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This work assessed the impact of fuelling an automotive engine with palm biodiesel(pure,and two blends of 10％and 20％with diesel,B100,B1O and B20,respectively)operating un-der representative urban driving conditions on 17 priority polycyclic aromatic hydrocarbon(PAH)compounds,oxidative potential of ascorbic acid(OPAA),and ecotoxicity through Daph-nia pulex mortality test.PM diluted with filtered fresh air(WD)gathered in a minitunel,and particulate matter(PM)collected directly from the exhaust gas stream(W/oD)were used for comparison.Results showed that PM collecting method significantly impact PAH con-centration.Although all PAH appeared in both,WD and W/oD,higher concentrations were obtained in the last case.Increasing biodiesel concentration in the fuel blend decreased all PAH compounds,and those with 3 and 5 aromatic rings were the most abundant.Palm biodiesel affected both OPAA and ecotoxicity.While B10 and B20 exhibited the same rate of ascorbic acid(AA)depletion,B100 showed significant faster oxidation rate during the first four minutes and oxidized 10％more AA at the end of the test.B100 and B20were signifi-cantly more ecotoxic than B10.The lethal concentration LC50 for B10 was 6.13 mg/L.It was concluded that palm biodiesel decreased PAH compounds,but increased the oxidative po-tential and ecotoxicity.