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TOXICOLOGYANDAPPLIEDPHARMACOLOGY 61,368-377 1981)

Comparative Short-Term Inhalation Toxicity of Ethylene Glycol

Monomethyl Ether and Propylene Glycol Monomethyl Ether

in Rats and Mice

R. R.

MILLER, J. A. AYRES, L. L. CALHOUN, J. T. YOUNG, AND

M. J.

MCKENNA

Toxicology Research Laboratory, Health and Environmental Scie nces , USA.

Dow Chem ical U SA, Midland, Michigan 48640

Received April 20, 1981; accepted July 27. 1981

Comparative Short-Term Inhalation Toxicity o f Ethylene Glycol Monomethyl Ether and

Propylene Glycol Monomethyl Ether in Rats and Mice.

MILLER, R. R., AYRE S, J. A., CAL-

HOUN, L. L., YOUNG, J. T., AND MCKENNA, M. J., (1981). Toxic01 Appl. Pharmacoi. 61,

368-377. Male and female Fischer 344 rats and B6C3Fl mice were exposed to 0, 100, 300,

or 1000 ppm ethylene glycol monomethyl ether (EGME) or to 0, 300, 1000, or 3000 ppm

propylene glycol monomethyl ether (PGME) 6 hr/day for a total of 9 days during an 1 -day

interval. Although structural ly similar, the biological activit ies of the two materials were

dramatically dif ferent. The high concentration of EGME (1000 ppm) had pronounced adverse

effect s on body weight gain, peripheral blood counts, bone marrow, testes, and lymphoid

tissues. Similar but less pronounced changes also occurred in some animals in the 300 ppm

EGME group. Exposure to 3000 ppm PGME resulted in increased liver weights in male rats

as well as central nervous system depression and decreases in specific gravity of urine of both

male and female rats. However, there were no gross or histopathologic changes in either rats

or mice which could be attributed to exposure to PGME. Hence the treatment-related changes

which occurred in rats and mice exposed to PGME vapors, even at the highest concentration

(3000 ppm), would constitute, at most, a minimal ef fect . Although PGME and EGME have

comparable vapor pressures, the potential hazard of exposure to PGME vapors appears to be

distinctly less than to EGME vapors.

Ethylene glycol monomethyl ether (EGME; cohols and ethers. Their miscibility with a

2-methoxy-ethanol) and propylene glycol wide variety of organic liquids, as well as

monomethyl ether (PGME; 1-methoxy-2- with water, makes them particularly suitable

propanol) are volatile, colorless liquids which for a multitude of solvent purposes in in-

combine the solubility characteristics of al- dustrial processes and applications.

CH3-0-CH2CHz-OH CH3-0-CH$H-OH

EGME PGME

There have been several documented in- and Wegman, 1978) which have resulted

stances of human overexposure to EGME primarily in hematologic and central nervous

(Donley, 1936; Greenburg et al., 1938; Par-

system disorders.

sons and Parsons, 1938; Zavon, 1963; Ohi A variety of studies with various species

0041-008X/81/150368-10$02.00/0

Copyright 0 1981 by Academic Press, Inc.

All rights of reproduction in any form reserved.

368

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COMPARATIVE TOXICITY OF EGME AND PGME

369

of laboratory animals (Carpenter et al.,

1956; Werner et al., 1943a,b,c) have shown

that exposure to EGME can result in he-

matologi,c disorders similar to those observed

in humans. However, central nervous system

effects as described in humans have appar-

ently not been clearly shown in laboratory

animals exposed to EGME. Atrophy of

testes and degenerative changes in the tes-

ticular germinal epithelium have also been

found in laboratory animals (Wiley et al.,

1938; Nagano et al., 1979) exposed to

EGME.

A substantial toxicologic data base also

exists for PGME as reviewed by Rowe et al.

