Acute and chronic inflammation in firefighters: A narrative review

In 2022, an International Agency for Research on Cancer (IARC) Monographs Working Group assessed the carcinogenic hazard of occupational exposure as a firefighter. The working group concluded that occupational exposure as a firefighter is carcinogenic to humans and identified chronic inflammation as a contributing factor. This review therefore aimed to summarise the evidence of acute and chronic inflammation in firefighters. Acute and chronic (>2-6 weeks) levels inflammatory markers (Eg. Interleukin (IL) 1β, IL-6, IL-8, IL-10, tumor necrosis factor alpha (TNFα), C reactive protein (CRP)) were examined in firefighters following exposure to typical firefighting duties including structural and wildland fires. Experimental studies without exposure to combustion emissions were also reviewed to examine the specific contribution of heat exposure, physical exertion, cognitive load and restricted sleep to inflammation in firefighters. For chronic inflammation, the strongest evidence existed for elevated circulating IL-6 (n = 5 studies), followed by elevated IL-1β (n = 3), CRP (n = 3) and IL-8 (n = 2). Acute elevations in IL-6 (n = 8 studies), IL-8 (n = 7) and IL-1β (n=4) were also evident in firefighters in the hours and days following exposure to structural and wildland fires. Experimental studies provided evidence that physical exercise and heat contribute to acute elevations in IL-6 (n = 6) and TNFα (n = 3). In summary, the data reviewed provide strong support that typical firefighting duties can induce both acute and chronic inflammation. More work is needed to determine the prevalence of inflammation in firefighters and to identify mitigating strategies to lower the risk of firefighters developing inflammatory related-chronic disease.