The contribution of nitro- and methylnitro-naphthalenes to the vapor-phase mutagenicity of ambient air samples

1- and 2-Nitronaphthalene (NN) and the 14 methylnitronaphthalene (MNN) isomers were identified and quantified in ambient vapor-phase samples collected in Redlands, CA during moderate photochemical air pollution. The mutagenic activities of NN and MNN standards were determined using a microsuspension-preincubation modification of the Ames Salmonella bacterial reversion assay in strain TA98 without microsomal activation. The calculated contributions of the NNs and MNNs to the total vapor-phase ambient mutagenic activity were similar to 18 and similar to 32% for daytime and nighttime composite samples, respectively. Enhanced mutagenic activity in the nighttime sample was attributed to NN and MNN formation from nighttime NO3 radical-initiated reactions of naphthalene and the methylnaphthalenes. Copyright (C) 1996 Elsevier Science Ltd