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 stud ied on fluoranthene and pyrene because of their large abundance. However, t he direct mutagenic activity of these nitro-PAHs can account for only up to about 20% of the total direct mutagenic activity of airborne particulate s amples, and the presence of unknown mutagenic nitro-PAHs was suggested. 1- and 2-Nitrotriphenylenes were first identified and quantified in ambient pa rticulate samples collected in Tokyo. Their mutagenicity and formation by l aboratory reactions of triphenylene deposited on a filter with NO2/ NO3/N2O 5 were also investigated. The concentrations of 1- and 2-nitrotriphenylenes were much higher than that of l-nitropyrene in the same samples. 2-Nitrotr iphenylene showed over 2 orders of magnitude greater mutagenic activity tha n 1-nitrotriphenylene in both strains TA98 and YG1024 (18 and 480 revertant s/nmol for 1-nitrotriphenylene and 3800 and 101 700 revertants/nmol for 2-n itrotriphenylene in TA98 and YG1024). The mutagenic 2-nitrotriphenylene was expected to contribute largely to the total mutagenic activity of the extr acts from airborne particulates. In addition, more effective formation of n itrotriphenylenes by the nighttime reaction of triphenylene in the presence of O-3 in the dark can explain the observation of high nitrotriphenylene c oncentration in the nighttime samples.