Cancer risk among firefighters and police in the Ontario workforce

Our plain-English summary of Cancer risk among firefighters and police in the Ontario workforce, by J. Sritharan, T.L. Kirkham, J. MacLeod, et al (Occupational and Environmental Medicine, 2022).

The study

• Authors: J. Sritharan, T.L. Kirkham, J. MacLeod, N. Marjerrison, A. Lau, M. Dakouo, C. Logar-Henderson, T. Norzin, N.L. DeBono, P.A. Demers
• Journal: Occupational and Environmental Medicine
• Published: 2022;79(8):533-539
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Firefighters and police often work in high-stress, complex environments with known and suspected carcinogenic exposures. We aimed to characterise cancer incidence among firefighters and police.

Methods: The Occupational Disease Surveillance System (ODSS) was used to identify workers employed as firefighters or police in Ontario. A cohort of workers were identified using lost-time workers' compensation claims data and followed for cancer in the Ontario Cancer Registry (1983-2020). Cox proportional hazard models were used to estimate HRs and 95% CIs for primary site-specific cancer diagnoses adjusted for age at start of follow-up, birth year and sex.

Results: A total of 13 642 firefighters and 22 595 police were identified in the cohort. Compared with all other workers in the ODSS, firefighters and police had increased risk of prostate cancer (firefighters: HR=1.43, 95% CI 1.31 to 1.57; police: HR=1.47, 95% CI 1.35 to 1.59), colon cancer (firefighters: HR=1.39, 95% CI 1.19 to 1.63; police: HR=1.39, 95% CI 1.21 to 1.60) and skin melanoma (firefighters: HR=2.38, 95% CI 1.99 to 2.84; police: HR=2.27, 95% CI 1.96 to 2.62). Firefighters also had increased risk of cancer of the pancreas, testis and kidney, as well as non-Hodgkin's lymphoma and leukaemia. Police had increased risk of thyroid, bladder and female breast cancer. When compared directly with the police, firefighters had an elevated risk of mesothelioma and testicular cancer.

Conclusions: Firefighters and police demonstrated some similar as well as some unique cancer risks. Findings from this larger worker population may have important implications for workplace and policy-level changes to improve preventative measures and reduce potential exposures to known carcinogenic hazards.

© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

In plain English

This study used Ontario's Occupational Disease Surveillance System, which links accepted lost-time workers' compensation claims to health records. It identified 13,642 firefighters and 22,595 police officers and detectives from the job title on their claim, and followed them for new cancer diagnoses in the Ontario Cancer Registry from 1983 to 2020. Compared with all other workers in the system, both groups had higher rates of any cancer, prostate cancer, colon cancer and skin melanoma. Firefighters also had higher rates of pancreatic, kidney and testicular cancer, non-Hodgkin's lymphoma and leukaemia. Police had higher rates of thyroid, bladder and female breast cancer. Both groups had lower rates of lung cancer. For mesothelioma, firefighters had 11 cases and a hazard ratio of 1.56 (95% CI 0.86 to 2.84) against all other workers, which was not statistically significant. Compared directly with police, the firefighters' hazard ratio was 3.21 (95% CI 1.01 to 10.20). Asbestos exposure was not measured. The authors suggested firefighters are exposed to asbestos fibres from burning older buildings. The study had no data on smoking or length of employment.

