The use of biofuels in vehicles introduces the need for better understanding of the biological impacts of exposure to particulate matter emitted by the engines, a major urban health issue. The project will use the model of human lung cells (HEL, A549) to partly solve this problem. Respirable particles (PM2.5) from engine emissions produced by selected commonly used biofuels and, for comparison, by classic diesel fuel and gasoline, will be collected from various engines during various test cycles. The chemical analysis of extracts from sampled PM2.5 will be performed and selected toxicity markers will be analysed in cell cultures. Genome-wide transcriptomics and selected protein expression will be employed to get more insight into the mechanisms of biological efects of engine emissions. Combined use of chemical analysis with genomics will enable to identify major toxic emission components as well as biological pathways involved. The project will contribute substantially to direct comparison of mechanisms of the toxicity of biofuels with conventional fuels and may be used for a risk assessment.