Assessment of exposure to fine and ultrafine particulate-bound polycyclic aromatic hydrocarbons during prescribed burns

Portugal is one of the most affected countries in southern Europe by wildfires. The human exposure characterization to fine particulate matter (PM) during fires remains limited; no information is available for ultrafine particles nor their composition on polycyclic aromatic hydrocarbons (PAHs). This work assesses fine and ultrafine PM levels and their composition on 18 PAHs during two prescribed burns performed in Porto (North of Portugal). A low-pressure impactor was used to collect 14 PM fractions (PM15nm to PM10µm) at the firefighting area. Concentrations of PM were determined by gravimetry, and its PAHs content was determined with a microwave-assisted extraction and analyzed by liquid chromatography with fluorescence/UV-Vis detectors. Total cumulative concentrations of collected PM varied between 0.34 to 1.41 mg/m3 with fine (PM156nm to PM2.5µm) and ultrafine (PM15nm to PM95nm) PM accounting for 48.6-63.1% and 11.7-31.4% of total PM, respectively. Benzo(a)pyrene, carcinogenic PAH, was detected in all PM fractions with values ranging from 5.72×10-5 to 2.63×10-3 µg/m3. The PM-bound possible or probable carcinogenic PAHs represented up to 7.62% of total PAHs. Further studies concerning humans, e.g., firefighting forces and local population exposure to fine/ultrafine PM and PAHs are urgently needed to pursue preventive measures to promote human health.