Human exposure to polycyclic aromatic hydrocarbons during structure fires: Concentrations outside and inside self-contained breathing apparatus and in vitro respiratory toxicity

Structure fires release several health-hazardous compounds, including polycyclic aromatic hydrocarbons (PAHs), and the use of self-contained breathing apparatus (SCBA) is mandatory to protect firefighters' airways. The characterization of PAHs released during structure fires is scarce, principally in European countries. This work elucidates the mechanisms of toxic effects associated with human exposure to PAHs released during structure fires, by assessing for the first time, the levels in the breathable air of sapper firefighters with and without the use of SCBA. An in vitro co-culture model of air-blood barrier was used to evaluate respiratory toxicity. Concentrations of total PAHs (∑PAHs) inside the burning structure were 8.20-19.8 times higher than the values monitored inside fire stations (11.5-28.0 μg/m³versus 1.41 μg/m³; p < 0.005) and 2688-5872 times higher than the levels detected inside the SCBA used during the fire events. Levels of carcinogenic PAHs were 6.90-20.5 times higher than observed for the control group (p ≤ 0.005). Inside to outside ratios (<1) suggested the contribution of PAHs from fires to the levels detected inside the protection system. Exposure to fire emissions increased the risk of lung cancer. The use of SCBA system substantially reduced exposure to PAHs, still levels detected outside/inside the SCBA facemask significantly reduced the viability of alveolar and bronchial cell lines (<70 %). Benzo(a)pyrene (100 %), naphthalene and phenanthrene (97.5 %), benzo(b+j)fluoranthene (90 %), and fluorene (87.5 %) found inside the SCBA mask were able to permeate the co-culture model of air-blood barrier. More studies need to corroborate these preliminary findings and evaluate the synergic effect of fire effluent complex mixtures and their contribution to respiratory toxicity.