TOXICOLOGY AND APPLIED PHARMACOLOGY 77, 187-200 (1985) 

Acute Toxicity and Recovery in the Hemopoietic System of Rats after 

Treatment with Ethylene Glycol Monomethyl and Monobutyl Ethers 

DEREK GRANT, SUE SUESH, Huw B. JONES, SHARAT D. GANGOLLI, 

AND WILLIAM H. BUTLER 

The British Industrial Biological Research Association, Woodmansteme Road, 

Carshalton. Surrey, SM5 4DS, England 

Received May 10, 1984; accepted August 27, 1984 

Acute Toxicity and Recovery in the Hemopoietic System of Rats after Treatment with 

Ethylene Glycol Monomethyl and Monobutyl Ethers. GRANT, D., SULSH, S., JONES, H. B., 

GANGOLLI, S. D., AND BUTLER, W. H. (1985). Toxicol. Appl. Pharmacol. 77, 187-200. Male 

rats were given ethylene glycol monomethyl ether (EGM) or ethylene glycol monobutyl ether 

(EGB) po for 4 consecutive days at doses of 100 or 500 mg/kg body wt/day for EGM, and 500 

or 1000 mg/kg body wt/day for EGB. Animals were killed on Days 1,4, 8, and 22 atIer the 

final treatment. Both EGM and EGB produced thymic atrophy and lymphocytopenia and, in 

the cam of EGM, neutropenia also. Hemolytic anemia induced by EGB resulted in splenic 

extramedullary hemopoicsis, hypcrplasia of both spleen and bone marrow, and rcticulocytosis. 

Apart from residual slight increases in spleen weight, mean red cell volume, and mean 

corpuscular hemoglobin at the end of the recovery period, other effects were reversible. With 

EGM, reduction in the numbers of circulating red cells was only slight. Treatment with EGM 

also abolished splenic extramedtdkuy hemopoiesis which pamally recovered on Day 4, followed 

by a marked response on Day 8, and return to the moderate control values on Day 22. Femoral 

bone marrow was hemorrhagic 1 day after treatment with EGM which appeared to be 

associated with sinus endothelial cell damage. By Day 4 the histologic appearance of the 

marrow was normal. Testicular atrophy was also produced in EGM-treated animals which 

persisted for the duration of the experiment. It is concluded that EGM and EGB differ 

considerably in the spectrum of toxic changes induced, and apart from testicular atrophy, these 

changes were. largely reversible within a short time of the end of treatment. 8 1985 Academic 

Pras. Inc. 

Ethylene glycol monoalkyl ethers are colorless 

volatile liquids with widespread industrial 

applications owing to their miscibility with 

many organic solvents, and with water- and 

oil-based formulations. The presence of ethylene glycol ethers in paints, lacquers, dyes, 

inks, and cleaning agents has generated considerable interest in their toxicology. Several 

case histories have been reported in which 

adverse effects were produced in individuals 

who had absorbed ethylene glycol ethers 

through the skin by direct contact (Ohi and 

Wegmann, 1978), via the lung after inhaling 

vapors (Avon, 1963), or through the gut 

when mistaken for alcohol and ingested (Nitter-Hauge, 1970). 

The spectrum of toxicity induced by the 

ethylene glycol ethers in various species include disorders of the hemopoietic, reproductive, and central nervous systems, with 

the site of action and severity of toxicity 

depending upon the particular ethylene glycol 

ether and species involved (ECETOC, 1982). 

In view of the reported differences in toxicity between closely related ethylene glycol 

ethers (Werner et al., 1943; Carpenter et al., 

187 0041-008X/85 $3.00 

Cowi@ 8 1985 by Academic Press, Inc. 

All rights of npmduction in any form -4. 
188 GRANT 

1956; Nagano et al., 1979), a comparative 

study was initiated using ethylene glycol 

monomethyl ether (EGM) and ethylene glycol 

monobutyl ether (EGB) to characterize the 

differences in toxicity in the hemopoietic 

system and the reversibility of such effects in 

the period following treatment. 

