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

1 thoracic area at subsequent times. The biological half-life of the iron oxide deposited in the rats'
2 lungs was nearly twice that of controls.
3 Heinrich also used labeled iron oxide aerosols to study clearance in rats exposed to 0.8,
4 2.5, or 7 mg/m 3 diesel DPM for 24mo (Heinrich et al., 1995). Clearance measurements were
5 carried out at 3, 12, and 18 mo of exposure. Half-times of clearance were increased in a
6 concentration- and duration-related way in all exposed groups, with a range of a 50% increase in
7 the 0.8 mg/m 3 group at 3 mo to an 11-fold increase in the? mg/m 3 group at 19 mo. The
8 differential cell counts in these animals were stated to have shown clea.r effects in the 2.5 and 7
9 mg/m 3 groups, but specific information about the changes is not reported.
10 Wolff et al. (1987) investigated alterations in DPM clearance from the lungs of rats
11 chronically exposed to diesel exhaust at 0, 0.35, 3.5, or 7.0 mg/m 3 DPM for 7 hlday, 5 days/week
12 for up to 24 mo. Progressive increases in lung burdens were observed over time in the 3.5 and
13 7.0 mg/m 3 exposure groups. Levels of DPM in terms of milligrams per lung were 0.60, 11.5, and
14 20.5 after 24 mo of exposure at the 0.35, 3.5, or 7.0 mg/m 3 exposure levels, respectively. There
15 were significant increases in 16-day clearance half-times of inhaled radio labeled particles of
16 · 67 Ga 20 3 (0.1 IJ.m MMD) as early as 6 moat the 7.0 mg/m 3 level and 18 moat the 3.5 mg/m 3
17 level; no significant changes were seen at the 0.35 mg/m 3 level. Rats inhaled fused
18 aluminosilicate particles (2 1-1m MMAD) labeled with 134 Cs after 24 mo of diesel exhaust
19 exposure; long-term clearance half-times were 79, 81,264, and 240 days for the 0, 0.35, 3.5, and.
20 7.0 mg/m 3 groups, respectively. Differences were significant between the control and the 3.5 and
21 7.0 mg/m 3 groups (p < 0.01).
22 Mauderly et al. ( 1987b) compared the effects of diesel exhaust in the developing lung to
23 the adult lung by exposing groups of male F344 rats to3.5 mg/m 3 for 7 hlday, 5 days/week for 6
24 mo. One group (adult) was exposed between 6 and 12 mo of age, and the other was exposed
25 beginning in utero and until 6 mo of age. Clearance of an inhaled monodisperse 2 IJ.m
26 aluminosilicate particle was measured after exposure for 6 mo. The clearance half-time of the
27 slow phase was found to be doubled in adult rats compared with age-matched controls and was
28 · not significantly affected in developing rat lungs.
29 Mauderly et al. compared the effects of diesel exhaust in normal lungs with rats in which
30 emphysema had been induced experimentally by instillation of elastase 6 weeks before diesel
31 exhaust exposures. The rats were exposed to 3.5 mg/m 3 DPM for 7 h/day, 5 days/week for 24
32 mo. Measurements included histopathology, clearance, pulmonary function, lung lavage, and
33 immune response. In the rats that were not pretreated with elastase, there was a significant
34 · reduction in the number of macro phages recovered by pulmonary lavage in contrast to the
35 increases in macrophages reported by Strom (1984) and Henderson et al. (1988). The half-time
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