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 ...