Biological toxicities of emissions from an unmodified engine fueled with diesel and biodiesel blend.

Conventional diesel and palm oil methyl esters were blended in 6 ratios (0, 10, 30, 50, 75 and 100% of biodiesel by volume) and fed into an unmodified 4-stroke engine with a constant output power. The semi-volatile and particulate products in the exhaust were collected separately and their biological toxicities evaluated by both Microtox test and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The Microtox test indicates that the TUVs (toxicity unit per liter exhaust sampled, TU/L-exhaust) in the semi-volatile extracts were 3 to 5 times those of the particulate extracts. Diesel particulates had the highest unit toxicity, TUW (toxicity unit per microg soluble organic fraction of particulate, TU/microg particle SOF) of all of the other biodiesel blends. According to the Microtox tests results, the effect of biodiesel blending in MTT assay demonstrated higher toxicity in the semi-volatile products than the particulates.