Ultralow sulfur diesel (ULSD) fuel was blended with 5%, 10%, 15% and 20% of butanol by volume. The effects of these blended fuels on physicochemical characteristics of particulate emissions and the cytotoxicity of particulate extracts from a single cylinder, direct injection stationary diesel engine were investigated with the engine working at a constant speed of 3000 revolutions per min (rpm) and at 25%, 50% and 75% of its maximum output power. The results indicated a decrease in particulate mass and elemental carbon (EC) emissions, while an increase in the proportion of organic carbon (OC) in the particles with an increase in butanol in the fuel. Compared to the ULSD, the total number concentrations of volatile and non-volatile particles were reduced significantly for blended fuels, whereas the number of particles with diameter less than 15 nm increased for 15% and 20% butanol blends at low engine load. The increased total polycyclic aromatic hydrocarbons (PAHs) emissions, as well as their carcinogenic potency was also observed when the blends contained 15% and 20% butanol. In general, all the particle extracts showed a decline in cell viability with their increased dose and with the increased engine load while maintaining the same dose, based on the MTT assay. (C) 2013 Elsevier Ltd. All rights reserved.