Cancer incidence among firefighters: 45 years of follow-up in five Nordic countries

Our plain-English summary of Cancer incidence among firefighters: 45 years of follow-up in five Nordic countries, by E. Pukkala, J.I. Martinsen, E. Weiderpass, et al (Occupational and Environmental Medicine, 2014).

The study

• Authors: E. Pukkala, J.I. Martinsen, E. Weiderpass, K. Kjaerheim, E. Lynge, L. Tryggvadottir, P. Sparén, P.A. Demers
• Journal: Occupational and Environmental Medicine
• Published: 2014;71(6):398-404
• Cited by: 118 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Firefighters are potentially exposed to a wide range of known and suspected carcinogens through their work. The objectives of this study were to examine the patterns of cancer among Nordic firefighters, and to compare them with the results from previous studies.

Methods: Data for this study were drawn from a linkage between the census data for 15 million people from the five Nordic countries and their cancer registries for the period 1961-2005. SIR analyses were conducted with the cancer incidence rates for the entire national study populations used as reference rates.

Results: A total of 16 422 male firefighters were included in the final cohort. A moderate excess risk was seen for all cancer sites combined, (SIR=1.06, 95% CI 1.02 to 1.11). There were statistically significant excesses in the age category of 30-49 years in prostate cancer (SIR=2.59, 95% CI 1.34 to 4.52) and skin melanoma (SIR=1.62, 95% CI 1.14 to 2.23), while there was almost no excess in the older ages. By contrast, an increased risk, mainly in ages of 70 years and higher, was observed for non-melanoma skin cancer (SIR=1.40, 95% CI 1.10 to 1.76), multiple myeloma (SIR=1.69, 95% CI 1.08 to 2.51), adenocarcinoma of the lung (SIR=1.90, 95% CI 1.34 to 2.62), and mesothelioma (SIR=2.59, 95% CI 1.24 to 4.77). By contrast with earlier studies, the incidence of testicular cancer was decreased (SIR=0.51, 95% CI 0.23 to 0.98).

Conclusions: Some of these associations have been observed previously, and potential exposure to polycyclic aromatic hydrocarbons, asbestos and shift work involving disruption of circadian rhythms may partly explain these results.

In plain English

Linking census and cancer registry records from Denmark, Finland, Iceland, Norway and Sweden, the study followed 16 422 male professional firefighters for cancer from 1961 to 2005 and compared them with national male rates. Of 2653 cancers observed, 117 non-melanoma skin cancers were excluded from the "all cancers" category, which held 2536 cases against 2392 expected (SIR 1.06, 95% CI 1.02 to 1.11). The 17 mesotheliomas, a single category, showed a non-significant excess overall (SIR 1.55, 95% CI 0.90 to 2.48). At ages 70 and over, 10 cases gave a significant excess (SIR 2.59, 95% CI 1.24 to 4.77). Prostate cancer was raised at ages 30 to 49 (SIR 2.59, 95% CI 1.34 to 4.52). Lung adenocarcinoma and multiple myeloma were raised at ages 70 and over. Testicular cancer was below expected, with nine cases against 17.6 (SIR 0.51, 95% CI 0.23 to 0.98). It lacked data on work duration or exposure and could do little to control confounding. The authors concluded that potential exposure to polycyclic aromatic hydrocarbons, asbestos and shift work may partly explain the results.

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. Census records were linked to national cancer registries, and observed cancers were compared with those expected from national male rates (standardised incidence ratios, SIR).
• Who was studied: 16 422 male firefighters (412 991 person-years) in Sweden (8144), Finland (4740), Norway (2579), Denmark (760) and Iceland (199). They were aged 30 to 64 at censuses held between 1960 and 1990 and were followed for cancer from 1961 to 2005. Female firefighters were excluded because there were too few.
• Exposure: Being recorded in a census as a professional firefighter (working as one for more than half the regular working hours in the census year). Office and other non-firefighting fire-department staff were not counted. No individual measures of asbestos or other exposures were available, and no fiber types were studied.
• Main results:
  • 2653 cancer cases were observed among the firefighters. 117 non-melanoma skin cancers were excluded from the 'all cancers' category, leaving 2536 observed versus 2392 expected (SIR=1.06, 95% CI 1.02 to 1.11).
  • Mesothelioma, all ages: 17 cases, SIR 1.55 (95% CI 0.90 to 2.48), not statistically significant.
  • Mesothelioma by age at follow-up: 1 case at ages 30 to 49 (SIR 1.02, 95% CI 0.03 to 5.69); 6 cases at ages 50 to 69 (SIR 0.98, 95% CI 0.36 to 2.13); 10 cases at ages 70 and over (SIR 2.59, 95% CI 1.24 to 4.77).
  • No mesothelioma cases were observed among the firefighters before 1976.
  • Prostate cancer at ages 30 to 49: 12 cases, SIR 2.59 (95% CI 1.34 to 4.52). Prostate cancer at all ages: SIR 1.13 (95% CI 1.05 to 1.22).
  • Lung cancer overall was not raised (310 cases, SIR 0.97, 95% CI 0.87 to 1.09). Lung adenocarcinoma was raised at all ages (SIR 1.29, 95% CI 1.02 to 1.60) and at ages 70 and over (37 cases, SIR 1.90, 95% CI 1.34 to 2.62).
  • Multiple myeloma at ages 70 and over: 24 cases, SIR 1.69 (95% CI 1.08 to 2.51).
  • Testicular cancer was lower than expected: 9 observed versus 17.6 expected (SIR=0.51, 95% CI 0.23 to 0.98).
• The authors' conclusion: The authors concluded that some of the associations had been observed before, and that potential exposure to polycyclic aromatic hydrocarbons, asbestos and shift work disrupting circadian rhythms may partly explain the results.
• Limitations the authors state:
  • No information was available on duration of employment or other characteristics of exposure.
  • The ability to control for confounding, such as lifestyle factors, was very limited.
  • Occupation was taken from a census at one point in time and may not reflect a person's lifelong work history. The authors judged the resulting dilution to be small.
  • Case numbers in each country were small, so only very large differences between countries could have been detected.
  • Firefighters probably represent a population selected for general health.

Topics

Medical terms in this study, explained in our Lexicon: Incidence, Myeloma, Adenocarcinoma, Mesothelioma.

Related studies

• Cancer incidence among seafarers and fishermen in the Nordic countries — K. Ugelvig Petersen, E. Pukkala, et al. (2020)
• Occupation and risk of cancer of the renal pelvis in Nordic countries — I.M. Michalek, J.I. Martinsen, et al. (2019)
• Firefighters and cancer: where are we and where to now? — L. Fritschi, D.C. Glass (2014)
• Heavy metals, welding fumes, and other occupational exposures, and the risk of kidney cancer: A population-based nested case-control study in three Nordic countries — I.M. Michalek, J.I. Martinsen, et al. (2019)
• Occupational exposures and male breast cancer: A nested case-control study in the Nordic countries — M. Talibov, J. Hansen, et al. (2019)
• The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping beta-carotene and retinol supplements — G.E. Goodman, M.D. Thornquist, et al. (2004)

Browse more research in Occupational and Environmental Medicine, or return to medical research.