Pulmonary function changes in Chinese hamsters exposed six months to diesel exhaust

Environment International, Vol. 5, pp. 369- 371, 1981 Printed in the USA. All rights reserved.

0160-4120/81/040369-03502.00/0 Copyright ':~1982 Pergamon Press Ltd.

PULMONARY FUNCTION CHANGES IN CHINESE HAMSTERS EXPOSED SIX MONTHS TO DIESEL EXHAUST Alien Vinegar and Arch Carson Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio 45267, USA

William E. Pepelko Health Effects Research Laboratory, U. S. Environmental Protection Agency, Cincinnati. Ohio 45268 USA

Chinese hamsters were exposed for eight hours per day to automotive diesel exhaust emissions which were diluted with air (18 to I) and had a particulate level of 6.4 m g / m 3. Pulmonary function measurements were made after six months exposure. Body weight (BW), lung weight (LW), vital capacity (VC), residual volume by water displacement (RV,,.) and by gas dilution (RVo), alveolar volume (VA), and carbon monoxide transfer factor (DLCO) were measured. LW showed a significant increase in the diesel exposed animals ( P < 0.01 ) while VC, RVw, and DLCO showed decreases ( P < 0.01 ). Static deflation volumepressure curves showed depressed deflation volumes for diesel exposed animals when volumes were corrected for body weight and even greater depressed volumes when volumes were corrected for lung weight. However, when volumes were expressed as percent vital capacity, the diesel exposed animals had higher lung volumes at 0 and 5 cm H20. Results of the pathological examination of the lung tissue will be necessary for final analysis of our findings. However, preliminary interpretation indicates possible emphysematous changes which are compatible with the observed decrease in DLCO.

Introduction

The present study was designed to evaluate the effects of 6 months exposure to a concentration of diesel exhaust containing 6 m g / m 3 particulate upon pulmonary function in the Chinese hamster.

The effects of exposure to diesel exhaust upon the lungs cannot be accurately predicted from the results of previous studies using either individual pollutants or whole emissions from gasoline engines. A portion of the gaseous pollutants, for example, are adsorbed onto the surface of the particulate matter (Stokinger, 1973), altering both the depth of penetration (Task Group on Lung Dynamics, 1966) and residence time in the lungs (Creasia et al., 1971). There is also little information concerning the composition of sulfates present in diesel exhaust. Certain sulfates, such as zinc ammonium sulfate, have been found to be considerably more irritating than sulfuric acid, the primary form in catalyzed automobile exhaust (Amdur, 1970). Finally, diesel exhaust contains a wide range of both aliphatic and aromatic compounds, the concentration of which, and even the chemical structure, are not well defined (Karasek et al., 1974).

Methods General procedure Adult male Chinese hamsters were exposed to diesel exhaust eight hours per day, seven days per week at a dilution ratio of approximately 1:18. Particulate concentration averaged 6.4 m g / m 3. The animals were exposed in stainless steel wire cages 11 inches square. Nine or ten animals were housed per cage. Food and water were provided ad libitum. Total length of exposure was 6 months. Following completion of exposure, the animals were removed, weighed, and body temperature measured via rectal probe. The hamsters were then 369

370

A. Vinegar, A. Carson, and W. E. Pepelko

anesthetized with pentobarbital sodium administered intraperitoneally. The trachea was exposed and cannulated just below the glottis. Vital capacity The animal was placed in the supine position on an insulated platform and the tracheal cannula was attached to the breathing port of the DLCO apparatus (see Fig. 1). The animal was hyperventilated, with the respiratory valve in the B position, for a period sufficient to produce apnea lasting 10-15 sec. With the valve in position A fresh air was injected into the lungs of the animal from a calibrated syringe until the pressure in the airway plateaued at +25 cm H20. The volume reached was defined as total lung capacity (TLC). Air was then withdrawn into the syringe until the pressure in the airway plateaued at - l 0 cm H20. The volume reached was defined as residual volume (RV). The corrected difference between the two syringe readings was defined as vital capacity (VC). The animal was immediately returned to breathing fresh air. A lveolar volume The animal was again hyperventilated until apnea was produced. The valve was turned to the C position allowing the lungs to be deflated to RV. The valve was turned to the D position allowing the lungs to be inflated quickly to TLC with air containing a known quantity of the inert gas neon. The valve was turned to