(1954). Massive oral doses in rats (5 to 7 g/

kg) produce a profound central nervous sys-

tem depression resulting in prostration and

death. Rats given repeated oral doses as high

as 3 g/kg (26 doses during 35 day interval)

had microscopic changes in livers and kid-

neys and moderate increases in weights of

those organs. Inhalation studies in which

rabbits and monkeys were subjected to 132

exposures of PGME at a level of 800 ppm

over a period of 186 days showed no evidence

of adverse effects as judged by gross ap-

pearance and behavior, growth, final body

and organ weights, hematology, and micro-

scopic examinations of tissues. Similarly,

there were no ill effects by the same criteria

in rats and guinea pigs which received 130

exposures in a 184 day period at a concen-

tration of 1500 ppm. Slight growth depres-

sion, very slight liver and lung effects, and

signs of central nervous system depression

were noted in animals exposed to 3000 ppm

for approximately 6 months. Goldberg et al.

( 1964) found a transient, nonspecific depres-

sion of pole climbing activity of rats for the

first several 4 hr/day exposures to 5000 and

10,000 ppm PGME.

The present report describes the results

obtained in 2-week vapor inhalation stud-

ies in which rats and mice were exposed to

high concentrations of EGME or PGME.

These studies were conducted in order to

update the inhalation toxicological data base

for the two materials.

METHODS

Test materials. EGME was obtained f rom the pro-

duction facilities of Dow Chemical USA, Midland,

Mich. PGME was obtained from the Dow Chemical

USA production facilities at Plaquemine, La. Gas chro-

matographic analyses of the test materials indicated that

EGME was greater than 99% pure, while PGME was

95.8% pure. The PGME sample contained 4% of the

structural isomer 2-methoxy- 1 propanol.

Animals. Male and female Fischer 344 rats (6-8

weeks of age) and B6C3Fl mice (6-8 weeks of age)

were purchased from Charles River Breeding Labora-

tories, Inc. (Portage, Mich.). The animals were individ-

ually identified with metal ear tags, randomly assigned

to control (nontest material exposed) or exposure groups,

and then allowed to acclimate to laboratory conditions

for several days prior to initiating exposures. Both rats

and mice were housed singly in stainless-steel wire mesh

cages, and food (Purina Certified Laboratory Chow

5002, Ralston Purina, St. Louis, MO.) and water were

available ad libitum except during exposures. Temper-

ature and relative humidity in the chambers and in the

animal holding rooms were maintained at approxi-

mately 2 1 C and SO%, respectively, and the light cycle

was regulated at 12 hr light, 12 hr dark.

For EGME studies, each control and exposure group

initially consisted of 5 mice per sex and 10 rats per sex.

Half of the rats (5 per sex) in each group were included

only to assess osmotic red blood cell fragili ty. For

PGME, the control and high exposure groups each ini-

tially contained 10 rats and 10 mice of each sex, while

the intermediate and low exposure groups each con-

tained only 5 rats and 5 mice per sex at the start of the

study. Half of the rats and mice (5 per sex) in the control

and high exposure groups were included in order to as-

sess recovery approximately 6 weeks after exposures

were terminated. Exposure concentrations for PGME

(0,300, 1000, and 3000 ppm) were approximately three-

fold higher than for EGME (0, 100, 300, and

1000 ppm).

Chambers. EGME exposures were conducted in 14.5

m3 walk-in type chambers with epoxy resin-coated floors

and walls and stainless-steel ceilings. Total airflow

through these chambers was maintained at approxi-

mately 2500 liters/min. For PGME, 4.1 m3 stainless-

steel and glass chambers were used, with total chamber

airflow maintained at approximately 600 liters/min.

