Ambient Measurement of Nitrotriphenylenes and Possibility of Nitrotriphenylene Formation by Atmospheric Reaction

Environmental nitration of PAHs by nitrogen oxides on airborne particulates and identification and quantification of nitro-PAHs in them have been studied on fluoranthene and pyrene because of their large abundance. However, the direct mutagenic activity of these nitro-PAHs can account for only up to about 20% of the total direct mutagenic activity of airborne particulate samples, and the presence of unknown mutagenic nitro-PAHs was suggested. 1- and 2-Nitrotriphenylenes were first identified and quantified in ambient particulate samples collected in Tokyo. Their mutagenicity and formation by laboratory reactions of triphenylene deposited on a filter with NO 2 / NO 3 /N 2 O 5 were also investigated. The concentrations of 1- and 2-nitrotriphenylenes were much higher than that of 1-nitropyrene in the same samples. 2-Nitrotriphenylene showed over 2 orders of magnitude greater mutagenic activity than 1-nitrotriphenylene in both strains TA98 and YG1024 (18 and 480 revertants/nmol for 1-nitrotriphenylene and 3800 and 101 700 revertants/nmol for 2-nitrotriphenylene in TA98 and YG1024). The mutagenic 2-nitrotriphenylene was expected to contribute largely to the total mutagenic activity of the extracts from airborne particulates. In addition, more effective formation of nitrotriphenylenes by the nighttime reaction of triphenylene in the presence of O 3 in the dark can explain the observation of high nitrotriphenylene concentration in the nighttime samples.