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

1 5.6.2.6. Other Noncancerous Effects
2 Essentially no effects (based on the weight of evidence of a number of studies) were
3 noted for reproductive and teratogenic effects in mice, rats, rabbits, and monkeys; clinical
4 chemistry and hematology in the rat, cat, hamster, and monkeys; and enzyme induction in the rat
· 5 and mouse (Tables 5-10 through 5-12 and 5-14).
6
7 5.6.3. Comparison of Filtered and Unfiltered Diesel Exhaust
8 The compariso!l of the toxic responses in laboratory animals exposed to whole diesel
9 exhaust or filtered exhaust containing no particles demonstrates across laboratories that diesel
1 0 particles are the principaf etiologic agent of noncancerous health effects in laboratory animals
11 exposed to diesel exhaust (Table 5-15). Whether the particles act additively or synergistically
12 with the gases cannot be determined from the designs of the studies. Under equivalent exposure
13 regimens, hamsters have lower levels of retained DPM in their lungs than rats and mice do and
14 consequently less pulmonary function impairment and·pulmonary pathology. These differences
15 may result from a lower intake rate ofDPM, lower deposition rate and/or more rapid clearance
16 rate, or lung tissue that is less susceptible to the cytotoxicity of DPM. Observations of a
17 decreased respiration in hamsters when exposed by inhalation favor lower intake and deposition
18 rates.
19
20 5.6.4. Interactive Effects of Diesel Exhaust
21 . There is no direct evidence that diesel exhaust interacts with other substances in an
22 exposure environment, other than an impaired resistance to respiratory tract infections. Young
23 animals were not more susceptible. In several ways, animals with laboratory-induced
24 emphysema were more resistant. There is experimental evidence that both inorganic and organic
25 compounds can be adsorbed onto carbonaceous particles. When such substances become
26 affiliated with particles, these substances can be carried deeper into the lungs where they might
27 have a more direct and potent effect on epithelial cells or on AM ingesting the particles. Few
28 specific studies to test interactive effects of diesel exhaust with atmospheric contaminants, other
29 than coal dust, have been conducted. Coal dust and DPM had an additive effect only.
30
31 5.6.5. Summary
32 The principal noncancerous health hazard to humans from exposure to diesel exhaust is a
33 structural, functional, or biochemical injury to the lung. Current knowledge indicates that the
34 carb_onaceous core of the diesel particle is the prime c;ausative agent of lung injury. The limg
35 injury appears to be mediated by a progressive impairment of AMs. Because noncancerous
36 pulmonary effects occur at lower doses than those inducing tumors in rats and appear to be
211/98 5-86 DRAFT--DO NOT CITE OR QUOTE