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 built from linked administrative data (workers' compensation claims linked to a cancer registry), analysed with Cox proportional hazards models adjusted for age at start of follow-up, birth year and sex
• Who was studied: 13,642 firefighters and 22,595 police officers and detectives, within a cohort of 2,368,226 Ontario, Canada workers with accepted lost-time compensation claims (claims from 1983 to 2019), followed for cancer to the end of 2020. Firefighters were 96% male and police 83% male.
• Exposure: Occupation as firefighter or police officer/detective, taken from the job code on the compensation claim. No asbestos or other exposure measurements were made. Asbestos is discussed by the authors only as a possible explanation for the mesothelioma finding.
• Main results:
  • Compared with all other workers, both firefighters and police had statistically significant increased risk of any cancer (firefighters: 1730 cases, HR 1.23, 95% CI 1.17 to 1.29; police: 2377 cases, HR 1.17, 95% CI 1.13 to 1.22), prostate cancer, colon cancer and skin melanoma.
  • Prostate cancer compared with all other workers: firefighters HR 1.43 (95% CI 1.31 to 1.57); police HR 1.47 (95% CI 1.35 to 1.59).
  • Skin melanoma compared with all other workers: firefighters HR 2.38 (95% CI 1.99 to 2.84); police HR 2.27 (95% CI 1.96 to 2.62).
  • Firefighters, compared with all other workers, also had statistically significant increased risk of pancreatic cancer (HR 1.34, 95% CI 1.02 to 1.76), kidney cancer (HR 1.52, 95% CI 1.24 to 1.87), testicular cancer (HR 2.56, 95% CI 1.78 to 3.68), non-Hodgkin's lymphoma (HR 1.35, 95% CI 1.11 to 1.64) and leukaemia (HR 1.35, 95% CI 1.05 to 1.73).
  • Police, compared with all other workers, had statistically significant increased risk of thyroid cancer (HR 1.35, 95% CI 1.07 to 1.70), bladder cancer (HR 1.25, 95% CI 1.07 to 1.45) and female breast cancer (HR 1.26, 95% CI 1.01 to 1.57).
  • Both groups had statistically significant reduced risk of lung cancer compared with all other workers (firefighters HR 0.84, 95% CI 0.74 to 0.97; police HR 0.71, 95% CI 0.62 to 0.80). Police also had reduced risk of laryngeal cancer (HR 0.61, 95% CI 0.39 to 0.97).
  • Mesothelioma compared with all other workers: firefighters had 11 cases, HR 1.56 (95% CI 0.86 to 2.84), not statistically significant. Police had fewer than 6 cases, too few to report.
  • Firefighters compared directly with police had statistically significant increased risk of mesothelioma (HR 3.21, 95% CI 1.01 to 10.20) and testicular cancer (HR 1.96, 95% CI 1.19 to 3.23).
  • Excluding the 273 workers who had worked in both firefighting and policing did not significantly change the findings. Restricting the analysis to men left the findings unchanged.
• The authors' conclusion: The authors concluded that firefighters and police showed some similar and some unique cancer risks. Many associations weakened when the two groups were compared with each other, which the authors suggested may point to common exposures. For mesothelioma, the authors suggested that police may be less likely than other workers to be exposed to asbestos. They also suggested that firefighters are exposed to asbestos fibres from burning older buildings. The authors called for further investigation of exposures in these occupations.
• Limitations the authors state:
  • Job information came from a single point in time (the job title on the claim), so changes in jobs and duration of employment could not be assessed. The authors note this can cause misclassification.
  • No exposure measurements or exposure surrogates were used, so exposure levels could not be evaluated.
  • There was no information on smoking, ethnicity or screening behaviours to control for confounding.
  • A healthy worker effect may have influenced findings because of the strict fitness requirements for entry into these jobs.
  • The study made many comparisons, which can produce chance findings.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Occupational Disease, Cancer Registry, Colorectal Cancer, Mesothelioma.

Related studies

• Cancer incidence among firefighters: 45 years of follow-up in five Nordic countries — E. Pukkala, J.I. Martinsen, et al. (2014)
• Cancer incidence in sites potentially related to occupational exposures: 58 years of follow-up of firefighters in the Norwegian Fire Departments Cohort — 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)
• Firefighters and cancer: where are we and where to now? — L. Fritschi, D.C. Glass (2014)
• Incidence of mesothelioma and asbestosis by occupation in a diverse workforce — N.L. DeBono, H. Warden, et al. (2021)
• 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)

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