Acute toxicity of gasoline and ethanol automobile engine exhaust gases

Toxicology Letters, 26 (1985) 187-192

187

Elsevier

TOXLett.

1443

ACUTE TOXICITY ENGINE EXHAUST (Comparative

OF GASOLINE GASES

toxicity

of engine

EDUARDO

MASSAD,

CARMEN

RUBERVAL

DA SILVA,

PAUL0

Laboratory

of Experimental

Dr. Arnaldo,

AND ETHANOL

fuels;

DIVA HILARIO

ethanol

exhaust

fumes)

SALDIVA,

LUIZA

MARIA

NASCIMENTO

Air Pollution,

AUTOMOBILE

School

SALDIVA

of Medicine,

NUNES

CARDOSO,

and GYGRGY

M. BiiHM*

University of So

Paula,

Av.

455 - CEP 01246, S-0 Paul0 (Brazil)

(Received

September

28th,

(Accepted

May 24th,

1985)

1984)

SUMMARY A comparative gasoline Wistar

inhalation

and ethanol

engine

rats housed

of carbon

(CO)

relative humidity

and the environment.

the ethanol-fuelled

and

study was performed

to investigate

the potential

health

effect of

fumes.

chambers gasoline

were exposed to test atmospheres and

ethanol

and flow rate were monitored

The dilution

The LCsas for 3-h exposures the acute toxicity,

exhaust

in inhalation

monoxide

temperature,

exposure

method

exhaust

continually

gave a concentration

were determined

fumes within

for the 3 test atmospheres.

in terms of LC 50r of the gasoline-fuelled

of various

diluted to control

with

concentrations air.

CO

level,

the gas concentration

1.0% of the target. The results demonstrated

engine was significantly

higher

that

than that of

engine.

INTRODUCTION

The substitution of gasoline by ethanol as an automobile fuel in Brazil aroused considerable discussion about the impact of exhaust emissions on ambient air quality and the effects on public health. We started experimental work to assess the biological consequences of this policy in 1980 [ 1, 21. Considering that the stationary situation is the most acutely toxic, the lethal concentration for 50% of the sample (LCSO) for the exhaust fumes of unloaded and stationary engines was determined. The expectation was that the acute exposure of

* To whom

0378-4274/85/$

correspondence

03.30

should

0 Elsevier

be addressed

Science

Publishers

B.V.

188

animals to a wide range of concentrations potential human response to acute hazards MATERIALS

would provide some due to the new fuel.

insight

into

the

AND METHODS

4 Groups of 20 Wistar rats, weighing 19Ok22 g, were used in each of 3 test atmospheres: ethanol exhaust gas, gasoline exhaust gas and a CO control, all diluted with clean air. During the exposure period, the animals were housed in aluminum 115-l inhalation chambers. Single lots of ethanol and gasoline were used to ensure homogeneity of exhaust composition. The ethanol used as fuel was 96” proof, with 99% purity. The gasoline was unleaded, with an octane rating of 73 (Motor Method). The CO (White and Martins) was bottled, in a nominal concentration of l.O+ 0.3% by vol. The ethanol and gasoline exhaust fumes were generated by 2 new, previously unused, Fiat engines of 1300 cm3 displacement, operating unloaded with a cylinderhead temperature of 97 f 10°C and an outlet exhaust gas temperature of 100 + lO”C, as measured by thermocouples, in the stationary mode at a constant speed of 1000 rev./min. This speed was selected as it gave experimental results of greater consistency than the recognized value of 750 rev./min for the stationary mode. Steady-state operation was selected, since it permits better definition and control of the physical and chemical properties of the gases, and simulates the most hazardous situation in practice. The emission mode was fixed at 2.0% CO for both engines, although the levels of this gas in the gasoline exhaust would be 1.5 times higher under normal operating conditions, according to the manufacturer. On the other hand, it has been shown

TABLE

1

DOSE-RESPONSE

RESULTS

_~

Atmosphere

CO dose (ppm)

