In vitro toxicological assessment of ultrafine particle emissions (UFP) from a domestic pellet stove using softwood-fir and hardwood-beech

The TOBICUP (TOxicity of BIomass COmbustion generated Ultrafine Particles) project was designed to gain deeper insight on the possible health effects of ultrafine particulate matter (UFP, dp) The present study shows only preliminary data regarding the in vitro toxicological evaluation of UPF samples provided by the Energy and Environment Laboratory of Piacenza (Italy) (LEAP). The combustion experiments were conducted on a commercially available 11 kW top-feed wood pellet stove without water heat exchanger, with fan assisted flue discharge and internal fuel hopper. The 3–4 h combustion cycles were designed to represent real-life usage of the combustion appliance. The stove was operated by modulating the heat output between the maximum and minimum loads. Two types of wood pellets (softwood-fir and hardwood-beech) were used. UFP sampling was performed in parallel using three multistage cascade impactors, considering only particles collected on stages with nominal cut-off lower than 100 nm. Different supports (polycarbonate, quartz fibre filters and aluminium foils) were used to ensure the possibility to perform the full chemical characterization and toxicological analyses. A549 cells (lung epithelial cells) were treated with UFP samples at 25–100 μg/ml concentrations for 24 h and with DEP (25–100 μg/ml). We evaluated 1) viability (MTT test) 2) DNA damage (alkaline comet assay and γ-H2AX) 3) intracellular ROS (oxygen radicals) and RNS (nitrogen radicals) production. The UPF intracellular disposition will be evaluated by transmission electron microscopy analysis. The results show, by two predictive tests, DNA damage as single (SB) and double breaks (DB) that do not seem to correlate with radical species production. This project is funded by Fondazione Cariplo (Project TOBICUP – Ref. 2013-1040).