Vapor generation and analyses. Exposure concentra-

tions of PGME and EGME were generated by vapor-

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370

MILLER ET AL.

izing the liquid test materials at controlled rates with

a J-tube assembly in conjunction with a compressed air

flameless heat torch (130°C) as described by Miller et

al. (1980). The actual concentration of the test materials

in each exposure chamber was measured two to three

times per hour by infrared spectroscopy using a MIRAN

I (Foxboro Co.) infrared gas analyzer. The time-weighted

average (TWA) analytical concentration and nominal

concentration (ratio o f the total amount of liquid va-

porized to the total amount o f air through the chamber)

were calculated for each exposure chamber on a daily

basis. The mean daily TWA analytical concentration

and mean daily nominal concentration for each exposure

chamber were within 5% of the intended target concen-

tration. The exposures were conducted 6 hr/day on 5

consecutive days followed by 4 additional consecutive

days of exposure after a weekend interruption (total of

9 exposures during an 1 -day interval).

Criteria of response. Animals were observed daily for

signs of toxicity or changes in appearance. Body weights

were recorded immediately prior to initiating exposures

and at selected intervals thereafter, as well as imme-

diately prior to sacrif ice. Hematologic parameters in-

cluding packed cell volume (PCV), hemoglobin (Hgb),

red blood cell count (RBC), and total and differential

white blood cell counts (WBC) were performed for each

rat and mouse. In addition, platelet counts were per-

formed for rats exposed to PGME vapors but not

EGME, and osmostic red cell fragili ty was evaluated

by the method of Schalm (1965) on subgroups of rats

exposed to EGME, but not PGME vapors. Clinical

chemistry evaluations on serum samples from rats ex-

posed to EGME, as well as rats and mice exposed to

PGME vapors, included glutamic-pyruvic transaminase

(SGPT) act ivi ty, alkaline phosphatase (AP) act ivi ty,

urea nitrogen (BUN), glucose (Glu), total protein (TP),

albumin (Alb), globulins (Glob), and total bilirubin

(T.Bili). Urinalyses (rats only) included pH, protein,

ketones, bilirubin, urobilinogen, occult blood, and spe-

cific gravitv.

Approximately 18 hr after the final exposure, each

animal was anesthetized with methoxyflurane and de-

capitated after clamping the trachea. Rats (but not

mice) were fasted overnight prior to sacrif ice. Each an-

imal was given a complete gross pathologic examination

by a veterinary pathologist. Weights of liver, kidneys,

heart, thymus, testes, spleen (PGME study only), and

brain (EGME study only) were recorded. Representa-

tive portions of an extensive list of tissues from animals

in the control and high exposure groups were prepared

by conventional histologic methods and examined by

light microscopy. Histopathologic examinations were

not performed for mice in the EGME study. For mice

in the PGME study, only selected tissues were examined

microscopically as deemed appropriate from observa-

tions in rats. Target organs identified in the high ex-

posure groups were also evaluated for animals in the

two lower exposure groups in order to evaluate dose-

response relationships.

Statistics.

Body weights, organ weights, hematology

data, clinical chemistry data, and urinary specific grav-

ity were evaluated by analysis of variance and Dunnett’s

test. The level of significance chosen was p < 0.05.

RESULTS

ody weights

Growth of male and female rats in the

high ( 1000 ppm) EGME group was signif-

icantly retarded (data not shown). The ad-

verse effects on growth of these animals were

apparent after 2 days of exposure. In addi-

tion, the mean body weight gains of female

rats in the 100 and 300 ppm groups were

statistically lower than for controls at the

end of the study, and there was a tendency

toward lower body weight gains for male rats

in the 300 ppm EGME group as well. In

contrast to rats, the growth of mice was not

significantly altered by exposure to EGME

vapors and the growth of neither species was

significantly altered by exposure to PGME

vapors (data not shown).

Organ Weights

The weights of thymus glands of male and

female rats and mice exposed to 1000 ppm

EGME were markedly lower than for con-

trols; similar but less pronounced reductions

of thymus weights also occurred for male

and female rats as well as for female mice

in the 300 ppm EGME group (Table 1).