Log dose

% Response

CO

2025

3.30643

0.20

2050

3.31275

2100

3.32222

0.45 0.55

2162

3.38486

0.70

Gasoline

exhaust

exhaust

rate

1838

10.88

3.26435

0.10

1995

10.03

3.27761

0.60

2000

10.00 9.54

3.30103

0.55

3.32160

0.90

2097 Ethanol

Dilution

2007

9.97

3.30255

0.40

2087

9.58 9.12 8.97

3.31952 3.34084 3.35698

0.50 0.90 0.75

2192 2275

189

that the level adopted

for the gasoline

engine

in terms of fuel consumption [3]. 2 CO analyzers were used, one monitoring

in our studies is the most appropriate the CO concentration

in the engine ex-

haust pipe (Sun, EPA-73) and the other the CO inside the inhalation chambers (Hartmann and Braun, Uras-2t). This analyzer was on-line with a microcomputer (DEC, PDP 1 l/03). The ratio of the concentrations read by the 2 CO monitors gave the dilution rate (Table I). The gas conduction lines were insulated to ensure a temperature of approx. 9O”C, to keep the gases at typical exhaust-pipe temperature until being rapidly diluted with clean air near the top of the chamber, which caused the temperature to drop to approx. 35°C. The ambient temperature was maintained at 20+2”C. Relative humidity and gas flow rate were also controlled during the experiment, to ensure that each group of animals experienced the same environmental conditions, except for the test atmospheres. The ranges of relative humidity and flow rate were set at 60t 20% and 15.5 to.5 l/min, respectively. RESULTS

Dose-response

data

are shown

model

in these experiments:

Yij =

olj

+

in Table

I. We adopted

the following

statistical

(1)

6 Xij

where: = probit of the expected Pij; (Y and 0 = unknown parameters; = log10 of the ith dose of the jth atmosphere; Xij i = i, . . . . kj; j = 1,2,3

Yij

The parameters of the model (1) were estimated by the probit analysis method [5]. The observed value of the xi statistics with 6 degrees of freedom, appropriated to the linearity test of the 3 dose-response curves, is: xi

= 7.28

This is not significant at the 5% level, hence the hypothesis of linearity of the doseresponse curves cannot be rejected. The value of the x$ statistics, with 2 degrees of freedom to the parallelism test is: &

= 4.17

This is not significant

at the 5% level.

190

TABLE

II

ESTIMATES

OF THE PARAMETERS

OF THE

MODEL

(1)

Estimated

Test atmosphere

equation

Gasoline

Y = -

103.5505

+ 32.954 X

Ethanol

Y =

104.3183

+ 32.954 X

co

Y = ~ 104.4346

+ 32.954 X

-

Therefore, the model (1) is appropriate for the analysis of our experiments. Estimates of the parameters of the model (1) are given in Table II. Considering the estimated straight lines for ethanol and gasoline (Table II), we estimated the log LCsO and constructed the confidence interval for this parameter with a coefficient of 0.95. Calculating the antilogarithms of these estimations, we obtained estimates and confidence intervals for the L&O of the test atmospheres (Table III). DISCUSSION

These experiments demonstrate that the acute toxicity of the exhaust of the gasoline-fuelled engine is greater than that of the ethanol-fuelled engine; the higher LCSO value of ethanol exhaust fumes indicates a lower acute toxicity (Table III). An interesting point is the superposition of the confidence intervals of the CO and ethanol LC~O values, showing an equality of both gaseous mixtures and suggesting that the acute effects of ethanol exhaust gases depend mainly on their CO content. Gasoline and ethanol exhaust fumes are complex gaseous mixtures containing CO (an important common component) and many other substances. By comparing their acute toxicity based on CO levels, we have attempted to appraise, indirectly, the other components which may or may not be common to both types of exhaust gases. Therefore, one of the main conclusions of this work is that gasoline exhaust fumes contain noxious substances other than CO, which are responsible icity. This does not seem to be true for ethanol exhaust fumes,

for its greater toxat least in the case

of acute toxicity. In addition to the higher emission rate of CO in the gasoline exhaust fumes, which was intentionally equalized in our experiments, there are some important points

TABLE

III

L&o AND CONFIDENCE

INTERVAL

OF THE TEST ATMOSPHERES Confidence

interval

Test atmosphere

I-C50

Gasoline

1967.8863

[1940.4390-1991.59031

Ethanol

2076.3473

co

2093.1483

[2041.7379-2101.8417] [2067.7594-2120.8014]

