Impact of wildfire emissions exposure on the associations between levels of lung injury, lipid peroxidation, DNA oxidation, and exposure biomarkers

Firefighters face increased risks of developing cardio-respiratory diseases and cancer. This study aimed, for the first time, to simultaneously characterize several biomarkers of effect (lung injury by Clara cell 16 -CC16, lipid peroxidation by 8-isoprostane-8-iso, and DNA oxidation by 8-hydroxy-2-deoxyguanosine-8-OHdG) and exposure (polycyclic aromatic hydrocarbons metabolites - 6 OHPAHs and 17 metal(loid)s) in (pre- and post-exposure) paired urine samples of wildland firefighters, while exploring their inter-/intra-associations and accounting for tobacco consumption. Wildfire combat influenced the levels of CC16 (+39 %), 8-iso (+33 %), 8-OHdG (-13 to +19 %), individual and sum of OHPAHs (+75-211 %), and metal(loid)s (up to 43 %, p > 0.05: lithium, zinc, antimony, and lead); post-exposure increments were more evident among non-smokers. Post-exposure (individual and sum) OHPAHs and some metal(loid)s (copper, cadmium, barium, antimony, copper, lead, zinc, selenium, and rubidium) were positively associated with CC16, 8-iso and/or 8-OHdG (0.609 < r < 0.838; 0.001 < p < 0.047). Spearman's correlations and principal component analysis highlighted CC16 as the best discriminant effect biomarker of wildland firefighting, correlating positively with individual and sum of OHPAHs, cadmium, barium and copper (0.647 < r < 0.764; 0.006 < p < 0.031). Cumulative exposure to wildfires and tobacco contributed to positive correlations (0.587 < r < 0.715; 0.009 < p < 0.045) between lipid peroxidation and arsenic, antimony, lead, and copper, and between DNA oxidation and lead. Smoking firefighters presented higher OHPAHs baseline concentrations (2- to 14-fold), and lung injury and DNA oxidation induced by cadmium, copper, strontium, cesium, barium and thallium (0.661 < r < 0.709; 0.022 < p < 0.038). Given firefighter's carcinogenic risks, performing similar studies in larger groups is crucial to enhance risk assessment by establishing a well-defined panel of effect and exposure biomarkers.