PRESSURE TRANSDUCER

)EADSPACE SYRINGE

TAL CAPACITY SYRINGE ,

SYRINGE

~ SYRINGE MIXING

the E position and the gas in the lungs was pumped in and out ten times to facilitate even distribution of the neon within the lungs. The valve was turned to the F position allowing passive expiration of about one-third of the vital capacity into a preset ground glass syringe, effectively eliminating the anatomical and mechanical deadspace air. The remaining alveolar air could then be sampled into a gas-tight chromatography syringe for analysis. The animal was returned to breathing fresh air. DLCO The animal was hyperventilated until apnea was produced. The valve was turned to the C position allowing deflation of the lungs to RV. The valve was then turned to the D position allowing rapid inflation of the lungs to TLC with air containing known amounts of neon and carbon monoxide. Approximately 8-10 sec after inflation, the valve was turned to the F position and the alveolar gas sampled as described above. During all of the above procedures, the body temperature was monitored and an attempt made to keep it as close to the preanesthesia level as possible by use of a variable intensity heat lamp mounted above the platform. The procedures and calculations for determination of DLCO, alveolar volume and vital capacity as described above are modified from those reported by O'Neil et al. (1977). Static deflation volume-pressure curves The lungs were exposed by opening the chest cavity and retracting the ribs. The lungs were connected in parallel, by way of the tracheal cannula, to a syringe and a pressure transducer. Pressure was monitored on an oscilloscope and volume read directly from the syringe. The lungs were given a known volume history by inflating twice from 0 to 30 cm H20, maintaining for 5 sec, and then deflating in increments of five cm H20, and maintaining at each subsequent pressure for 15 sec. Deflation was taken to - 1 0 cm H20. Volumes were recorded at each pressure decrement. Final lung treatment The lungs were then removed and attached to a pressure reservoir at - 1 0 cm H20. Lung weight and displacement volume were determined. This volume was defined as residual volume (RVw) as compared with the abovementioned determination by gas dilution (RV D). Finally, the lungs were instilled with 10% buffered formalin and maintained at 30 cm H20 while submerged in a bath of the same fixative. After 36 to 48 h they were stored in individual jars of buffered formalin to await preparation for pathological examination.

VACUUM

Results

Fig. I. DLCO apparatus schematic.

Our preliminary results are presented in Table 1 and Fig. 2. The apparent difference in RV, as determined by water displacement, may not be real since correction

371

Pulmonary_ function changes Table 1. Effects of diesel exhaust exposure upon pulmonary function parameters in Chinese hamsters. Body Weight (g)

Lung Weight (rag)

X S.D. N

36.0 4.1 9

227 22 9

X S.D. N T

35.2 3.4 10 NS

374 55 10 P<0.01

% VC

6.35 0.54 9

VC/BW (mL/g)

RV w (mL)

RV D VA (mL) (mL)

DLCO

DLCO/V A

Control 0.0268 4.25 0.0038 0.60 9 9

0.319 0.131 8

0.36 0.18 5

1.17 0.31 5

0.0029 0.0011 9

0.0027 0.0005 9

Diesel 0.0217 2.07 0.0046 0.54 10 10 P < 0 . 0 5 P<0.01

0.016 0.025 9 P<0.01

0.40 0.13 8 NS

1.16 0.0015 0.17 0.0008 8 10 NS P<0.01

0.0015 0.0006 10 P<0.01

0.96 0.10 9

10.62 1.17 10 P<0.01

0.75 0.12 10 P<0.01

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LW/BW (rag/g)

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weight, and (D) lung volume corrected for lung weight. Where differences between diesel and control animals exist at least at the P = 0.05 level this is indicated with an asterisk.

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Discussion

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Pathological investigation of the lung tissue has not yet been performed. However, the elevated lung volumes at 0 and 5 cm H20 for the volume-pressure curve where volume is expressed as %VC indicate a possible emphysematous condition in the diesel exposed animals. This is consistent with the significantly reduced DLCO found in these same animals. Exposure at the same concentration for longer periods of time and exposure at higher concentrations may be necessary to more carefully evaluate the potential effects of exposure to diesel exhaust on lung function. References

CM H 2 0

Fig. 2. Static deflation pressure volume curves. Controls are indicated by circles and diesel exposed are indicated by triangles. Asterisks indicate significance at least at the P = 0.05 level.

was not made for tissue density. The diesel exposed animals had lungs that were mainly coal black in color. The added density of the deposited material made the lungs denser, but without knowing the weight and density of deposited material a total correction for lung density cannot be made. The static deflation volumes, Fig. 2 are plotted graphically against pressure in four different ways: (A) percent vital capacity, (B) absolute volume of air removed from lung, (C) lung volume corrected for body

Amdur, M. O. (1970) The impact of air pollutants on physiologic response of the respiratory tract, Proc. Am. Philosophical Soc. 14, 3-8. Creasia, D. A., Poggenburg, J. L., and Nettesheim, P., Jr. (1976) Elution of benzo(a )pyrene from carbon particles in the respiratory tract of mice, J. ToxicoL Environ. Health 1, 967-975. Karasek, F. W., Smythe, R. J., and Laub, R. J. (1974) A chromatographic-mass spectropholometric study of organic compounds adsorbed on particulate matter from diesel exhaust, J. Chromatogr. 101, 125-136. O'Neil, J. J., Takezawa, and Crapo, J. D. (1977) Pulmonary diffusing capacity: Single breath measurements compared to morphometric analysis in rats exposed to NO 2 and 02, The Physiologist 20, 69. Stokinger, H. E. (1975) Toxicology of diesel emissions, in Proceedings of the symposium on use of diesel-powered equipment in underground mining. IC 8666. Bureau of Mines, U. S. Dept. Interior, Washington, DC. Task Group on Lung Dynamics (1966) Deposition and retention models for internal dosimetry of the human respiratory tract, Health Phys. 12, 173-207.