METHODS 

Animals. Male F344 rats, aged approximately 4 weeks, 

were obtained from Charles River U.K. Ltd., Margate, 

Kent. They were housed in a room designed to provide 

a temperature of 20 + 2°C 12 to 15 air changes per 

hour, a relative humidity of 40 to 602, and a lighting 

cycle of 12 hr light: 12 hr dark. Animals were allowed 

free access to feed (R & M No. 1 expanded, Special Diet 

Services, Witham, Essex) and domestic mains water 

throughout. 

Materials. EGM was obtained from Sigma Chemical 

Company, Poole, Dorset, and EGB from Aldrich Chemical Company, Gillingham, Dorset. The purity of both 

test materials was 99.9% as determined by gas-liquid 

chromatography. 

Design and treatment. On receipt, rats were randomly 

assigned to five groups with the aid of random number 

tables (Fisher, 1965). Each group contained 24 animals, 

housed 6 to a cage and allowed to acclimatize for 1 

week. Animals were dosed po with water (control), EGM 

(100 or 500 m&kg/day), or EGB (500 or 1000 mg/kg/ 

day) daily for 4 consecutive days. The glycol ethers were 

diluted in water and given at a dose volume of 5 ml/kg 

body wt. These doses of EGM and EGB were chosen on 

the basis of effects obtained in preliminary range finding 

studies. Six animals from each group were bled, then 

killed, and autopsied on Days 1, 4, 8, and 22 after the 

last treatment. 

Hematology. Animals were warmed in a container 

heated to approximately 40°C and bled from a lateral 

caudal vein, and the following were determined: red 

blood cell count (RBC), white blood cell count (WBC), 

hemoglobin concentration (Hb), mean red cell volume 

(MCV), hematocrit (Hct), reticulocyte count, and differential white cell count. The RBC, WBC, Hct, and MCV 

were determined on a Coulter Counter (model ZF) 

coupled to a Coulter MCV/Hct accessory. During the 

period of reticulocytosis in EGB-treated animals, the 

WBC was determined by a manual method using an 

improved Neubauer counting chamber. Hemoglobin 

concentrations were measured on a Coulter Hemoglobinometer. 

Necropsy and histopathology. After overnight fasting, 

animals were weighed and killed by ip injection with 

sodium pentobarbitone. The spleen, thymus, liver, testes, 

and kidneys were weighed, and together with cervical 

ET AL. 

and mesenteric lymph nodes, these were fixed in neutral 

buffered Formalin for examination by light microscopy. 

Femoral bone marrow was immersed in a solution 

containing 4% formaldehyde and 1% glutaraldehyde 

adjusted to pH 7.2 with 0.1 M phosphate buffer (McDowell and Trump, 1976), a fixation method suitable 

for both light and electron microscopy. Samples of 

marrow for electron microscopy were postfixed in 1% 

osmium tetroxide, dehydrated through graded ethanols, 

and embedded in agar lOO/araldite. Sections were cut at 

a thickness of 1 pm and stained with toluidine blue for 

light microscopy, or at a thickness of 60 to 90 nm and 

stained with lead citrate and uranyl acetate for transmission electron microscopy. Other samples of bone marrow 

and the remainder of the tissues were processed into 

paraffin wax, cut at 5 pm, and stained with hematoxylin 

and eosin. 

Statistical analyses. Data were analyzed by one-way 

analysis of variance; means were compared by least 

significant difference criteria (Snedecor and Cochran, 

1968). 

RESULTS 

Body Weights and Organ Weights 

The mean weights of the animals were 

similar in all groups before the commencement of treatment. Treatment-related reductions in the rates of body weight gain were 

seen only in the high-dose EGB group (Table 1). 

