Mutagenicity of ambient air

With the carcinogenic and mutagenic properties of certain key airborne PAHs and PACs as background, let us now examine the contributions of these genotoxic compounds to the bacterial and human cell mutagenicities of ambient air. 

Finally, in the context of the overall vapor-phase mutagenicity of ambient air, we note that significant fractions of the two powerful human cell and bacterial mutagens discussed earlier, cyclopen ta[c<7]pyrene (XXVIII) and 2-nitrodibenzopyranone (XI), have been found in the gas phase (i.e., trapped on PUF plugs) in samples collected during hot weather at sites in southern California (Fraser et al., 1998, and Arey et al., 1994, respectively). Flence the contributions of such species, which are normally considered to be primarily in the particle phase, to the gas-phase mutagenicity at high ambient temperatures should also be considered. 

As discussed earlier (see Fig. 10.26), the contributions of 1- and 2-nitronaphthalenes and the methylni-tronaphthalene isomers to the vapor-phase mutagenicity of extracts of daytime and nighttime samples of ambient air in Redlands, California, were determined by Gupta and co-workers (1996) and shown to be major contributors to the overall vapor-phase mutagenicity of ambient air. Furthermore, the researchers demonstrated that both daytime OH radical initiated and nighttime N03 radical initiated reactions of naphthalene and the methylnaphthalenes are important in pol-... 

Gupta, P., W. P. Harger, and J. Arey, The Contribution of Nitro-and Methylnitronaphthalenes to the Vapor-Phase Mutagenicity of Ambient Air Samples, Atmos. Environ., 30, 3157-3166 (1996). 

KolberA, WolffT, HughesT, etal. 1981. Collection, chemicalfractionation, and mutagenicity bioassay of ambient air particulate. In Short term bioassays in the analysis of complex environ mix II, 21-44. 

The mutagenic potency of a POM extract is generally expressed in units of revertants per microgram (rev /rg l) of the dried organic extract of the sample (sometimes, however, as rev mg-1 of the original particulate matter). The concentration of mutagens in ambient air (or synthetic laboratory atmospheres)... 

A number of variables influence the overall levels of mutagenicity to which the general public is exposed through inhalation of ambient air particles. (Note, however, that total exposure also includes gas-phase mutagens see later.) The factors include, for example, (a) the inherent mutagenic potencies (rev /Ag" of extract) of the fine particles emitted by each type of combustion... 

The impact of close proximity to a major source on the mutagenicity levels of ambient air particles (rev m 3) is seen in Fig. 10.17 for a site immediately adjacent to, and generally downwind from, a heavily traveled freeway in west Los Angeles (Pitts et al., 1985a). Peak levels were 120 ( + S9) and 100 ( —S9) rev m-3 during the midmorning rush hour and — 110 ( + S9)... 

De Raat, W. K., F. L. Schulting, E. Burghardt, and F. A. de Meijere, Application of Polyurethane Foam for Sampling Volatile Mutagens from Ambient Air, Sci. Total Environ., 63, 175-189 (1987). 

Watts, R. R., R. J. Drago, R. G. Merrill, R. W. Williams, E. Perry, and J. Lewtas, Wood Smoke Impacted Air Mutagenicity and Chemical Analysis of Ambient Air in a Residential Area of Juneau, Alaska, JAPCA, 38, 652-660 (1988). 

Wise, S. A., S. N. Chesler, L. R. Hilpert, W. E. May, R. E. Rebbert, C. R. Vogt, M. G. Nishioka, A. Austin, and J. Lewtas, Quantification of Polycyclic Aromatic Hydrocarbons and Nitro-Sub-stituted Polycyclic Aromatic Hydrocarbons and Mutagenicity Testing for the Characterization of Ambient Air Particulate Matter, Environ. Int., II, 147-160 (1985). 

Claxton LD, Woodall GM (2007) A review of the mutagenicity and rodent carcinogenicity of ambient air. Mutat Res Rev Mutat Res 636 36-94 Claxton LD, Matthews PP, Warren SH (2004) The genotoxicity of ambient outdoor air, a review Salmonella mutagenicity. Mutat Res Rev Mutat Res 567 347-399 Clemons JH, Allan LM, Marvin CH, Wu Z, McCarry BE, Bryant DW, Zacharewski TR (1998) Evidence of estrogen- and TCDD-like activities in crude and fractionated extracts of PMIO air particulate material using in vitro gene expression assays. Environ Sci Technol 32 1853-1860... 

