Quantification Of Ambient Nitrodibenzopyranones - Further Evidence For Atmospheric Mutagen Formation

2- and 4-nitro-6H-dibenzo[b,d]pyran-6-ones were quantified in ambient air samples collected in southern California and in the NIST SRM 1649 urban dust collected in Washington, DC. Lower concentrations of these nitrodibenzopyranones were observed in the NIST SRM 1650 diesel particulate material, and comparison of the concentrations of nitrodibenzopyranones, nitropyrenes, and nitrofluoranthenes in the SRMs 1649 and 1650 supports the conclusion that the nitrodibenzopyranones are formed in the atmosphere. 2-Nitrodibenzopyranone was determined to be a significant contributor of ambient air particle- and gas-phase mutagenicity, as assayed with the microsuspension modification of the standard Ames Salmonella plate incorporation test using strain TA98, without activation. Formation yields of the 2- and 4-nitrodibenzopyranones observed in environmental chamber experiments of the OH radical-initiated reaction of phenanthrene are compared to those derived from ambient air observations.