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This study investigates the size distribution of nano/ultrafine particle-bound PAHs (polycyclic aromatic hydrocarbons) and the PAH-associated carcinogenic potency/cytotoxicity of the exhaust from a generator that is fuelled with D100 (pure petroleum diesel) and S20 (v/v = 20% soy-biodiesel/80% D100) and operated at stable energy output loads (0 and 3 kW). A micro-orifice uniform deposit impactor (MOUDI) and a Nano-MOUDI (with aerodynamic diameters of 0.01-18 μm) were used to collect PM samples. The cytotoxicity of the organic solvent extracts of PM samples to the human male monocytic cell strain (U937) was evaluated using the MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The results indicate that at both loads, using S20 in place of D100 effectively reduced the emissions of DEPs, PAHs in the DEPs, and PAHs-associated BaP eq ; furthermore, the unit mass cytotoxicity of ultrafine particles and nano-particles in the DEPs was also lowered (by an average of 52.6%). Therefore, soybean biodiesel (S20) can be used as an alternative fuel to petroleum diesel to reduce the hazards of emissions from diesel engines to human health.

This study used pure fossil diesel (D100) and a 20% (v/v, volume percent) waste-edible-oil-biodiesel blend (W20, 20% waste-edible-oil-biodiesel + 80% diesel) as the fuels for a generator to investigate the mass concentrations of various sized PMs (PM 0.01-0.056 (nano particles), PM 0.01-0.1 (ultrafine particles), PM 0.01-1 (submicron particles), PM 0.01-2.5 (fine particles), PM 0.01-10 and PM 0.01-18 ) and particle-bound carbons, polycyclic aromatic hydrocarbons (PAHs), and PAHs' toxicity equivalences (BaP eq ) in generator emissions. The engine load was set as either 0 or 3 kW. MOUDIs and Nano-MOUDIs were used as the samplers. Human male single cells (U937) and the method MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) were used to test the cell toxicity of particle extracts (obtained from organic-solvent extraction). The results showed that, compared with D100, using W20 effectively reduced the PM (by 21.0-72.8%), particulate EC (by 2.69-57.3%), particulate OC (by 30.8-47.5%), Total-PAHs (by 64.1-81.9%), and Total-BaP eq (by 70.9-92.6%) in all sized particles emitted from the diesel generator, regardless of engine load. The reduction of PM 0.01-18 (81.3%) was higher in the lung respirable accumulation mode particles (PM 0.1-1 ). Regardless of fuel and loading, the emitted PM 0.01-18 exhibited a single-modal distribution and peaked in the submicron size range (0.18-0.32 μm). Compared with no engine load, with the exception of PM 0.01-0.1 and PM 0.01-0.056 , the OC contents of various particle sizes in PM at 3 kW engine load using D100 and W20 were all reduced (by 13.3-15.0% and 28.9-31.7%, respectively), while the EC content increased (by 27.5-29.1% and 37.9-41.4%, respectively). Moreover, the cell toxicity to U937 (per μg PM) of particle extract was higher for nano ) and ultrafine (PM 0.056-0.1 ) particles than for the other sized ones. However, compared with D100, using W20 could reduce the cell toxicity to U937 (per μg PM) of extracts from all sized particles, especially for nano and ultrafine particles (reduction = 32-46%) at 3 kW engine load.

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