Cytotoxic and genotoxic responses of human lung cells to combustion smoke particles of Miscanthus straw, softwood and beech wood chips.

Inhalation of particulate matter (PM) from residential biomass combustion is epidemiologically associated with cardiovascular and pulmonary diseases. This study investigates PM emissions from combustion of commercial Miscanthus straw (MS), softwood chips (SWC) and beech wood chips (BWC) in a domestic-scale boiler (40 kW). The PM emitted during combustion of the MS, SWC and BWC were characterized by ICP-MS/OES, XRD, SEM, TEM, and DLS. Cytotoxicity and genotoxicity in human alveolar epithelial A549 and human bronchial epithelial BEAS-2B cells were assessed by the WST-1 assay and the DNA-Alkaline Unwinding Assay (DAUA). PM uptake/translocation in cells was investigated with a new method developed using a confocal reflection microscope. SWC and BWC had a inherently higher residual water content than MS. The PM emitted during combustion of SWC and BWC exhibited higher levels of Polycyclic Aromatic Hydrocarbons (PAHs), a greater variety of mineral species and a higher heavy metal content than PM from MS combustion. Exposure to PM from combustion of SWC and BWC induced cytotoxic and genotoxic effects in human alveolar and bronchial cells, whereby the strongest effect was observed for BWC and was comparable to that caused by diesel PM (SRM 2 975), In contrast, PM from MS combustion did not induce cellular responses in the studied lung cells. A high PAH content in PM emissions seems to be a reliable chemical marker of both combustion efficiency and particle toxicity. Residual biomass water content strongly affects particulate emissions and their toxic potential. Therefore, to minimize the harmful effects of fine PM on health, improvement of combustion efficiency (aiming to reduce the presence of incomplete combustion products bound to PM) and application of fly ash capture technology, as well as use of novel biomass fuels like Miscanthus straw is recommended.