The absolute and relative testes weights

of male rats and mice in the 1000 ppm

EGME group were also markedly lower than

for controls as a result of exposure to the

test material. All other statistical differences

in absolute or relative organ weights in rats

and mice exposed to EGME were considered

to be reflections of reduced body weight

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MILLER ET AL.

gain, or were sporadic in nature and unre-

lated to treatment.

The mean absolute and relative liver

weights of male rats exposed to 3000 ppm

PGME were statistically significantly higher

than for controls after 2 weeks, probably as

a result of exposure to the test material

(Table 2). In addition, the relative (but not

absolute) liver weights of female rats and

female mice in the 3000 ppm PGME group

were statistically significantly higher than

for controls after 2 weeks.

All other statistically significant differ-

ences in organ weights of PGME-treated

rats and mice after 2 weeks were considered

sporadic in nature or reflections of normal

biologic variability.

For animals sacrificed 6 weeks after ter-

mination of exposure to PGME, the absolute

and relative organ weights of male and fe-

male rats from the 3000 ppm group had re-

turned to normal, and there were no other

organ weight changes in either rats or mice

(data not shown).

Hematology

Packed cell volume (PCV), red blood cell

counts (RBC), hemoglobin (Hgb), and white

blood cell counts (WBC) of male and female

rats in the 1000 ppm EGME group were

statistically lower than for controls (Table

3). Similar changes occurred in male mice

exposed to 1000 ppm EGME, but only the

white blood cell counts of 1000 ppm female

mice were statistically decreased in compar-

ison to controls (data not shown). Of the

various hematologic parameters, the white

blood cell counts of both rats and mice were

most severely altered.

In rats, differential white cell counts in-

dicated a trend toward a lower percentage

of neutrophils and a higher percentage of

lymphocytes with increasing exposure con-

centration (data not shown); no such trends

were apparent in mice.

Some of the hematologic parameters of

rats and mice exposed to 300 ppm EGME

were also statistically lower than for con-

trols, although these alterations were less

severe than at 1000 ppm. The most pro-

nounced hematologic effect at 300 ppm was

the depression in white blood cell counts in

female rats (Table 3). The only hematologic

effect at 100 ppm with possible toxicologic

significance was the statistically significant

but slight depression in white blood cell

counts in male rats.

Osmotic red blood cells fragility of male

and female rats exposed to 1000 ppm EGME

was not significantly different from control

animals (data not shown). Since no effects

were detected in the high EGME exposure

group, red cell fragility was not evaluated

for animals in the two lower exposure groups.

In contrast to the pronounced alterations

in hematologic parameters resulting from

exposure to EGME, there were no treat-

ment-related changes in PCV, RBC, Hgb,

or WBC in animals exposed to PGME (Ta-

ble 3). The mean platelet counts were ele-

vated in rats exposed to PGME (data not

shown) but these changes in platelet counts

were of uncertain toxicologic significance in

view of the variability of this parameter in

control animals. There were no statistically

significant changes in the hematologic pa-

rameters of either male or female mice (data

not shown).

When recovery group animals were sac-

rificed 6 weeks after exposures to PGME

were terminated, platelet counts were nor-

mal and there were no other statistically sig-

nificant changes considered related to ex-

posure.

Clinical Chemistry

Serum total protein, albumin (males only),

and globulin values of male and female rats

exposed to 1000 ppm EGME were statisti-

cally lower than for controls (data not

shown). Similar but less pronounced effects

on these parameters also occurred for male

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COMPARATIVE TOXICITY OF EGME AND PGME

375

and female rats in the 300 ppm EGME

group. All other effects on clinical chemistry

parameters of rats exposed to EGME vapors

were considered to be either spontaneous or

related to nutritional status at the time of

sacrifice (e.g., decreased alkaline phospha-

tase activity and decreased glucose). Clinical

chemistry analyses were not performed for

mice exposed to EGME vapors.

