Health Assessment Document for Diesel Emissions - NSCEP | US ...

1 sample collection. There was no breakdown of traffic into numbers of diesel- and gasoline-
2 fueled vehicles.
3 The range of particle-phase P AH concentrations and the mean particle- and vapor-phase
4 PAH concentrations for 48 samples collected in the tunnel are tabulated in Table 2-16. The
5 ratios of mean particle-phase PAH concentrations to that ofB[e]P, which is considered to be a
6 nonreactive PAH, are also given in this table.
7 As can be seen from Table 2-l6, alkyl-substituted phenanthrenes in the tunnel samples
8 had relatively high concentrations compared with those of the parent compound. This suggests a
9 significant contribution from diesel vehicle emissions (particularly diesel-fueled trucks) because
1 0 extracts of diesel particulate matter are known to have significant concentrations of methyl and
11 dimethylphenanthrenes (see Table 2-8 and Yu and Hites, 1981).
12 Factor analysis was applied to the tunnel data in an attemptto identify factors associated
13 with different types of vehicles; two factors were obtained. The alkylated phenanthrenes loaded
14 significantly on factor 1, suggesting the diesel vehicles as the source of these compounds.
15 Several of the higher-molecular-weight P AHs loaded onto factor 2, which may be associated
16 with the contribution of gasoline-fueled emissions in the tunnel.
17 Ambient air sampling for P AHs was also conducted during a summertime photochemical
18 air pollution episode in Glendora, CA, at· a site situated less than 1 km froin the heavily traveled
19 I-210 freeway and generally downwind ofLos Angeles; therefore, the site was affected by motor
20 vehicle emissions (Atkinson et al., 1988). Samples were collected by means ofhigh-volume
21 samplers equipped with Teflon-impregnated glass-fiber filters backed by PUF plugs. Table 2-17
22 shows the average (from three daytime and three nighttime samples) concentrations of P AH
23 measured and the ratios of these concentrations to that ofB[e ]P. Unfortunately, no alkylated
24 phenanthrenes were measured.
25 As can be seen from the comparison of Tables 2-16 and 2-17, the concentrations of all
26 P AHs measured in Glendora were much lower than those measured in the tunnel, as would be
27 expected. However, the ratios of the concentrations of particle-bound PAH to those ofB[e]P
28 were also different for the two sites, usually much lower for the Glendora site (except for higher
29 molecular weight PAHs, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, and coronene). This may
30 indicate either contributions from sources other than motor vehicles in the Glendora study or
31 P AH photochemical transformations occurring on particles prior to or during high-volume
32 sample collections (or both). The generally higher P AH concentrations for nighttime versus
33 daytime sampling periods (Atkinson et al., 1988) seem to support the latter possibility. However,
34 the influence of meteorology cannot be excluded. This conclusion is also consistent with high
35 levels of photochemical pollutants observed in Glendora; for example, the daily maxima of 0 3
2/1/98 2-49 DRAFT --DO NOT CITE OR QUOTE