Micronucleus assay in buccal and urothelial epithelial cells of wildland firefighters exposed to wildfire smoke

Occupational exposure as a firefighter is classified as carcinogenic to humans. However, information on the biological effects of wildland firefighting remains limited. This study aimed to assess genotoxicity in a group of wildland firefighters and evaluate the contribution of total concentration of urinary hydroxylated polycyclic aromatic hydrocarbons (ΣOHPAHs) to selected endpoints. A group of 59 northern Portuguese wildland firefighters (mean age: 35.5 ± 9.0 years) was evaluated before and during the wildfire season. Sociodemographic, lifestyle, occupational-related information was collected via questionnaire. The micronucleus (MN) assay in buccal and urothelial cells was applied to paired samples to assess the association with exposure, as indicated by urinary ΣOHPAHs levels. The risk of MN formation in urothelial cells was over twofold higher during the wildfire season [Frequency Ratio (FR): 2.13, 95 % CI: 1.99-2.27, p = 0.01]. A 35 % increase in MN frequency in buccal cells was observed during the wildfire season (FR: 1.35, 95 % CI: 0.76-2.40, p > 0.05). Urinary ΣOHPAHs exhibited a significant positive association with MN‰ in urothelial cells (FR:1.04, 95 % CI: 1.01-1.08, p < 0.05). This study provides the first assessment of MN frequency in urothelial cells of wildland firefighters, offering novel evidence of genotoxic risks and potential long-term health impacts associated with wildland firefighting.

Highlights: - Micronucleus (MN) frequency is considered a potential early cancer risk biomarker. - MN assay in buccal and urothelial cells is minimally invasive. - MN‰ in firefighters’ urothelial cells were over 2x higher during wildfire season. - Urinary total OHPAHs significantly increased MN‰ in firefighters’ urothelial cells. - MN assay in urothelial cells may serve as a biomonitoring tool for firefighters.