Reduced relative weights (g/ 100 g body wt) 

of kidneys, spleen, testes, and thymus were 

seen in EGM-treated rats on Day 1 of recovery (Table 1). With the exception of weights 

of kidneys, these reductions were dose related. 

The weights of spleens recovered to exceed 

control values by Day 8. By Day 22, all 

organ weights in EGM-treated animals were 

similar to or slightly higher than those of the 

control group apart from weights of testes 

which remained lower throughout. 

In contrast, EGB caused dose-related increases in the relative weights of spleen, liver, 

and kidneys on Day 1 of recovery, but in 

common with EGM, thymic weights were 

reduced (Table 1). These weight changes in 

EGB-treated animals returned to normal by 

Day 22 apart from the weights of livers and 

spleens which remained slightly raised. 
ACUTE TOXICITY OF GLYCOL ETHERS 189 

TABLE 1 

RELATIVE ORGAN WEIGHTS OF MALE F344 RATS DOSED WITH ETHYLENE GLYCOL MONOMETHYL ETHER 

(EGM) OR ETHYLENE GLYCOL MONOBUTYL ETHER (EGB) 

Dose 

bWkg/day) 

Body wt 

(9) Liver 

Relative organ weight (g/lOOg body w-t) 

Spleen Kidneys Testes Thymus 

CON 

EGM 

EGB 

CON 

EGM 

EGB 

CON 

EGM 

EGB 

CON 

EGM 

EGB 

0 

100 

500 

500 

1000 

0 

100 

500 

500 

1000 

0 

100 

500 

500 

1000 

0 

100 

500 

500 

1000 

62.0 

(2.6) 

68.S 

(5.2) 

64.5 

(3.8) 

64.0 

(5.6) 

53.722 

(5.3) 

16.2 

(7.4) 

14.2 

(8.1) 

72.7 

(4.9) 

(81.5) 

(7.4) 

56.4*** 

(7.5) 

92.0 

(6.4) 

105.5* 

(9.0) 

84.5 

(14.6) 

102.5 

(10.1) 

71.5’ 

(11.1) 

113.2 

(5.8) 

171.8 

(7.1) 

141.8*** 

(15.0) 

162.0 

(10.3) 

147.5** 

(17.8) 

Day 1 recovery 

3.869 0.326 

(0.157) (0.010) 

3.628 0.305 

(0.216) (0.0 18) 

3.67 1 0.237*** 

(0.182) (0.028) 

4.480*** 0.610*** 

(0.113) (0.079) 

4.921**’ 0.669*** 

(0.314) (0.030) 

Day 4 recovery 

3.620 0.337 

(0.040) (0.032) 

3.542 0.306 

(0.165) (0.026) 

3.490 0.296 

(0.137) (0.028) 

4.001** 0.435*** 

(0.165) (0.018) 

4.381*** 0.532*** 

(0.438) (0.055) 

Day 8 recovery 

3.789 0.335 

(0.115) (0.022) 

3.766 0.354 

(0.112) (0.011) 

3.653 0.431*** 

(0.161) (0.0 14) 

4.019* 0.394** 

(0.094) (0.018) 

4.244+++ 0.436*** 

(0.277) (0.056) 

Day 22 recovery 

3.312 0.284 

(0.148) (0.021) 

3.355 0.211 

(0.094) (0.030) 

3.446 0.330* 

(0.191) (0.04 1) 

3.315 0.307 

(0.112) (0.028) 

3.550* 0.338** 

(0.171) (0.025) 

I .06 1.051 

(0.030) (0.199) 

0.969++ 1.016 

(0.040) (0.156) 

0.997* 0.630** 

(0.033) (0.100) 

1.036 0.954 

(0.041) (0.225) 

1.191*** 0.891 

(0.080) (0.338) 

0.913 

(0.035) 

0.926 

(0.031) 

0.903 

(0.03 1) 

0.946 

(0.054) 

1.085*** 

(0.059) 

