Co

74 '75 '76 '11 '78 '79 '80 '81 '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92

Year and season

FIGURE 10.20 Seasonal concentrations of benzo[a]pyrene (ng m~3) and direct (-S9 mix) and indirect ( + S9 mix) mutagenicities (rev m~3) on TA98, Ames Salmonella typhimurium assay with the "preincubation procedure" of Yahagi et al. (1977) of ambient aerosols collected annually during the winter, spring, summer, and autumn for 18 years (1974-1992) in Sapporo, Japan (adapted from Matsumoto et al., 1998).

74 '75 '76 '11 '78 '79 '80 '81 '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92

Year and season

FIGURE 10.20 Seasonal concentrations of benzo[a]pyrene (ng m~3) and direct (-S9 mix) and indirect ( + S9 mix) mutagenicities (rev m~3) on TA98, Ames Salmonella typhimurium assay with the "preincubation procedure" of Yahagi et al. (1977) of ambient aerosols collected annually during the winter, spring, summer, and autumn for 18 years (1974-1992) in Sapporo, Japan (adapted from Matsumoto et al., 1998).

Matsumoto and co-workers rationalize their results for BaP levels and the increasing ratio of direct/indirect in terms of changes in source strengths. Thus, there was a large decrease in coal consumption in the Sapporo area, from ~ 375,000 tons in 1975 to only ~20 tons in 1992. Concurrently, there was a large increase in the number of motor vehicles in that area, from ~ 300,000 in 1975 to over one million in 1992, and the percentage of diesel-powered vehicles went from <10% in 1975 to 32% in 1992.

Additionally, starting in the mid-1970s, there were stricter regulations on the sulfur content of fuel oil. These, coupled with the large decrease in coal use, are reflected in ambient S02 levels, which, for example, in the wintertime dropped from ~30 ppb in 1975-1976 to ~7 ppb in 1991-1992.

They concluded that, given the fact that over f8 years the direct mutagenicity of ambient particles remained unchanged while the concentration of BaP dropped significantly, BaP is not a good indicator of the mutagenicity/carcinogenicity of extracts of ambient particles. Finally, in agreement with other studies (see Sections E and F), they suggested more attention be paid to nitro-PACs "emitted directly from diesel-powered vehicles" as well as those formed secondarily in atmospheric reactions involving NOx.

A number of studies of bacterial mutagenicity and the PAHs and PACs responsible for it have been carried out in southern California. At the risk of seeming somewhat parochial, we describe briefly the results of some of them, since they are unique in the breadth of parameters and species measured concurrently. A key objective of these studies was to better understand the role played by atmospheric reactions in determining the composition and mutagenicity of fine particles in polluted air parcels at or near their point of origin (e.g., Long Beach and downtown Los Angeles) and subsequently during transport to cities ~40-110 km downwind. While specific results from this area are presented, the major conclusions should be generally applicable to major polluted airsheds throughout the world, e.g., Mexico City (Villalobos-Pietrini et al., 1995).

For example, Atkinson and co-workers (1988a) sampled at seven sites across California in 1986-1987, selected because they had different emission sources (see Table 10.22). The eighth site, San Nicholas Island (~ 130 km offshore in the Pacific Ocean, Fig. 10.21), was chosen as the "upwind" regional background site. A total of 118 sets of 12-h duration daytime and nighttime gas- and particle-phase samples were obtained and 35 PAHs, 9 nitroarenes, and dibenzothio-phene were identified and quantified. Particle-phase mutagenicities of samples were assayed on strains TA98 + S9 and -S9 as well as strains TA98NR and TA98/l,8-DNPh, all without activation (-S9).

As seen in Fig. 10.22, at the six mainland sites, there was a correlation between direct-acting POM mutagen densities (rev m~3) and measured concentrations (pg m~3) of the strong, direct mutagen 2-nitropyrene (16,000 rev /¿g~'). This nitroarene is not present in primary combustion emissions (possible exceptions are rare); rather, it is formed in both ambient and simulated polluted atmospheres as a product of the homogeneous gas-phase reaction of OH radicals with pyrene (see Section F, articles by Nielsen et al. (1984), Pitts et al. (1985b), Nielsen and Ramdahl (1986), Sweetman et al. (1986), Winer and Atkinson (1987), and Zielinska et al. (1989a), and reviews by Pitts (1987), Zielinska et al. (1990), Atkinson and Arey (1994) and Arey (1998a)). Furthermore, changes in the ambient PAH burden that

TABLE 10.22 Average ( + S9 and -S9) and Highest (-S9) Values of Mutagenicityb (rev m ') of Ambient Particles Collected' at Seven Cities / Sites in California'1 with Different Types of Emission Sources"

Average mutagenicity

Sampling Source (rev m • ), TA98 Highest value dates Location characterization + S9 — S9 (-S9)

8/86 Glendora Motorvehicle 33 35 61

10/86 Yuba City Agricultural burning 24 30 95

12/86-1/87 Concord Industrial 63 62 130

2-3/87 Mammoth Lakes Woodburning 22 7 17 (84 with S9)

3-4/87 Oildale Oil production 10 9 20 5-6/87 Reseda Residential 19 22 50 7/87 Pt. Arguello Rural 0.2 0.4 0.5

" Adapted from Atkinson et al. (1988a).

6 Mutagen density (rev m~3) on strain TA98, standard Ames plate incorporation Salmonella typhimurium reversion array. ' 12-h daytime or nighttime duration; Hi-Vol sampler with 10-jum cutoff. '' See Fig. 10.21.

Yuba City 30/24*

San] Francisco

Pacific Ocean

Point I Arguello 0.4/0.2*

Mammoth Lakes 7/22*

Reseda 22/19*

Glendora j 35/33* J^Los Angeles

San Nicolas = Island

FIGURE 10.21 Twenty-four-hour average values of mutagenicity levels of ambient particulate matter [rev m~3, TA98 with (*) and without S9] collected at seven sites in California significantly impacted by different types of combustion-generated emission sources: Glendora (motor vehicle), Yuba City (agricultural burning), Concord (industrial), Mammoth Lakes (major wintertime ski area, ~ 2500-m elevation, wood-burning and motor vehicle emissions), Oildale (oil production), Reseda (residential), and Point Arguello (rural); also shown is San Nicholas Island (upwind regional background). Standard Ames plate incorporation Salmonella typhimurium reversion assay; 12-h sampling periods, day and night: 8/86, 10/86, 12/86-1/87, 2-3/87, 3-4/87, 5-6/87, and 7/87; San Francisco and Los Angeles are included for reference to the locations of the actual sampling sites (adapted from Atkinson et al., 1988a).

took place during transport of a given air parcel from its initial source to the sampler at each downwind site were "mirrored" by the measured direct-acting mutagenicities of the transported aerosols, suggesting that the direct mutagenicity is due to the atmospheric reaction products of the primary PAH emissions. Finally, based on the measured concentrations of directly mutagenic MW 247 nitroarenes (2-nitrofluoranthene, 8-nitrofluoranthene, 1-nitropyrene, and 2-nitropyrene) in the POM samples collected at the different locations and the specific activities of the compounds, these nitro-PAHs were estimated to contribute no more than ~f0% (and generally <5%) to the total ambient direct mutagen densities at those sites; the remaining ~90% of the direct mutagenicity is at least partially due to more polar compounds formed in atmospheric reactions (Atkinson et al., 1988a).

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