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

1 definitive conclusions as to the. cause of any noncarcinogenic diesel exhaust effect, observed or
2 reported.
3
4 5.6.2. Effects of Diesel Exhaust on Laboratory Animals
5 Laboratory animal studies of the toxic effects of diesel exhaust have involved acute, sub-
6 chronic, and chronic exposure regimens. In acute exposure studies, toxic effects appear to have
7 been associated primarily with high concentrations of carbon monoxide, nitrogen dioxide, and
8 aliphatic aldehydes. In short- and long-term studies, toxic effects have. been associated with
9 exposure to the complex exhaust mixture. Effects of diesel exhaust in various animal species are
1 0 summarized in Tables 5-2 to 5-14. In short-term studies, health effects are not readily apparent,
11 and when found, are mild and result from concentrations of about 6 mg/m 3 DPM and durations of
12 exposure approximating 20 h/day. There is ample evidence, however, that short-term exposures
13 at lower levels of diesel exhaust affect the lung, as indicated by an accumulation ofDPM,
14 evidence ofinflarnmatory response, AM aggregation and accumulation near the terminal
15 bronchioles, Type II cell proliferation, and the thickening of alveolar walls adjacent to AM
16 aggregation. Little evidence exists, however, from short-term studies that exposure to diesel
17 exhaust impairs lung function. Chronic exposures cause lung pathology that results in altered
18 pulmonary function and increased DPM retention in the lung. Exposures to diesel exhaust have
19 also been associated with increased susceptibility to respiratory tract infection, neUrological or
20 behavioral changes, an increase in banded neutrophils, and morphological alterations in the liver.
21
22 5.6.2.1. Effects on Survival and Growth
23 The data presented in Table 5-3 show limited effects on survival in mice and rats and
24 some evidence of reduced body weight in rats following chronic exposures to concentrations of ·
25 · 1.5 mg/m 3 DPM or higher and exposure durations of 16 to 20 h/day, 5 days/week for 104 to 130
26 weeks. Increased lung weights and lung to body weight ratios in rats, mice, and hamsters; an
27 increased heart to body weight ratio in rats; and decreased lung and kidney weights in cats have
28 been reported following chronic exposure to diesel exhaust. No evidence was found of an effect
29 of diesel exhaust on other body organs (Table SA). The lowest-observed-effect level in rats
30 approximated 1 to 2 mg/m 3 DPMfor 7 h/day, 5 days/week for 104 weeks.
31
32 5.6.2.2. Effects on Pulmonary Function
33 Pulmonary function impairment has been reported in rats, hamsters, cats, and.monkeys·
34 exposed to diesel exhaust and included lung mechanical properties (compliance and resistance),
35 diffusing capacity, lung volumes, and venti!atory performance (Table 5-5). The effects generally
36 . appeare4 only after prolonged exposures. The lowest exposure levels (expressed in terms of
2/1/98 5-83 DRAFT --DO NOT CITE OR QUOTE