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

1 the differences were the result of a learning deficit or due to some other cause (e.g., motivational
2 , or arousal differences).
3 These data are difficult to interpret in terms of health hazards to humans under ambient
4- environmental conditions because of the high concentration of diesel exhaust to which the
5 laboratory rats were exposed. Additionally, there are no further concentration-response studies to
6 assess at what exposure levels these observed results persist or abate. A permanent alteration in
7 both learning ability and activity resulting from exposures early in life is a health hazard whose
8 significance to humans should be pursued further.
9 Neurophysiological effects from exposure. to diesel exhaust were investigated in rats by
10 Laurie and Boyes (1980, 1981). Rats were exposed to diluted diesel exhaust containing 6 mg/m 3
11 · DPM for 8 hi day, 7 days/week from birth up until28 days of age. Somatosensory evoked
12 potential, as elicited by a 1 rnA electrical pulse to the tibial nerve in the left hind limb, and visual
13 evoked potential, as elicited by a flash of light, were the end points tested. An increased pulse
14 latency was reported for the rats exposed to diesel exhaust, and this was thought to be caused by .
15 a reduction in the degree of nerve myelinization. There was no neuropathological examination,
16 however, to confirm this supposition.
17 Based on the data presented, it is not possible to specify the particular neurological
18 impairment(s) induced by the exposure to diesel exhaust. Again, these results occurred following
19 exposure to a high level of diesel exhaust and no additional concentration-response studies were
20 performed.
21
22 5.1.2.3.11. Effects on reproduction and development. Studies of the effects of exposure to
23 diesel exhaust on reproduction and development are summarized in Table 5-14. Twenty rats
24 were exposed 8 h/day on days 6 thfough 15 of gestation to diluted diesel exhaust containing 6
25 mg/m 3 DPM (Werchowski et al., 1980a,b; Pepelko and Peirano, 1983). There were no signs of
26 maternal toxicity or decreased fertility. No skeletal or visceral teratogenic effects were observed
27 in 20-day-old fetuses (Werchowski et al., 1980a). In a second study, 42 rabbits were exposed to
28 6 mg/m 3 DPM for 8 hlday, on gestation days 6 through 18. No adverse effects on body weight
29 gain or fertility were seen in the does exposed to diesel exhaust. No visceral or skeletal
. 30 developmental abnormalities were observed in the fetuses (Werchowski et al., 1980b).
31 Pepelko and Peirano (1983) evaluated the potential for diesel exhaust to affect
32 reproductive performance in mice exposed from 100 days prior to exposure throughout maturity
33 of the F 2 generation. The mice were exposed for 8 h/day, 7 days/week to 12 mg/m 3 DPM. In
34 general, treatment-related effects were minimal. Some differences in organ and body weights
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