There were no treatment-related changes

in clinical chemistry parameters of male and

female rats or mice exposed to PGME which

were considered to be toxicologically signif-

icant (data not shown), Alkaline phospha-

tase activity was statistically significantly

lower than for controls in male rats in the

300 and 3000 ppm groups as well as in fe-

male rats in all three PGME exposure

groups. However, these depressions in al-

kaline phosphatase activity were probably

related to nutritional status at the time of

sacrifice.

Urinalyses

Specific gravity of urine from male rats

exposed to 1000 ppm EGME was statisti-

cally lower than that for controls (data not

shown). Although not statistically different

from controls, there was a trend toward de-

creased urinary specific gravity in 1000 ppm

exposed female rats as well. However, there

were no apparent effects on any other uri-

nary parameters (pH, protein, sugar, ke-

tones, bilirubin, blood, or urobilinogen) for

male or female rats.

For animals exposed to PGME vapors, the

specific gravity of urine from male rats in

the 1000 and 3000 ppm groups as well as

from female rats in the 3000 ppm group was

statistically lower than controls after 2 weeks

(data not shown). In addition, the pH of

urine from male and female rats exposed to

3000 ppm PGME tended to be higher than

for controls after 2 weeks. These effects on

specific gravity and pH of urine were prob-

ably related to exposure, and may suggest

slight alterations in kidney function. All

urinary parameters for male and female rats

in the PGME recovery groups were within

the normal range and not significantly dif-

ferent from controls after 6 weeks.

Histopathology

Microscopically detectable changes at-

tributable to EGME exposure were present

in all male and female rats in both the 1000

and 300 ppm groups. Changes in the 1000

ppm group included markedly reduced bone

marrow cellularity, severe degeneration of

germinal epithelium in the testes (males),

severe lymphoid depletion in the cortex of

the thymus, and reduced numbers of lym-

phoid cells in the spleen and mesenteric

lymph nodes. In the 300 ppm EGME-ex-

posed groups, all animals had some reduc-

tion in thymic cortical lymphoid cells. (Spleen

and mesenteric lymph nodes were not ex-

amined for animals exposed to 100 and 300

ppm.) No treatment-related changes were

seen in any of the male or female animals

exposed to 100 ppm EGME. Since the gross

lesions were similar in rats and mice, no his-

topathology was performed on mice exposed

to EGME.

The cell types which appeared to be spe-

cifically affected by exposure to relatively

high levels of EGME were the germ cells of

the seminiferous tubules, hematopoietic ele-

ments, and lymphoid cells. The changes in

the testicular germinal epithelium consisted

of diffuse, severe, active degeneration, and

necrosis of all spermatogenic elements. For-

mation of spermatidic giant cells was a

prominent feature in some affected tubules,

while other tubules were lined only by Sertoli

cells. After 2 weeks of exposure, sperm were

still present in the epididymides, but active

spermatogenesis had ceased.

The bone marrow of all 1000 ppm EGME-

exposed animals was also diffusely and se-

verely affected. Both myeloid and erythroid

elements were markedly reduced in number,

8/17/2019 Miller 1981

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376

MILLER ET AL.

and there appeared to be a slight relative

increase in immature cells. Megakaryocytes

were present in decreased numbers and were

smaller than those in unexposed animals.

The lymphoid population of several organs

was depleted or reduced, most severely in the

thymus, but also in the spleen and mesen-

teric lymph nodes. Virtually the entire thymic

cortical lymphoid population was depleted

and only condensed fibrovascular stoma re-

mained in the thymus of top dose animals.

Less dramatic reductions were present in the

lymph nodes which were characterized by

thinner medullary cords and smaller ger-

minal centers. Similarly, in the spleen, ger-

minal centers were just as numerous as in

control animals, but they were smaller. Ev-

idence of active lymphoid necrosis was not

observed in any organ. The areas of the

lymph nodes which were depleted are nor-

mally populated by both B-lymphocytes

(germinal centers) and T-lymphocytes (med-

ullary cords and paracortical regions); con-

sequently, there appeared to be no specificity

for either cell type.