1.080 

(0.098) 

0.946 

(0.286) 

0.624*** 

(0.101) 

1.152 

(0.169) 

1.174 

(0.126) 

0.885 

(0.018) 

0.863 

(0.06 1) 

0.908 

(0.029) 

0.916 

(0.042) 

1 .OOO* 

(0.113) 

1.123 

(0.323) 

0.909 

(0.314) 

0.633** 

(0.034) 

1.280 

(0.05 1) 

1.234 

(0.334) 

0.719 

(0.028) 

0.726 

(0.033) 

0.787** 

(0.040) 

0.720 

(0.030) 

0.703 

(0.192) 

1.332 

(0.059) 

1.356 

(0.054) 

0.615*** 

(0.079) 

1.377 

(0.055) 

1.261 

(0.268) 

0.262 

(0.040) 

0.214* 

(0.024) 

0.096*** 

(0.030) 

0.261 

(0.032) 

0.164*** 

(0.036) 

0.309 

(0.012) 

0.251* 

(0.030) 

0.115*** 

(0.024) 

0.294 

(0.023) 

0.187*** 

(0.09 1) 

0.298 

(0.02 1) 

0.258* 

(0.025) 

0.117*** 

(0.014) 

0.275 

(0.047) 

0.2 13*** 

(0.039) 

0.205 

(0.022) 

0.198 

(0.022) 

0.238 

(0.043) 

0.210 

(0.0 17) 

0.219 

(0.039) 

Note. Values are the means of six animals and those marked with an asterisk differ significantly from the control 

values using least significant difference criteria (*p < 0.05, **p < 0.01, ***p < 0.001). Figures in parentheses 

are SD. 

ACUTE TOXICITY OF GLYCOL ETHERS 191 

Histopathology 

In the high-dose EGM group, femoral 

bone marrow was severely hemorrhagic, with 

loss of much of the normal nucleated tissue 

(Fig. 1). Electron microscopy revealed extensive thinning of the sinus endothelial cells of 

marrow sinuses which had cytoplasmic processes extending into ‘the lumen (Fig. 2). 

Large discontinuities which often contained 

erythrocytes were frequently seen in the endothelial cell layer in the sinuses. These 

breaks were not at the point of cell to cell 

contact as the zonulae adherens were intact. 

Pinocytotic activity was normal as judged by 

the numbers and appearance of vesicles, although some cells contained a small number 

of autophagosomes and secondary lysosomes. 

There was also slightly increased electron 

density and crenation of some nuclei. Despite 

the severity of the initial hemorrhage, the 

normal architecture of the marrow was restored by Day 4. Only one of the six animals 

in the low-dose group had hemorrhagic marrow on Day 1. 

In the spleen the moderate amount of 

extramedulhuy hemopoiesis (EMH) normally 

present in animals of this age was abolished 

by treatment with 500 mg EGM/kg body wt, 

and reduced in most of the lOO-mg EGM/ 

kg body wt group (Fig. 3). This reduced 

amount of EMH returned to normal or near 

normal values in the lowdose EGM group 

within 8 days, whereas in animals of the 

high-dose group there was partial recovery 

on Day 4 and a marked increase on Day 8. 

The degree of EMH had returned to normal 

by Day 22. 

Testicular atrophy was severe in the highdose EGM group with disruption of the 

architecture of the seminiferous tubules and 

degenerative changes in the spermatocytes 

similar to those described by Greasy and 

Foster (1984). This change was reflected in 

the absence of spermatozoa in the epididymides. Testes were of normal histologic appearance in the low-dose EGM group. 

Treatment with EGB produced marrow 

hyperplasia with no evidence of hemorrhage 

at any time. Splenic EMH was marked in 

both EGB-treated groups on Day 1 but this 

change had returned to normal by Day 8. 

Unlike EGM, treatment with EGB had no 

discemable effects on the testes. 

