Firefighters: occupational exposure recognized as carcinogenic for mesothelioma and bladder cancer

Firefighters: occupational exposure recognized as carcinogenic for mesothelioma and bladder cancer

Occupational exposure from firefighters is now classified as a carcinogen (group 1) by the International Agency for Research on Cancer (IARC). This is the conclusion of a monograph prepared in June by 25 scientists from 8 countries that will be published in 2023 and whose main results have been published in “The Lancet Oncology”.

The IARC concludes that there is a cause and effect relationship between occupational exposure as a firefighter and mesothelioma and bladder cancer, considering the evidence “sufficient”. In contrast, for cancers of the colon, prostate, testicles, melanoma and non-Hodgkin’s lymphoma, the UN agency considers the data to be limited.

Regarding the mechanism, the evidence is considered strong, since 5 of the 10 key characteristics are found: genotoxicity, epigenetic alterations, oxidative stress, chronic inflammation, receptor-mediated effects.

Numerous publications since 2007

Until then, the activity of firefighters was evaluated as possibly carcinogenic (group 2B) in the 2007 monograph. Since then, several studies have been published, in particular after the 2001 World Trade Center attack (in 2018 and in 2021) . The experts drew on a total of 52 cohort and case-control studies, 12 case reports, and 7 meta-analyses.

For mesothelioma, the risk was estimated to be 58% higher for firefighters compared to the general population, with asbestos being a likely causative agent. The estimate was slightly heterogeneous across studies. For bladder cancer, positive associations with incidence were seen in several firefighter cohorts compared to the general population. The estimated risk increase was small in magnitude (16%), but was statistically precise and with low heterogeneity », it is detailed. Also, while smoking is less common among firefighters with a lower risk of lung cancer, the association with bladder cancer is likely underestimated compared with the general population, he adds.

For the other cancers studied, if credible positive associations have been observed, the methodological biases of the studies do not allow us to conclude, the authors citing, among other things, the surveillance bias for cancers that are often indolent, such as prostate cancer. .

A mixture of multiple carcinogens.

Occupational exposure as a firefighter is complex and includes a variety of risks from fires and other events., You are reminded. The experts underline the heterogeneity that covers the activity of firefighters, whether in the exercise environment (industrial context, urban, natural environment, areas most affected by climate change), in the type of intervention (building fires, vehicles, woods or events such as traffic accidents, building collapse) or in the mode of activity (volunteers or employees, part-time or full-time).

Thus, firefighters are exposed to a complex mixture of combustion products (polycyclic aromatic hydrocarbons, volatile organic compounds, metals, particles), diesel gases, construction materials (asbestos) and other risks (thermal shock, shift work, UV and other punishments). ). Not to mention flame retardants used for textiles and persistent organic pollutants. Several of these agents are already classified as carcinogens in groups 1, 2A and 2B.

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