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

1 with four to seven rings), which accounted for only 0.8% of the total weight ofDPM condensate,
2 .produced the highest incidence of lung carcinomas following implantation into the rat lungs. A
3 carcinoma incidence of 17.1% was observed following implantation of 0.21 mg lib/rat, whereas
4 the nitro-PAH fraction (lid) at 0.18 mg/rat accounted for only a 2.8% carcinoma incidence.
· 5 Hydrophilic fractions ofthe DPM extracts, vehicle (beeswax/trioctanoin) controls, and untreated
6 controls failed to exhibit carcinoma formation. Administration of all hydrophobic fractions (lia-
7 d) produced a carcinoma incidence (20%) similar to the summed incidence of fraction lib
8 (17.1 %) and lid (2.8%). The B[a]P positive controls (0.03, 0.1, 0.3 mg/rat) yielded a carcinoma
9 incidence of 8.6%, 31.4%, and 77.1 %, respectively. The study showed that the tumorigenic
10 agents were primarily four- to seven-ring P AHs and, to a lesser extent, nitroaromatics. However,
11 these studies demonstrated that simultaneous administration of various P AH compounds resulted
12 in a varying of the tumorigenic effect, thereby implying that the tumorigenic potency of P AH
13 mixtures may not depend on ariy one individual P AH. This study did not provide any
14 information regarding the bioavailability of the particle-associated P AHs that might be
15 responsible for carcinogenicitY.
16 Kawabata et al. ( 1986) compared the effects of activated carbon and diesel exhaust on
17 lung tumor formation. One group of 59 F344 rats was intratracheally instilled with DPM 1
18 mg/week for 10 weeks). A second group of 31 rats was instilled with the same dosing regime of
19 activated carbon. Twenty-seven rats received oniy the. solvent (buffered saline with 0.05%
20 Tween 80), and 53 rats were uninjected. Rats dying after 18 mo were autopsied. All animals
21 .surviving 30 moor more postinstillation were sacrificed and evaluated for histopathology.
22 Among 42 animals exposed to DPM surviving 18 mo or more, tumors were reported in 31,
23 including 20 malignancies. In the subgroup surviving for 30 mo, tumors were detected in 19 of
24 20 animals, including 1 0 malignancies. Among the rats exposed to activated carbon, the
25 incidence of lung tumors equaled 11 of23 autopsied, with 7 cases of malignancy. Data for those
26 ·dying between 18 and 30 mo and those sacrificed at 30 mo were not reported separately.
27 Statistical analysis indicated that activated carbon induced a significant increase in lung tumor
28 incidence compared with no tumors in 50 uninjected controls and 1 tumor in 23 solvent-injected
29 controls. The tumor incidence increase was significant inthe DPM-instilled group and was
30 significantly greater than the increase in the carbon-instilled group. This study provides evidence
31 for the carcinogenicity of DPM. It also shows, as Heinrich et al. (1995) and Nikula et al. (1995)
32 did, that particles lacking organic constituents also can induce tumors.
33 Dasenbrock et al. (1996) conducted a study to determine the relative importance of the
34 organi'c constituents of diesel particles and particle surface area in the induction of lung cancer in
35 rats. Fifty-two female Wistar rats were intratracheally instilled with 16-17 doses of diesel
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