departments Cohort, by N. Marjerrison, J. Jakobsen, T.K. Grimsrud, et al (Scandinavian Journal of Work, Environment & Health, 2022).

The study

• Authors: N. Marjerrison, J. Jakobsen, T.K. Grimsrud, J. Hansen, J.I. Martinsen, K.C. Nordby, M.B. Veierød, K. Kjærheim
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 2022;48(3):210-219
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: Firefighters are exposed to a variety of known and suspected carcinogens through their work. However, the association with cancer risk has limited evidence. We examined cancer incidence among firefighters in the newly established Norwegian Fire Departments Cohort restricted to sites with established associations with carcinogens encountered during firefighting. This included sites within the respiratory, urinary, and lympho-hematopoietic systems, and the skin and all sites combined.

Methods: Male firefighters (N=3881) in the cohort were linked to the Cancer Registry of Norway for incident cancer cases occurring during the period 1960-2018. We calculated standardized incidence ratios (SIR) with rates for the national male population as reference, and stratified SIR analyses by period of first employment, duration of employment, and time since first employment.

Results: Elevated risk was seen for all sites combined (SIR 1.15, 95% confidence interval 1.07-1.23). Elevated risk of urinary tract cancer was observed among firefighters who began working before 1950, and with observation ≥40 years since first employment. Risk of mesothelioma and laryngeal cancer were elevated with ≥40 years since first employment and with ≥30 years employment duration.

Conclusions: The observed associations between firefighting and urinary tract cancer, laryngeal cancer, and mesothelioma have been observed in some studies previously, and our results suggest the observed elevated risks are related to carcinogenic occupational exposures. Differences in risk by period of employment potentially reflect changes in exposures from improved quality and use of personal protective equipment.

In plain English

This retrospective cohort study followed 3881 male firefighters from 15 Norwegian fire departments. They were linked to the Cancer Registry of Norway for 1960 to 2018 and compared with all Norwegian men. Exposures were not measured; work as a firefighter stood in for exposure. There were 845 cancers, more than expected (SIR 1.15, 95% CI 1.07 to 1.23). Mesothelioma (7 cases) had the highest overall ratio (SIR 2.47 in the text, 2.46 in the table; 95% CI 0.99 to 5.06). The article does not separate pleural from peritoneal cases. Mesothelioma was elevated among men observed 40 or more years after first employment (6 cases; SIR 3.47, 95% CI 1.27 to 7.55) and among those employed 30 or more years (5 cases; SIR 3.09, 95% CI 1.00 to 7.20). Laryngeal cancer showed similar patterns. Urinary tract cancer was elevated among men who started before 1950. Lung cancer overall was near expected. The authors concluded their findings suggest the elevated risks are associated with firefighters' occupational exposures. They noted they had no lifestyle data and few cases for some cancers.

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: Retrospective cohort study comparing cancer incidence with the national male population (standardized incidence ratios), with registry linkage
• Who was studied: 3881 male firefighters who worked at 15 participating Norwegian fire departments between 1950 and 2019. Follow-up ran from 1 January 1960 to 31 December 2018, totalling 108 358 person-years. Female firefighters (43) and non-firefighting staff (667) were excluded.
• Exposure: Employment as a firefighter, used as a surrogate for exposure. No specific exposure measurements, including for asbestos, were available. Analyses were stratified by year of first employment, duration of employment and time since first employment.
• Main results:
  • All cancers combined, all male firefighters: 845 cases, SIR 1.15 (95% CI 1.07 to 1.23).
  • Mesothelioma, all male firefighters: 7 cases. The text gives SIR 2.47 and Table 2 gives 2.46 (95% CI 0.99 to 5.06). This was the highest overall SIR among the sites studied.
  • Mesothelioma among firefighters observed 40 or more years since first employment: 6 cases, SIR 3.47 (95% CI 1.27 to 7.55).
  • Mesothelioma among firefighters with employment duration of 30 or more years: 5 cases, SIR 3.09 (95% CI 1.00 to 7.20).
  • Laryngeal cancer was elevated with 40 or more years since first employment: SIR 3.33 (95% CI 1.60 to 6.13), 10 cases. It was also elevated with 30 or more years of employment: SIR 2.53 (95% CI 1.16 to 4.80), 9 cases.
  • Urinary tract cancer among firefighters who began working before 1950: 35 cases, SIR 1.71 (95% CI 1.19 to 2.38). Among those with 40 or more years since first employment: SIR 1.49 (95% CI 1.10 to 1.97).
  • Lung cancer overall: 81 cases, SIR 0.98 (95% CI 0.78 to 1.22). In the stratum 20 to 39 years since first employment it was lower than expected: SIR 0.64 (95% CI 0.40 to 0.98).
  • No elevated incidence was found for any subgroup of lympho-hematopoietic cancers.
• The authors' conclusion: The authors concluded that their findings suggest the elevated risks observed are associated with firefighters' occupational exposures. They suggested that differences by period of first employment may primarily reflect improved quality and use of personal protective equipment.
• Limitations the authors state:
  • No information on lifestyle factors such as smoking.
  • No specific exposure data; only exposure surrogates were used.
  • Low case numbers for some sites limit statistical power and precision.
  • A healthy worker effect may have biased the results.
  • Recent measurements may not reflect historical exposures or historical use of protective equipment.

Topics

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

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Cancer Registry, Standardized Incidence Ratio (SIR), confidence interval, Mesothelioma, Laryngeal Cancer, Carcinogenic.

Related studies

• Occupational exposures of firefighting and urinary tract cancer risk among men in the Norwegian Fire Departments Cohort — N. Marjerrison, T.K. Grimsrud, et al. (2023)
• Cancer incidence among firefighters: 45 years of follow-up in five Nordic countries — E. Pukkala, J.I. Martinsen, et al. (2014)
• Comparison of cancer incidence and mortality in the Norwegian Fire Departments Cohort, 1960-2018 — N. Marjerrison, J. Jakobsen, et al. (2022)
• Cancer Incidence and Mortality among Firefighters: An Overview of Epidemiologic Systematic Reviews — E. Laroche, S. L'Espérance (2021)
• Cancer risk among firefighters and police in the Ontario workforce — J. Sritharan, T.L. Kirkham, et al. (2022)
• Mortality of older construction and craft workers employed at department of energy (DOE) nuclear sites: follow-up through 2011 — K. Ringen, J. Dement, et al. (2015)

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