Firefighter exposure to airborne benzene: a systematic review of measured levels, toxicological significance, methodological challenges, and research gaps.

Firefighting is a hazardous occupation that entails short-term, high-level exposure to a complex mixture of combustion products, among which benzene is of special concern due to its known carcinogenicity. The purpose of this systematic review was to evaluate the complexity and variability of exposure of firefighters to airborne benzene and its toxicological relevance during active fire suppression and overhaul duties in wildland, structural, and training environments. Based on the PRISMA 2020 guidelines, a literature search was conducted using PubMed, Scopus, and Web of Science for studies reporting direct air sampling of benzene in firefighting settings. A total of 32 studies were included, and a structured, domain-based approach was conducted to assess study quality and risk of bias. Although this review summarizes measured concentrations, it is also the first to provide an evidence-based critique of the methodological deficiencies in this body of literature. Benzene concentrations exceeded occupational limits in all scenarios, with medians as high as 40.3 ppm during structural fire attacks and with maximum values exceeding 300 ppm. Results indicate that it is impossible to correlate external concentrations to actual internal dose reliably. This is primarily due to a lack of consideration of non-inhalation exposure routes (e.g., vapor penetration into gear, off-gassing, and post-fire contamination), as well as the large variation in individual exposures driven by work practices and personal choices, which is masked by pooled environmental data. The recommendations provided herein offer a roadmap for improving the accuracy and relevance of future exposure research in the firefighting profession.