Histologic changes common to rats treated 

with either EGM or EGB at the high doses 

were slight hepatic EMH in the first week of 

recovery and lymphocyte depletion of the 

thymic cortex on Day 1 (Erg. 4). This lymphocyte depletion was only transient as the 

appearance of thymic tissue was normal by 

Day 4. Kidneys and lymph nodes were of 

normal appearance in all groups. 

Hematology 

Changes in the circulating blood were produced by both EGM and EGB, but there 

were qualitative and quantitative differences 

in the responses seen. 

EGM (Table 2) produced slight reductions 

of the BBC, Hct, and Hb values at Day 4 

and 8 posttreatment, resulting in a mild 

normochromic, normocytic anemia. The reticulocyte count was slightly depressed in 

these EGM-treated. animals on Days 1 and 

4, whereas on Day 8 the numbers of circulating reticulocytes were signScantly increased (p < 0.05). 

The leukocyte count was markedly reduced 

in the high-dose EGM group on Day 1 due 

to reduced numbers of neutrophils and lymFIG. 1. Femoral bone marrow morphology-Day 1 recovery. (a) Control rat. Note the well-ordered 

nucleated marrow tissue surrounding a sinus. (b) Rat treated with 500 mg EGM/k&Iay for 4 consecutive 

days. The sinus endothelium is morphologically abnormal with an irregular outline and large gaps in 

which red blood cells can be seen. Much of the normal nucleated marrow tissue is missing, and there are 

large numbers of mature red cells occupying the extravascular areas. Resin embedded, I-srn sections, 

stained with toluidine blue stain, X1460. 
192 GRANT ET AL. 

FIG, 2. Sinus endothelial cell ultrastructure-Day 1 recovery. (a) Control rat. The nuclei and luminal 

surfaces of the endothelium are smooth in outline. (b) Rat treated with 500 mg EGM/kg/day for 4 

consecutive days. The endothelial cell nuclei are very irregular in outline and the cytoplasm varies from 

extreme thinness to areas of thickening with frequent knob-like processes. Lead citrate and uranyl acetate 

staining, x2030. Inset shows irregular endothelium with intact zonulae adherens, x7190. 

phocytes. These leukocyte counts subse- Animals treated with the lower dose of EGM 

quently increased but failed to reach control had slightly reduced leukocyte counts on 

values by the end of the recovery period. Day 1. 
ACUTE TOXICITY OF GLYCOL ETHERS 193 

In contrast, EGB (Table 2) caused pronounced dose-dependent effects on circulating 

red and white cells. Animals treated with the 

highest dose of EGB (1000 mg/kg body wt/ 

day) had reduced RBC, Hct, Hb, and markedly elevated MCV, reticulocyte counts, and 

mean corpuscular hemoglobin (MCH) at the 

end of treatment. Most of these changes in 

the red cells disappeared over the recovery 

period, although the MCV and MCH remained slightly elevated at Day 22. The 

reticulocytosis was particularly striking on 

Days 1 and 4, but by Day 8 the reticulocyte 

counts had returned to normal. Examination 

of Romanowski-stained blood films taken 

from this group revealed increased numbers 

of circulating nucleated RBCs (normoblasts), 

pronounced anisocytosis, polychromasia, and 

the presence of Howell Jolly bodies (Fig. 5). 

These changes had resolved by Day 8. Leukocyte counts were also depressed on Day 1 

in the high-dose EGB group, due principally 

to a reduction in the numbers of circulating 

lymphocytes. The leukocyte numbers gradually increased, although, in common with 

EGM-treated animals, they did not reach 

control values by the end of the recovery 

period. These effects on red and white cells 

were also seen in animals treated with the 

lower dose of EGB (500 mg/kg body w-t/ 

day), although the severity of the changes 

was less marked. 

DISCUSSION 

The two ethylene glycol ethers, EGM and 

EGB, which differ only in their alkyl moieties, 

produced several markedly dissimilar changes 

in circulating blood and selected tissues after 

acute treatment. 

