3- Nitrofluoranthene

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-... 

Finally, while several volatile and semivolatile PAHs, e.g., naphthalene, the methylnaphthalenes, phenan-threne, pyrene, and fluoranthene, are not significant mutagens or carcinogens (hence not included in Table 10.13), they are precursors to powerful direct bacterial mutagens formed in gas-phase atmospheric reactions with hydroxyl during the day and nitrate radicals at night (see Section F). Furthermore, 2-nitrofluoranthene,... 

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. 

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). 

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. 

In the absence of cosolutes, the photodegradation rates depended on the orientation of the nitro group. Thus 1-nitropyrene decayed relatively fast by the nitro-nitrite primary intramolecular photorearrangement process, followed by secondary radical reactions. However, 2-nitropyrene and 2-nitrofluoranthene were stable toward photolysis, consistent with the N02 group being in the same plane as the aromatic rings. 

However, when H-atom-donating cosolutes, e.g., certain phenols, were added, the photodegradation rates of both 1-nitropyrene and 3-nitrofluoranthene increased. In this case, the reaction occurred via H-atom abstraction from the phenol by the electronically excited nitro-PAHs. Feilberg and Nielsen concluded that the photodegradation of nitro-PAHs on both diesel particles and wood smoke proceeds primarily by radical formation. However, H-atom abstraction by the excited triplet states of 1-nitropyrene and 2-nitrofluoranthene may also contribute. 

In the mid-1980s, the discovery of significant amounts of 2-nitropyrene in ambient particulate matter collected in a rural region of Denmark by Nielsen and co-workers (1984) and 2-nitrofluoranthene in southern California by Pitts and colleagues (1985b) provided unique initial evidence for the possible formation of nitroarenes by reactions of precursor PAHs in ambient air. Thus, these compounds are not electrophilic nitration products of their parent PAHs and are generally not observed in combustion sources such as diesel soot see, for example, Table 10.34 and the report of Ciccioli and co-workers on the detection of emissions of 2-nitrofluoranthene and 2-nitropyrene solely from a very minor Italian industrial source (see Ciccioli et al., 1993, 1995, 1996, and references therein). 

Subsequently, researchers confirmed the presence of 2-nitropyrene and 2-nitrofluoranthene in extracts of samples of ambient POM collected at sites throughout the world and reported 2-nitrofluoranthene levels that... 

For example, Legzdins and co-workers (1994) used the bioassay-directed fractionation and chemical analysis technique to isolate, identify, and quantify 2-nitrofluoranthene in extracts of ambient particles collected in Hamilton, Ontario, Canada. They found it accounted for 70% of the total nonpolar direct bacterial mutagenicity (strain YG1021, standard reversion assay, Maron and Ames, 1983). 

Additionally, in two different monitoring campaigns conducted in the center of Milan, Italy, Ciccioli and co-workers (1993) reported 2-nitrofluoranthene, 2-nitropyrene, and 1-nitropyrene were the only ni-troarenes detected. Subsequently, in a comprehensive study of the atmospheric formation and transport of 2-nitrofluoranthene and 2-nitropyrene, they established their presence and levels in ambient particles collected at sites located in urban, suburban, forest, and remote areas in Europe, Asia, America, and Antarctica (Ciccioli et al., 1996, and references therein see also Ciccioli et al., 1995). 

As an example of typical experimental data, Fig. 10.32 is a GC-MS selected ion monitoring (SIM) profile (m/z 247) for the nitrofluoranthenes and nitropy-renes in an extract of ambient particles collected in southern California (Arey et al., 1988b). The 1-nitropyrene (1-NP) and 3-nitrofluoranthene (3-NF) presumably are from diesel emissions (Tables 10.33 and 10.34), but the dominance of 2-nitrofluoranthene and 2-nitropyrene reflects a second major source. 

OH adduct radical (e.g., see Atkinson, 1994, and Chapter 6.G). However, in the presence of sufficient NOz, 2-nitrofluoranthene and 2-nitropyrene are formed and subsequently condense out on particle surfaces (see Pitts, 1987, Atkinson and Arey, 1994, Arey, 1998a, and references therein). 

Figure 10.35 is the GC-MS m/z 247 profile of the nitrofluoranthenes and nitropyrenes in an extract of an ambient particle sample collected at night (Arey et al., 1988b). The high ratio of 2-nitrofluoranthene to 2-nit-ropyrene observed in this nighttime sample is indicative of nighttime gas-phase NO, radical reactions (for a review, see Kwok et al., 1994b). An NO, radical initiated mechanism for atmospheric formation of 2-nitrofluoranthene is shown in Fig. 10.36 (Atkinson and Arey, 1997 Arey, 1998a, and references therein). Analogous to the OH reaction, NO, is proposed to add to the ring to form a fluoranthene-NO, adduct, followed by ortho addition of N02 and subsequent loss of HNO,. This reaction is noteworthy because of its selectivity i.e., only 2-nitrofluoranthene is formed, and in high yield (24%) compared to the OH-initiated daytime reaction (3%).

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). 

Ciccioli, P., A. Cecinato, E. Brancaleoni, M. Frattoni, and P. Zacchei, Formation and Transport of 2-Nitrofluoranthene and 2-Nitro-pyrene of Photochemical Origin in the Troposphere, J. Geophys. Res., 101, 19567-19581 (1996). 

Herreno-Saenz, D., F. E. Evans, T. Heinze, J. Lewtas, and P. P. Fu, "In Vitro Metabolism and DNA Adduct Formation from the Mutagenic Environmental Contaminant 2-Nitrofluoranthene, Chem. Res. Toxicol, 5, 863-869 (1992). 

Nielsen, T., and T. Ramdahl, Determination of 2-Nitrofluoranthene and 2-Nitropyrene in Ambient Particulate Matter Evidence for Atmospheric Reactions, Atmos. Environ., 20, 1507-1509 (1986). 

Sweetman, J. A., B. Zielinska, R. Atkinson, T. Ramdahl, A. M. Winer, and J. N. Pitts, Jr., A Possible Formation Pathway for the 2-Nitrofluoranthene Observed in Ambient Particulate Organic Matter, Atmos. Environ., 20, 235-238 (1986). 

In this study, the concentrations of several kinds of nitro-PAH, such as 1-nitropyrene (1-NP), 2-nitropyrene (2-NP), 2-nitrofluoranthene (2-NF), and 2-NTP, in the soluble organic fraction of airborne particles were determined by a column switching HPLC-chemiluminescence detection system in order to clarify the occurrence and behaviour of 2-NTP in the atmosphere. 

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