Nitrofluoranthenes, atmospheric production

BaP, benzo[g/z/]perylene, benzo[6]fluoranthene, in-deno[l,2,3-cd]pyrene, and benzo[/c]fluoranthene, contribute the major portion of the identifiable mutagenicity of the extract of the whole unfractionated sample, accounting for 8.6, 2.5, 1.7, 1.4, 1.2, and 0.8%, respectively, of the total mutagenicity of the whole sample. Two semipolar mutagenic PACs were also present at significant levels 2-nitrofluoranthene, a product of atmospheric reactions, and 6//-benzo[c<7]pyren-6-one, a primary O-PAC pollutant present in exhaust emissions from diesel engines and non-catalyst-equipped cars (see Sections E and F). These account for an additional 0.8 and 1.6%, respectively, of the identified whole sample mutagenic potency (see Table 10.26). 

Chemical/Physical. 2-Nitrofluoranthene was the principal product formed from the gas-phase reaction of fluoranthene with OH radicals in a NOx atmosphere. Minor products found include 7-... 

In 1997, Busby and co-workers reported that 2-nitrofluoranthene, an important product of atmospheric transformations (vide infra) was inactive in MCL-5 cells but a potent mutagen in hlAlv2 cells another important atmospheric reaction product, the nitrophenanthrene lactone 2-nitrodibenzopyranone (XI), was inactive in both hlAlv2 and MCL-5 cells. Furthermore, it was nonmutagenic in the forward mutation bacterial assay in the absence of rat liver postmi-tochondrial supernatant (-S9) but was mutagenic with the addition of S9 mix. 

The toxicology-based conclusion that the minimum concentration for 2-nitrofluoranthene to be an important human cell mutagen is 1 p.g/g, coupled with air quality sampling data showing its concentrations in respirable particles sampled from ambient air can in fact reach 10 pg/g, provides a useful example of a productive symbiotic interaction between atmospheric chemists and toxicologists. Such interactions are essential for reliable risk assessments of air pollution and human health effects of complex combustion-generated mixtures of gases and particles. 

As we have seen, key nitroarenes found in extracts of ambient particulate matter are 1-nitropyrene (1-N02-Py), predominant in primary combustion emissions, and 2-nitrofluoranthene and 2-nitropyrene, major products of gas-phase atmospheric reactions. Here we focus simply on their atmospheric fates as particle-bound species participating in heterogeneous decay processes. Formation of such nitro-PAHs in gas-phase reactions is addressed in Section F. 

Busby, W. F., Jr., H. Smith, C. L. Crespi, B. W. Penman, and A. L. Lafleur, Mutagenicity of the Atmospheric Transformation Products 2-Nitrofluoranthene and 2-Nitrodibenzopyranone in Salmonella and Human Cell Forward Mutation Assays, Mutat. Res., 389, 261-270 (1997). 

In ambient air samples analyzed by GC-MS, different peaks of isomers of nitropyrenes and nitrofluoranthenes can be observed (Fig. 2). Some of these products are combustion-derived, while others primarily originate from atmospheric reactions. Some previously reported extremely high concentrations of 1-NP [31] might be partly explained by poor separation and identification of different isomers of 1-NP in high-performance liquid chromatography (HPLC) analysis equipped with fluorescence detection. 

Figure 2 Chromatograms of GC MS-MS analyses of emissions from a diesel engine (upper panel) and from an ambient air samples (lower panel) under similar conditions. The product ion m/z 216 corresponds to HFB-derivatized 1-AP, whereas the product ion m/z 225 corresponds to the derivatized deuterated internal standard D9-I -AP (upper panel). The lower panel shows nine different products of which one was identified as 1-NP (4), presumably deriving from combustion sources. Four other peaks were tentatively identified (by cochromatography with a reference standard) as 3-nitrofluoranthene (1), 4-nitro-pyrene (2), 2-nitrofluoranthene (3), and 2-nitropyene (5), presumably primarily from atmospheric origin. The four remaining peaks (in the product ion trace m/z 244) did not coelute with available reference compounds.

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