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

1 effects occur at lower doses than tumor induction does in the rat, and because these effects may
2 be cofactors in the etiology of diesel exhaust-induced tumors, noncancerous pulmonary effects
3 must be considered in the total evaluation of diesel exhaust, notably the particulate component.
4
5 5.6. SUMMARY AND DISCUSSION
6 5.6.1. Effects of Diesel Exhaust on Humans
7 The most readily identified acute noncancer health effect of diesel exhaust on humans is
8 its ability to elicit subjective complaints of eye, throat, and bronchial ir.ritation and
9 neurophysiological symptoms such as headache, lightheadedness, nausea, vomiting, and
1 0 numbness and tingling of the extremities. Studies of the perception and offensiveness of the odor
11 of diesel exhaust and a human volunteer study in an exposure chamber have demonstrated that .
12 the time of onset of the human subjective symptoms is inversely related.to increasing
13 concentrations of diesel exhaust and the severity is directly related to increasing concentrations of
14 diesel exhaust. In one study in which a diesel engine was operated under varying load
15 conditions, a dilution factor of 140 to 475 was needed to reduce the exhaust level to an odor-
16 detection threshold level.
17 A public health issue is whether short-term exposure to diesel exhaust might result-in an
18 acute decrement in ventilatory function and whether the frequent repetition of such acute
19 respiratory effects could result in chronic lung function impairment. One convenient means of
20 studying acute decrements in ventilatory function is to monitor differences in pulmonary function
21 in occupationally exposed workers at the beginning and end of a workshift. In studies of
22 underground miners, bus garage workers, dock workers, and locomotive repairmen, increases in
·23 respiratory symptoms (cough, phlegm, and dyspnea) and decreases in lung function (FVC, FEV 1 ,
24 PEFR, and FEF 25 _ 75 ) over the course of a workshift were generally found to be minimal and not
25 statistically significant. In a study of acute respiratory responses in diesel bus garage workers,
26 . there was an increased reporting of cough, labored breathing, chest tightness, and wheezing, but
27 no reductions in pulmonary function were associated with exposure to diesel exhaust.
28 Pulmonary function was affected in stevedores over a workshift exposure to diesel exhaust but
29 normalized after a few days without exposure to diesel exhaust fumes. In a third study, there was ·
30 a trend toward greater ventilatory function changes during a workshift among coal miners, but
31 the decrements were similar in miners exposed and not exposed to diesel exhaust.
32 Smokers appeared to demonstrate larger workshift respiratory function decrements and
33 increased incidents of respiratory symptoms. Acute sensory and respiratory symptoms were
34 earlier and more sensitive indicators of potential health risks from diesel exposure than were
35 decrements in pulmonary function. Studies on the acute health effects of exposure to diesel
36 exhaust in. humans, experimental and epidemiologic, have failed to demonstrate a consistent
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