The treatment-related effects on the thy-

mus persisted at the 300 ppm EGME ex-

posure level, although to a much lesser ex-

tent. The spleen and mesenteric lymph nodes

were not examined at the 300 and 100 ppm

concentrations because the thymus, which

was more severely affected, was considered

an adequate indicator of lymphoid organ

toxicity at these intermediate levels.

For rats and mice exposed to PGME va-

pors, histopathologic examinations for male

and female rats and mice revealed no lesions

which could be attributed to exposure to the

test material. Even in the liver, there were

no microscopically detectable changes which

could account for the statistically significant

increase in weight of the organ.

DISCUSSION

Short-term (2-week) inhalation studies

with Fischer 344 rats and B6C3Fl mice re-

vealed a dramatic difference in the spectrum

of target organs and toxicological effects for

EGME and PGME. Exposure to vapors of

EGME resulted in pronounced treatment-

related effects on peripheral blood counts,

bone marrow, testes, and lymphoid tissues

of rats and mice, while none of these tissues

was affected in animals exposed to PGME.

The tissues which were conspicuously af-

fected by exposure to EGME vapors (bone

marrow, testicular germinal epithelium, and

thymic cortex) all have a relatively high rate

of cell division, suggesting that the test ma-

terial may inhibit mitotic processes. How-

ever, microscopic examination of the intes-

tinal epithelium and follicular cells of the

ovary, both of which also have a very high

rate of cell turnover, revealed no alterations

by the EGME exposures, thus indicating

that the observed target organ specificity of

EGME involves other factors besides cell

turnover rate.

Although of lesser toxicological signifi-

cance than the testicular and hematologic

effects, serum proteins were also reduced

following exposure to EGME vapors. Both

serum globulins and albumin were about

equally depressed following exposure to high

concentrations of EGME vapors. The

depression in serum globulins is consistent

with the microscopically observed depletion

of areas in the lymph nodes normally pop-

ulated by B-lymphocytes, possibly indicating

an impairment of the humoral immune re-

sponse. Moreover, the cellular immune re-

sponse was probably impaired as indicated

by the thymic atrophy as well as the deple-

tion of areas in the lymph nodes normally

populated by T-lymphocytes. The signifi-

cance of depression in serum albumin is un-

certain.

In sharp contrast to the pronounced treat-

ment-related changes observed in animals

exposed to EGME, remarkably little could

be attributed to exposure to a threefold

higher concentration of PGME. Central ner-

vous system depression as indicated by anes-

thesia or sedation was noted during exposure

8/17/2019 Miller 1981

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COMPARATIVE TOXICITY OF EGME AND PGME 377

of rats and mice to 3000 ppm. In addition,

rats in the 3000 ppm group had slight

changes in specific gravity of urine and slight

liver enlargement. However, there were no

associated gross or histopathologic obser-

vations in livers, kidneys, or other organs of

these animals which were related to exposure

to the test material. In general the minor

treatment-related changes in rats and mice

exposed to 3000 ppm PGME would, at most,

constitute a minimal effect. Consistent with

results obtained in earlier, longer term stud-

ies by Rowe et al. (1954) PGME had no

apparent effects on those organ systems con-

spicuously affected by EGME, i.e., bone

marrow, testes, and lymphoid tissue.

Although EGME and PGME both have

fairly high vapor pressures (9.7 and 10.9 mm

Hg at 25°C for EGME and PGME, respec-

tively) and similar solvent properties, the

present short-term inhalation studies indi-

cate a remarkable difference in the potential

hazard associated with exposure to the two

materials. Although EGME and PGME are

structurally very similar, there is a great

difference in their biological activities, clearly

illustrating the potential for error when in-

ferences about toxicity are made on the basis

of chemical structure alone.