(rvm)

(y = 0.95)

191

regarding the qualitative and quantitative differences between ethanol and gasoline exhaust [6-g]. For example, there are high levels of aldehydes in ethanol exhaust which are almost absent in gasoline; relatively high concentrations of sulphur oxides in gasoline which are practically nonexistent in ethanol; important qualitative differences in the emitted hydrocarbons; and the carcinogenetic properties of gasoline, which are apparently absent from ethanol exhaust gases [lo]. Thus, the toxicity differences shown in our experiments, in which CO emissions were equalized, may be explained by the substances that are not common quantitatively of qualitatively to both engine exhausts. This matter is discussed in another paper concerning the chronic effects of gasoline and ethanol gases [lo]. Although it is hazardous to extrapolate from data obtained in experimental models to real situations affecting humans, these results plus the known levels of CO in gasoline emissions indicate that, at least considering traffic congestion, tunnels, garages and other potentially toxically intense conditions, ethanol cars are apparently less dangerous than gasoline-fuelled automobiles. This is a very important point for petroleum-dependent countries, like Brazil and others, which are exploring renewable sources of energy. ACKNOWLEDGEMENTS

This work was realized with grants from FAPESP (75/1200), CNPq (400721/81), STI-MIC (110/82) and HCFMUSP. REFERENCES

1 G.M.

BGhm, E. Massad,

Caldeira fumes,

P.H.

and D.F. Caiheiros, in A.N.

Nayes,

Saldiva,

M.A. Gouveia,

Comparative

toxicity

R.C. Schnell and T.S. Miya (Eds.),

Toxicology, Efsevier, Amsterdam, 2 M.A. Gouveia, C.A.G. Pasqualucci, tion by ethanol 3 2. Linke,

emission,

de veiculo

Automotiva,

Finney,

Statistical

Finney,

Probit

Brasilia, Method

and gasoline Development

1983, pp. 479-482. P.H. Saldiva and G.M. J. Pathol.,

Neto and W. Weishampt,

de carbon0

Engenharia 4 D.J.

car exhaust

I. Cotaite

mon6xido

C.A. Pasqualucci,

of alcohol

M.P.R. exhaust

L.M.N.

in Science and Practice

B(ihm, Pathological

of

aspects of intoxica-

142 (1984) A9.

Efeitos

motor

ciclo Otto,

Brazil,

1983.

in Riological

Cardoso,

fueled automobile

Assay,

da regulagem em regime Charles

da emisdo

de marcha

Griffin,

da [email protected]

lenta,

London

le Simpbsio

de de

and High Wycombe,

1978. 5 D.J.

6 M. Matsuno, Itoh,

Alcohol

7 K. Oblander Engines,

Analysis,

Y. Nakano, engine

emission,

and J. Abthoff,

Daimler-Benz

Press,

8 R.L. Furey and M.W. Jackson, with ethanol-gasoline Washington,

blends,

DC, 1977.

Cambridge

H. Kachi,

University

K. Kimura,

Proc.

111 Int. Symp.

The Influence Stuttgart, Exhaust Proc.

Press,

Cambridge,

F. Tsuruga, Alcohol

of Methanol

1971.

N. lwai, H. Suto, H. Enokido Fuels Technol.,

and Ethanol

California,

and T. 1979.

in the Pipe Composition

of

1981. and evaporative

XII Intersociety

emissions Energy

from a Brazilian

Conversion

Chevrolet

Engineering

fueled

Conference,

192

9 N. Nefussi,

J.V. Assunqlo,

M.P. Toledo

de veicufos a &lcool e a gasolina, taleza,

Brazil,

10 E. Massad, Calheiros, gases,

Castelli,

Brasileiro

Comparaq$o de Engenharia

entre emissdes de poluentes Sanitkia

e Ambiental,

For-

1981.

P.H.N.

Saldiva,

C.D. Saldiva,

R. Silva and G.M.

Environ.

and AS.

XI Congress0

Res., in press.

M.P.R.

BGhm. Toxicity

Caldeira,

of prolonged

L.M.N. exposure

Cardoso, to ethanol

A.M.E.

Moraes,

and gasoline

D.F.

exhaust