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 (PM0.01–0.056 (nano particles), PM0.01–0.1 (ultrafine particles), PM0.01–1 (submicron particles), PM0.01–2.5 (fine particles), PM0.01–10 and PM0.01–18) and particle-bound carbons, polycyclic aromatic hydrocarbons (PAHs), and PAHs’ toxicity equivalences (BaPeq) 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-BaPeq (by 70.9–92.6%) in all sized particles emitted from the diesel generator, regardless of engine load. The reduction of PM0.01–18 (81.3%) was higher in the lung respirable accumulation mode particles (PM0.1–1). Regardless of fuel and loading, the emitted PM0.01–18 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 PM0.01–0.1 and PM0.01–0.056, 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 (PM0.01–0.056) and ultrafine (PM0.056–0.1) 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.