Carcinogenicity of occupational exposure as a firefighter. [Video]

Opening:
Welcome to our educational video on the carcinogenicity of occupational exposure as a firefighter. In June 2022, 25 scientists from eight countries met at the International Agency for Research on Cancer (IARC) in Lyon, France, to finalize their evaluation of the carcinogenicity of occupational exposure as a firefighter. This assessment will be published in Volume 132 of the IARC Monographs.

Firefighter Exposure and Risks:
Occupational exposure as a firefighter was classified as ‘carcinogenic to humans’ (Group 1) based on sufficient evidence for cancer in humans. The Working Group concluded that there was sufficient evidence in humans for mesothelioma and bladder cancer. There was limited evidence in humans for colon, prostate, and testicular cancers, and for melanoma and non-Hodgkin lymphoma. There was also strong mechanistic evidence that occupational exposure as a firefighter shows the following key characteristics of carcinogens in exposed humans: is genotoxic, induces epigenetic alterations, induces oxidative stress, induces chronic inflammation, and modulates receptor-mediated effects.

Hazards and Exposures: “Firefighters can be exposed to combustion products from fires, such as polycyclic aromatic hydrocarbons (PAHs) and particulates, asbestos from building materials, chemicals in firefighting foams, flame retardants, diesel exhaust, and other hazards including night shift work and ultraviolet radiation. Uptake of fire effluents or other chemicals can occur via inhalation and dermal absorption and possibly via ingestion.

Epidemiological Studies:
Since the previous classification of firefighting as ‘possibly carcinogenic to humans’ (Group 2B) by the IARC Monographs in 2007, many new studies have investigated the association between occupational exposure as a firefighter and cancer risk in humans. The Working Group conducted a meta-analysis incorporating cohort studies of firefighters published up to June 2022. More than 30 non-overlapping cohort studies following firefighters for cancer over time were considered most informative for the evaluation and were conducted in Asia, Europe, North America, and Oceania.

Findings and Evidence:
On the basis of the available epidemiological evidence, the Working Group concluded that a causal association exists between occupational exposure as a firefighter and mesothelioma and bladder cancer. The Group also found credible positive associations for colon, prostate, and testicular cancers, melanoma, and non-Hodgkin lymphoma. However, bias from greater medical surveillance and detection in firefighters, or confounding by physical and lifestyle characteristics, could not be reasonably excluded as explanations for these positive findings.

Mechanistic Evidence:
Consistent and coherent evidence of genotoxic effects was observed in firefighters, including increases in PAH-DNA adducts in blood, urinary mutagenicity, DNA damage in blood, and micronucleus frequency in buccal cells. Evidence of epigenetic effects, oxidative stress, and chronic inflammation was also found. Declines in lung function associated with changes in inflammatory markers and exposure-associated bronchial hyperreactivity were reported in firefighters.

Summary and Recommendations:
The IARC’s evaluation indicates that occupational exposure as a firefighter poses significant carcinogenic risks. It is crucial to implement protective measures and reduce exposure to these hazards. Thank you for watching. Remember, awareness and prevention are key to protecting our firefighters.