Singh HB, Salas LJ, Stiles RE. 1982. Distribution of selected gaseous organic mutagens and suspect carcinogens in ambient air. Environmental Science and Technology 16 872-880. 

Helmig D, J Arey, WP Harger, R Atkinson, J Lopez-Cancio (1992a) Formation of mutagenic nitrodibenzopy-ranones and their occurrence in ambient air. Environ Sci Technol 26 622-624. 

TABLE 10.13 Carcinogenicities of Selected PAHs in Ambient Air As Evaluated by IARC, U.S. EPA, and U.S. DHHS, Cancer Potency Equivalence Factors Relative to BaP = 1.00 from Nielsen et al. (1996), CARB (1994), and Collins et al. (1998), and Human Cell Mutagenicities Relative to BaP = 1.00... 

Box 10.9), a new class of mutagenic compounds was discovered, the nitroarenes. Within a short time, they were identified as directly mutagenic copollutants present along with well-known promutagenic PAHs in combustion-generated emissions and distributed worldwide in urban ambient air (see Section D). 

YG1024 is 30 times more sensitive than TA98 to 1,8-dinitropyrene (2,150,000 vs 72,200 rev/nmol -S9). For example, Legzdins and co-workers (1994) used the enhanced response of strain YG1021 to determine the mutagenicities of 14 PAHs, and several nitroarenes, S-atom PACs, and O-atom PACs in the ambient air of Hamilton, Ontario, Canada. 

This modification has been applied in a variety of studies, including the mutagenic activity of fine ambient air particles as a function of particle size (Kado et... 

Until the early to mid-1980s, research on the mutagenicity of respirable POM focused almost exclusively on the particulate phase. Another aspect of tropospheric chemistry with significant health implications is the application of the Ames bacterial assay (with or without the microsuspension modification) to the detection and identification of mutagenic vapor-phase PAHs and PACs. For example, Harger and co-workers (1992) reported that the mutagenicities of concurrently collected samples of vapor-phase and particle-phase organics in southern California (Claremont, California) ambient air were comparable. 

Recently, Enya and co-workers (1997) identified another very powerful type of direct mutagen, the nitro-PAH ketone 3-nitrobenzanthrone (3-nitro-7/f-benz[<7e]anthracen-7-one, XXIV), in extracts of particles from ambient air and diesel exhaust ... 

Members of another class of powerful direct mutagens, four nitroazabenzo[a]pyrene derivatives, were identified by Sera and co-workers (1994) in the basic fraction of extracts of diesel exhaust and in ambient POM. Structures and direct mutagenic activities on strains TA98 and YG1024 (-S9 mix) of the 1- and 3-nitro-6-azabenzo[a]pyrenes and the 1- and 3-nitro-6-azabenzo[a]pyrene-7V-oxides are shown in Table 10.21 (Sera et al., 1992 Fukuhara et al., 1992). They have been measured in ambient air in Fukuoka, Japan, at concentrations of 1.1, 1.2, 0.8, and 0.3 ng/g, respec-... 

Dibenzo[a,/]pyrene, a potent mutagen in the MCL-5 assay, was not detected in this analysis of SRM 1649. However, this 6-ring PAH XXIX was identified (but not quantified) by comparison to an authentic standard by Allen and co-workers (1998) in their analysis of size-segregated aerosols in urban Boston ambient air. Furthermore, in their August 1994 study of biologically active, particle-associated PAHs in ambient Riverside, California, Atkinson and Arey (1997) measured concentrations of 18, 20, and 15 pg m-3 of this compound for one daytime and two nighttime sampling events, respectively. These concentrations were 40-50% of the BaP concentrations in the same aerosol samples. 

In a laboratory environmental chamber study of the gas-phase photooxidation of naphthalene and phenan-threne, Sasaki and co-workers (1997b) found two products, 2-nitronaphthalene and 2-nitrodibenzopyranone (XI), that displayed significant genotoxicity in the MCL-5 human cell assay. This finding emphasized the importance of atmospheric reactions in forming mutagens, since the concentrations of such compounds are relatively high in ambient air compared to those expected for nitroarenes directly emitted from primary combustion sources (see Section F). 

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