Recently, we developed a highly sensitive analyzer for the determination of nitroarenes in environmental samples, and determined the levels of strongly mutagenic nitroarenes such as 1,3-dinitropyrene (1,3-DNP), 1,6-DNP, 1,8-DNP and 1-nitropyrene (1-NP) in benzene/ethanol extracts from airborne particulates. We also reported that automobiles were the major source in downtown areas and the contribution of diesel-engined vehicles were much larger than that of gasoline-engined vehicles. With regard to the increase in lung cancer in recent years, we examined the distributions of 1,3-DNP, 1,6-DNA, 1,8-DNP, 1-NP and mutagenicity in relation to airborne particulate size using an Andersen high-volume air sampler and estimated the contributions of these compounds to atmospheric mutagenicity for the present report. Mutagenicities of extracts from fractionated particulates were determined by the Ames test usingS. typhimurium strains without S9 mix, while concentrations of DNPs and 1-NP in the same extracts were determined by nitroarene analyzer.In the particulate fraction smaller than 1.1 μm, mutagenic activities of 68% and 75% of the total were observed in TA98 and YG1024 strains, respectively. In the same fraction, 65-82% of the total DNPs as well as 84% of the total 1-NP were observed. Supposing that there was not any coexisting compound affecting the mutagenicities of these compounds in this fraction, their calculated mutagenic contributions were respectively 0.6% (1,3-DNP), 1.2% (1,6-DNP), 1.8% (1,8-DNP) and 1.6% (1-NP) in the TA98 strain, and 2.5% (1,3-DNP), 5% (1,6-DNP), 9% (1,8-DNP) and 2.1% (1-NP) in the YG1024 strain. Thus, large mutagenic contributions of not only airborne particulates smaller than 1.1 μm but also DNPs and 1-NP in this fraction suggested that the atmospheric behavior of these compounds should be clarified, as they are potent air pollutants.