The major hematological effect of EGM 

was leukopenia, whereas EGB produced both 

leukopenia and anemia. The pronounced 

leukopenia in EGM-treated animals appeared 

to be associated with reductions in both 

lymphocytes and neutrophils, as opposed to 

those treated with EGB in which lymphocytes 

were preferentially affected. With both ethylene glycol ethers there was also a loss of 

lymphocytes from the thymic cortex and 

reductions in thymic weights, but whether 

this change indicates direct toxicity to the 

thymus or is mediated by possible effects on 

circulating lymphocytes or bone marrow is 

unclear. 

Since lymphocytopenia was common to 

animals treated with either of the ethylene 

gIyco1 ethers, but marrow toxicity was confined to those treated with EGM, the lymphocytopenia does not appear to be related 

to bone marrow toxicity. There does, however, seem to be some association between 

neutropenia and bone marrow toxicity in 

EGM-treated animals. The impairment of 

granulopoiesis in damaged marrow would be 

expected to lead to a rapid neutropenia owing 

to the short half-life of neutrophils in the 

circulating blood (Wade and Mandell, 1983). 

Full recovery from the leukopenia produced by the ethylene glycol ethers was 

equivocal owing to the raised number of 

circulating leukocytes in control animals at 

the end of the recovery period. 

The reductions in RBC, Hct, Hb, and 

marginally lower reticulocyte counts during 

the initial period of recovery from EGM 

treatment, together with reduced splenic 

EMH and bone marrow toxicity, suggest an 

inhibitory action on erythropoiesis. If continued this inhibition would eventually lead to 

anemia by the failure to replace effete red 

cells. Indeed, it has been reported that anemia 

occurs in rats and several other species when 

the duration of exposure to EGM is more 

prolonged (Miller et al., 1981; Doe et al., 

1983). On Day 8 the markedly elevated 

splenic EMH and the modest increase in the 

numbers of circulating reticulocytes suggest 

recovery from the inhibition of erythropoiesis. 

In contrast, the various changes seen in 

circulating red cells after EGB treatment are 

typical of hemolytic anemia with an associated reticulocytosis and hyperplasia of both 

bone marrow and spleen. This observation 

is in agreement with the findings of Carpenter 
194 GRANT ET AL. 
ACUTE TOXICITY OF GLYCOL ETHERS 195 

FIG. 3. Splenic extramedullary hemopoiesis (EMH)-Day 1 recovery. (a) Control rat. Islands of EMH 

are clearly distinguishable in the red pulp area. (b) Rat treated with 500 mg EGM/kg/day for 4 consecutive 

days. The red pulp is devoid of any overt EMH. (c) Rat treated with 1000 mg EGB/kg for 4 consecutive 

days. Note the marked increase in EMH which occupies a major proportion of the red pulp, H & E, 

X290. 

et al. (1956) who have demonstrated hemolysis and increased osmotic fragility in rats 

treated with EGB. 

The majority of these effects on the red 

cell population were reversible, although increases in MCH and MCV were more per& 

tent, probably due to the selective hemolytic 

action of EGB on aged red cells (Carpenter 

et al., 1956), leaving a population of young 

erythrocytes. In addition, erythrocytes which 

are produced during remission from severe 

acute anemia tend to be macro&c and 

contain more Hb (Schalm et al., 1975), factors 

which may also contribute to the persistence 

of these changes. The long-lasting spleen 

weight increases produced by these ethylene 

glycol ethers may be a residual effect of the 

elevated concentration of splenic EMH. 

