Cancer Incidence and Mortality among Firefighters: An Overview of Epidemiologic Systematic Reviews

Our plain-English summary of Cancer Incidence and Mortality among Firefighters: An Overview of Epidemiologic Systematic Reviews, by E. Laroche, S. L'Espérance (International Journal of Environmental Research and Public Health, 2021).

The study

• Authors: E. Laroche, S. L'Espérance
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;18(5)
• Type of article: Systematic review
• Cited by: 39 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Firefighters are exposed to carcinogens that may increase their risk of developing many types of occupational cancer. Many systematic reviews (SRs) have been produced with sometimes conflicting conclusions. In this overview of reviews, we aim to assess the conclusion consistency across the available systematic reviews on the cancer risk in firefighters. Literature searches were conducted in several indexed databases and grey literature to retrieve systematic reviews aiming to evaluate cancer incidence or cancer mortality in firefighters. Results from included SRs were analyzed according to the tumour site. Out of 1054 records identified by the search in the databases, a total of 11 SRs were ultimately included. The original studies (n = 104) analyzed in the SRs were published between 1959 and 2018. The results consistently reported a significant increase in the incidence of rectal, prostate, bladder and testicular cancers as well as mesothelioma and malignant melanoma in firefighters compared to the general population. The SRs also indicate that death rates from rectal cancer and non-Hodgkin's lymphoma are higher among firefighters. Consistent SR results suggest that several types of cancer may be more frequent in firefighters than in the general population.

In plain English

This article was an overview of earlier systematic reviews, not a new study of firefighters. The authors searched databases up to October 2019 and grey literature. They included 11 systematic reviews covering 104 publications from 1959 to 2018, mostly cohort and case-control studies. They compared the reviews' results by cancer site without pooling them. Overall cancer incidence did not differ significantly from reference populations. For mesothelioma, one review (Jalilian et al., 5 studies) reported significantly higher incidence (SIR 1.60, 95% confidence interval 1.09 to 2.34). Guidotti's review, without pooled numbers, judged that the evidence strongly favored mesothelioma being an occupational disease of firefighters. The IRSST review saw a possible strong association. Pooled estimates in four reviews showed no significant increase in lung cancer. The authors concluded that rectal, prostate, bladder and testicular cancers, mesothelioma and malignant melanoma were consistently reported as more frequent in firefighters, with higher death rates from rectal cancer and non-Hodgkin's lymphoma. They cautioned that the reviews were of low methodological quality and mostly concerned male firefighters. They mentioned asbestos in older buildings as a possible past exposure.

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: Overview of systematic reviews (review of reviews); results compared by cancer site, with no new meta-analysis
• Who was studied: 11 systematic reviews (from Canada, the United States, Australia, the United Kingdom, Iran and Europe, published 1990 to 2019). Together they included 104 publications on firefighters published between 1959 and 2018: 47 cohort, 39 case-control and 12 descriptive studies, plus five systematic reviews and one narrative review. The firefighters studied were mostly urban and mostly male.
• Exposure: Work as a firefighter, involving exposure to soot, polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds, acid gases and particulate matter. The discussion notes past asbestos exposure in buildings. No fiber type or dose was studied.
• Main results:
  • Overall cancer incidence in firefighters did not differ significantly from reference populations across reviews (SIR from 0.89 to 1.02)
  • Overall cancer mortality estimates in the reviews ranged from 0.92 to 1.09. Three reviews reported a significant increase of 4% to 9% in firefighters' standardized mortality.
  • Mesothelioma: the Jalilian et al. review (5 studies) reported a significantly increased incidence in firefighters compared with the general population, SIR 1.60 (95% CI 1.09 to 2.34)
  • Mesothelioma: the Guidotti review concluded that the weight of the evidence strongly favored mesothelioma being an occupational disease of firefighters
  • Mesothelioma: the IRSST review concluded that there may be a strong association between firefighting and mesothelioma incidence
  • Five reviews gave pooled respiratory-tract results, and these showed no significant increase in lung, mouth and pharyngeal, or laryngeal cancer incidence or mortality in firefighters. Lung cancer estimates came from four of these reviews (Howe and Burch, LeMaster et al., Crawford et al., Jalilian et al.).
  • Significant increases in non-Hodgkin's lymphoma mortality in firefighters were consistently reported in the reviews
  • Two reviews found a significant increase in melanoma incidence in firefighters
  • Risk of bias related to literature search methods was rated high or uncertain in most of the included reviews
• The authors' conclusion: The authors concluded that the incidence of rectal, prostate, bladder and testicular cancers, mesothelioma and malignant melanoma is consistently reported as significantly higher in firefighters than in the general population. They also concluded that death rates from rectal cancer and non-Hodgkin's lymphoma are higher. They added that caution is needed because of the low methodological quality of the reviews.
• Limitations the authors state:
  • The included systematic reviews were of low methodological quality
  • Most results concern male firefighters, so they cannot be generalized to female firefighters
  • Limiting inclusion to English or French reviews may have increased publication bias
  • There was no formal evaluation of publication bias
  • Because of heterogeneity, combining original studies in meta-analyses (as several reviews did) is methodologically questionable
  • Confounding factors, such as years of service, subjects' origin and baseline health, may have affected the results
  • The ROBIS quality tool may not be well suited to systematic reviews of epidemiological studies

Topics

Medical terms in this study, explained in our Lexicon: Systematic Review, Mesothelioma.

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