Authors' objectives: To determine whether there is any new evidence to support a causal association between colon cancer and firefighting.

Authors' results and conclusions: The risk of cancer in firefighters is explored using observational studies (i.e., cohort, case-control). There are also systematic reviews and meta-analyses on the topic. It is difficult to find studies solely on ‘colon cancer’ in firefighters. Most often, multiple cancers are studied concurrently, using the same dataset, or study population. Even though there are many studies on cancer risk among firefighters, findings are inconsistent. These inconsistent risk estimates are due to multiple factors affecting the level of exposure, varying study populations, age range, duration of employment, availability/quality of fire extinguishing materials, protective gear and usage of PPE. Existence of confounding factors and biases such as healthy worker effect (HWE), smoking history, night shiftwork, UV radiation exposure, and medical surveillance bias. Despite the inconsistent results in the literature, overall inference for several cancers indicates an elevated cancer risk due to firefighting as an occupation. The literature highlights skin melanoma, thyroid, and prostate cancers. In terms of colon cancer, the results are mixed displaying both increased and decreased estimates or no association. Occupational exposures in firefighting are complex and estimating cancer risk can be difficult. Major challenges exist regarding the quality of exposure assessment, confounding and medical surveillance bias. Consistent case and exposure definitions, larger sample sizes, and longer follow-up periods across studies may help when the risk for a rare disease (cancer) is estimated. Even though the IARC Monograph Volume 132 concludes as “Occupational exposure as a firefighter is carcinogenic to humans”, they include colon cancer among the five cancers with “limited evidence”. With regards to colon cancer, the IARC Working Group noted that “a positive association was seen between occupational exposure as a firefighter and colon cancer; however, chance, bias, and confounding could not be ruled out with reasonable confidence”. Similar to prostate cancer, surveillance bias was the main concern for colon cancer, as the studies of mortality displayed reduced or null associations compared to the studies of incidence displaying positive associations. Of the six studies selected for this review, three pointed to increased risk of colon cancer in firefighters, and the other three pointed to nonsignificant associations. Where 13 Colon Cancer and Firefighting October 2024 mortality data was available, the risk estimates either became not significant or changed direction (i.e., decreased risk). We conclude that the current level of evidence regarding the risk of colon cancer from firefighting remains limited. It is important to collect both incidence and mortality data for all firefighters, and to improve the methodological quality of studies through more accurate exposure and outcome data collection, larger study populations, longer follow up periods, and addressing inherent confounding factors and biases. Regardless of the establishment of a definitive causal link between colon cancer and firefighting, efforts to enhance surveillance and implement primary prevention measures should continue.

Authors' methods: A comprehensive and systematic literature search was conducted on August 13, 2024. The search was done on commercial medical literature where a combination of keywords was employed in this search. No limitation, such as on the date or language of publication was implemented in any of these searches. A manual search was also planned and conducted on the references of the articles that were retrieved in full. Inclusion criteria were published studies in peer-reviewed journals from 2020 onwards, exploring relationships between firefighting and cancer, investigating the causal path, comparing cancer incidence and mortality rates in firefighters and the general population and were cohort or case control studies with sound methodological quality. Exclusion criteria excluded studies which examined groups other than firefighters, firefighters with illnesses other than cancer, observational studies with no comparison groups, and studies with low methodological quality. In addition, there are methodological challenges due to high heterogeneity across studies.

Project Status: Completed

URL for project: https://www.worksafebc.com/en/about-us/research-services/evidence-based-medicine-and-systematic-reviews

Year Published: 2024

URL for published report: https://www.worksafebc.com/en/resources/health-care-providers/guides/colon-cancer-firefighting?lang=en

English language abstract: An English language summary is available

Publication Type: Mini HTA

Country: Canada

Organisation Name: WorkSafeBC

Contact Address: 6591 Westminster Highway, Richmond, BC, V7C 1C6 Canada. Tel: 604-231-8417; Fax: 604-279-7698

Contact Name: ebpg@worksafebc.com

Contact Email: ebpg@worksafebc.com

Copyright: WorkSafe BC