In contrast to the proliferative response in 

the marrow of EGB-treated animals, those 

given EGM had severely hemorrhagic marrows. The major site of toxicity relating to 

hemorrhage appeared to be endothelial cells 

lining the sinuses, many of which had evidence of damage. The presence of mature 

erythrocytes in the large gaps of the sinus 

walls and their abundance in the substance 

of the marrow tissue suggest that the integrity 

of the sinus endothelium was impaired. This, 

together with the loss of the resident population of nucleated cells, agrees with previous 

reports of marrow hypocellularity after treatment with EGM (Miller et al., 1981). The 

pathogenesis of nucleated marrow cell loss is 

unclear at present. 

Testicular atrophy similar to that described 

by Foster et al. (1983) and Creasy and Foster 

( 1984) was evident in animals treated with 
TABLE 2 

HEMATOL~CY OF MALE F344 RATS DOSED WITH ETHYLENE GLYCOL MONOMETHYL ETHER (EGM) OR ETHYLENE GLYCOL 

Dose RBC 

b%.Wday) ( lo’2/1) 

MCV 

(fl) Hct (%) 

Hb 

(g/d]) 

Reticulocytes 

(IRBC) 

MCH 

(PP) Total 

CON 

EGM 

EGB 

CON 

EGM 

EGB 

0 

100 

500 

500 

loo0 

0 

100 

500 

500 

1000 

6.55 60.2 38.7 

(0.15) (1.2) (1.5) 

6.58 59.7 38.8 

(0.28) (0.5) (1.3) 

6.67 59.3 39.2 

(0.2 1) W-V (1.3) 

5.04*** 74.5*** 37.3 

(0.50) (2.2) (2.7) 

3.34*** 82.7*** 27.8*** 

(0.6 I) (2.5) (4.3) 

6.65 59.2 

(0.3 1) 03.8) 

6.64 57.7 

(0.47) W3) 

6.22 57.5 

(0.17) (0.6) 

6.06* 68.7*** 

(0.28) (2.9) 

4 80*** ” 

(0:72) 

77 6*- ’ 

(4:2) 

38.7 

(1.5) 

37.7 

(2.7) 

35.3* 

(1.4) 

41.2 

(1.2) 

37.2” 

(4.4) 

Day 1 recovery 

15.7 4.2h 

(0.3) (1.8) 

15.7 3.9 

(0.6) W) 

15.4 2.7 

(0.4) (1.0) 

14.0* 25.2*** 

(1.1) (9.3) 

10.6*** 32.6**+ 

(1.9) (6.9) 

Day 4 recovery 

16.3 10.4 

(0.5) (3.6) 

15.9 9.1 

(0.6) (5.1) 

14.4*** 6.6” 

(0.4) (5.9) 

16.7 22.4+ 

(0.5) (9.9) 

15.3*” 51 3*** U 

(1.2) (11:8) 

24.0 4.93 

(0.4) 

(1.19) 

23.8 3.85; 

(0.5) (0.31) 

23.1 1.52-f 

(0.5) (0.32) 

27.9*** 2.68*** 

(1.0) (0.61) 

3 I .8*** 1.75-e 

(1.6) (0.39) 

24.5 5.23 

(0.6) 

(0.52) 

24.0 6.04** 

(1.4) (0.60) 

23.2 3.00*** 

(0.5) 

(0.31) 

27.6** 4.59* 

(1.8) (0.48) 

32.1*** ” 2 36*** a 

(0140) 

(2.3) 
CON 

EGM 

EGB 

CON 

EGM 

EGB 

0 

100 

500 

500 

1000 

0 

100 

500 

500 

1000 

6.94 

(0.29) 

6.99 

(0.28) 

6.46. 