REFERENCES

CARPENTER, C. P., POZZANI, V. C., WEIL, C. S., NAIR,

J. H., KECK, G. A., AND SMYTH, H. F. (1956). The

toxicity of butyl cellosolve solvent. Arch. Ind. Health.

14, 114-131.

DONLEY, D. E. (1936). Toxic encephalopathy and vol-

atile solvents in industry. J. Ind. Hyg. T oxico l. 18,

511-577.

GOLDBERG, M. E., JOHNSON, H. E., POZZANI, V. C.,

AND SMYTH, H. F., JR. (1964). Ef fec t of repeated

inhalation of vapors of industrial solvents on animal

behavior. I. Evaluation of nine solvent vapors on pole-

climb performance in rats. Amer. Znd. Hyg. Asso c.

J. 25,369-375.

GREENBURG, L., MAYERS, M. R., GOLDWATER, L. J.,

BURKE, W. J. , AND MOSCOWITZ, S. (1938). Health

hazards in the manufacture of “fused collars”. I. Ex-

posure to ethylene glycol monomethyl ether. J. Ind.

Hyg. Toxico l. 20, 134- 147.

MILLER, R. R., LEGS, R. L., POTTS, W. J. , AND

MCKENNA, M. J. (1980). Improved methodology for

generating controlled test atmospheres. Amer. Znd.

Hyg. Assoc. J. 41, 844-846.

NAGANO, K., NAKAYAMA, E., KOYANO, M., DOBAY-

ASKI, H., ADACHI, H., AND YAMADA, T. (1979).

Testicular atrophy of mice induced by ethylene glycol

monoalkyl ethers.

Japan J. Znd. Health

21, 29-35.

OHI, G., AND WEGMAN, D. H. (1978). Transcutaneous

ethylene glycol monomethyl ether poisoning in the

work setting. J. Occup. Med. 20, 675-676.

PARSONS, C. E., AND PARSONS, M. E. (1938). Toxic

encephalopathy and “granulopenic anemia” due to

volatile solvents in industry: Report o f two cases. J.

Ind. Hyg. Toxico l. 20, 125- 133.

ROWE, V. K., MCCOLLISTER, D. D., SPENCER, H. C.,

OYEN, F., HOLLINGSWORTH, R. L., AND DRILL,

V. A. (1954). Toxicology of mono-, di, and tri-pro-

pylene glycol methyl ethers. A.M.A. Arch. Ind. Hyg.

Occup. Med. 9, 509-525.

SCHALM, 0. W. (1965). Veterinary Hematology. Lea

& Febiger, Philadelphia, Pennsylvania.

WERNER, H. W., MITCHELL, J. L., MILLER, J. W., AND

VON OETTINGEN, W. F. (1943a). The acute toxicity

of several monoalkyl ethers of ethylene glycol. J. Ind.

Hyg. Toxico l. 25, 151-162.

WERNER, H. W., NAWROCKI, C. Z., MITCHELL, J. L.,

AND VON OE-ITINGEN, W. F. (1943b). Ef fec ts of re-

peated exposure of rats to vapors of monoalkyl eth-

ylene glycol ethers. J. Ind. Hyg. Toxic ol. 25, 374-

319.

WERNER, H. W., MITCHELL, J. L., MILLER, J. W., AND

VON OE~INGEN, W. F. ( 1943~). E ffects of repeated

exposure of dogs to monoalkyl ethylene glycol ether

vapors. J. Ind. Hyg. Toxico l. 25, 409-414.

WILEY, F. J., HEUPER, W. C., BERGEN, D. S., AND

BLOOD, F. R. (1938). The formation of oxalic acid

from ethylene glycol and related solvents. J. Ind. Hyg.

Toxico l. 20, 269-217.

ZAVON, M. R. (1963). Methyl cellosolve intoxication.

Amer. Ind. Hyg. Ass oc. J. 24, 36-41.