(0.25) 

6.23*** 

(0.30) 

6.16*** 

(0.39) 

7.63 

(0.25) 

7.72 

(0.12) 

7.39 

(0.70) 

7.46 

(0.2 1) 

7.36 

(0.15) 

60.5 41.5 

(0.6) (2.1) 

59.2 41.0 

(1.2) (2.2) 

60.5 38.5* 

(1.1) (2.1) 

65.2*** 40.3 

(1.2) (2.4) 

71 o***” 

(3:2) 

42.8” 

(2.3) 

58.7 43.8 

(1.4) (2.1) 

57.3f 43.5 

(0.5) (0.6) 

58.7 42.7 

(0.8) (5.0) 

59.0 43.4 

(0.9) (1.6) 

6 1.2*** 44.5 

(0.8) (0.6) 

Day 8 recovery 

16.7 5.5 

(0.7) (1.9) 

16.1 

(0.3) (3) 

15.5** 

(0.8) 

,;:;; 

16.5 

(0.7) 

(K) 

17.4 6.9 

(0.7) (2.6) 

Day 22 recovery 

16.7 3.2 

(0.5) (1.1) 

16.5 3.8 

(0.2) (1.3) 

16.9 3.2 

(1.3) (1.0) 

17.2 

(0.4) 

,::,“, 

17.3 

(0.2) 

(2) 

24.0 6.13 

(0.5) 

(1.08) 

23.1 5.39 

(0.8) 

(0.85) 

23.9 4.49- 

(0.6) 

(0.58) 

26.5*** 5.52 

(0.9) 

(0.47) 

29.4*** 5.55” 

(1.2) (0.82) 

21.9 9.90 

(0.3) 

(2.97) 

21.3’ 8.43 

(0.2) (3.97) 

22.9 6.25*+ 

(0.7) 

(0.8 1) 

23.0*** 6.06** 

(0.3) 

(0.41) 

23.5*** 5.30** 

(0.5) (0.42) 

Note. Values are the means of six animals and those marked with an asterisk differ significantly from the control values using 

4 0.05, **p < 0.01, l **p -C 0.001). Figures in parentheses are SD. 

” Mean value of five animals. 

h Mean value of four animals. 

’ Mean value of three animals. 
FIG. 4. Thymus morphology-Day I recovery. (a) Control rat. Note the clear distinction between the 

outer cortex and inner medulla. (b) Rat treated with 500 mg EGM/kgjday for 4 consecutive days. There 

is considerable depletion of lymphocytes from the cortex and an increased lymphocyte population in the 

medulla. The demarcation between the two areas is less distinct, H & E, X60. 

198 
ACUTE TOXICITY OF GLYCOL ETHERS 199 

FIG. 5. Blood film from a rat given 1000 mg EGB/kg/day for 4 consecutive days-Day I recovery. 

Note the pronounced polychromasia, anisocytosis, and nucleated red blood cell (normoblast) containing 

a Howell Jolly body. May-Grunwald-Giemsa stain, X 1460. 

500 mg EGM/kg body wt. This atrophy 

persisted for the duration of the recovery 

period, whereas EGB had no discemable 

effect on either testis weights or on their 

histologic appearance at doses which were 

clearly toxic to the hemopoietic system. The 

studies by Foster et al. (1983) have shown 

that a longer period of recovery, equivalent 

to one maturation cycle (7 to 8 weeks), after 

dosing rats with 500 mg EGM/kg body wt 

permits the resumption of spermatogenesis. 

In conclusion, it is clear that there are 

considerable differences between EGM and 

EGB in many of the toxic changes induced, 

and that, apart from testicular atrophy, most 

of the other histologic and hematologic 

changes resolve within 3 weeks or less of the 

cessation of treatment. The reasons for the 

differential toxicity between the two glycol 

ethers are unknown, but it is likely that 

events related to the metabolism of the two 

compounds are involved as the acetic acid 

metabolites appear to be largely responsible 

for the toxic effects induced by the ethylene 

glycol ethers (Miller et al., 1982, 1983). 

ACKNOWLEDGMENTS 

We thank Mrs. L. Beech for the preparation of specimens for electron microscopy, and Mr. A. Dagnall for 

photographic assistance. This work is part of a research 

program on acute/chronic toxicity relationships, and we 

thank the Food and Drink Industries Council for their 

support. 

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