2-ethoxyethanol

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Very detailed documentation about methodology and results. No information if GLP compliant. No CAS Nr. or batch number or product but name of substance and purity stated.

Data source

Reference

Reference Type:

publication

Title:

Subchronic Inhalation Toxicology of Ethylene Glycol Monoethyl Ether in the Rat and Rabbit

Author:

Barbee S.J., Terrill J.B., DeSousa D.J., Conaway C.C.

Year:

1984

Bibliographic source:

Environ. Health Perspect. 57, 157-163

Materials and methods

Principles of method if other than guideline:

Subchronic (13 week) inhalation toxicity

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

2-ethoxyethanol

EC Number:

203-804-1

EC Name:

2-ethoxyethanol

Cas Number:

110-80-5

Molecular formula:

C4H10O2

IUPAC Name:

2-ethoxyethan-1-ol

Details on test material:

Test substance as stated in publication: ethylene glycol monoethyl ether; abbreviation: EGEE
Purity: 99.59 %
Supplier: Eastman Chemical Products, Inc. (Kingsport, TN)

Test animals

Species:

other: rat, rabbit

Strain:

other: Sprague-Dawley CD (rat), New Zealand White (rabbit)

Sex:

male/female

Details on test animals or test system and environmental conditions:

Rats:
Supplier: Charles River Breeding Laboratories (Wilmington, MA)
Number of animals: 120
Weight: 149 to 275 g
Acclimatisation: 15 d
Feed type: Purina Rodent Laboratory Chow No. 5001

Rabbits:
Supplier: Dutchland Laboratories, Inc. (Denver, PA)
Number of animals: 80
Weight: 2.1-3.3 kg
Acclimatisation: 22 d
Feed type: Purina Rabbit Laboratory Chow HF No. 5326
---
Housing and keeping conditions the same for rat and rabbit:
during non-exposure stainless steel wire mesh cages, kept individually, temperature controlled, humidity controlled, light/dark cycle 12 h/12 h, feed and water ad libitum
---
Exposure: All animals were exposed in 10 m3 stainless steel and glass chambers. During exposure they were housed individually in stainless steel wire mesh cages. (provided information in publication)

Administration / exposure

Route of administration:

inhalation: vapour

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

6 hours/day, 5 days/week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 25, 100 and 400 ppm (equals 0, 92.5, 390 and 1480 mg/m3)
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 25 +/- 1, 103 +/- 6, 403 +/- 10 ppm (rats)
Basis:
analytical conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 25 +/- 1, 103 +/- 6, 403 +/- 10 ppm (rabbits)
Basis:
analytical conc.

Doses / concentrations 4

Remarks:

Doses / Concentrations:
Deviation from +/- 10 % of the target concentration: one day at 19 ppm at lowest nominal concentration
Basis:
analytical conc.

No. of animals per sex per dose:

per dose group: 15 female + 15 male (rats); 10 female + 10 male (rabbits)

Control animals:

other: yes, concurrent exposure to air, same keeping conditions as other treatment groups

Details on study design:

rat study: 3 treatment groups, 1 control group; rabbit study: 3 treatment groups, 1 control group
Post-exposure period (rat and rabbit study): no

Examinations

Statistics:

The data were analysed statistically by using tests including Bartlett's test, ANOVA, Dunnett's test, Kruskal-Wallis test, summed rank test (Dunn), regression analysis, and Jonckheere's statistic test.

Results and discussion

Effect levels

1

Dose descriptor:

NOEL

Effect level:

>= 97 - <= 109 ppm (analytical)

Sex:

male/female

Basis for effect level:

other: mean analytical concentration 103 ppm; nominal concentration 390 mg/m³ (= 100 ppm); rabbit study

2

Dose descriptor:

NOEL

Effect level:

>= 393 - <= 413 ppm (analytical)

Sex:

male/female

Basis for effect level:

other: mean analytical concentration 403 ppm; nominal concentration 1480 mg/m³ (= 400 ppm); rat study

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Results:

An increased incidence of lacrimation and mucoid nasal discharge was observed in all treated groups relative to controls from week 2 through week 10. However, these observations did not occur in a dose-related pattern. The ophthalmoscopic examination revealed

no treatment-related effects.

The growth of both male and female rabbits was depressed slightly compared to controls (body weight gain) although a clear dose

response was evident only at 400 ppm. The body weight data for the treated rats were not different significantly from control values. The incidence of organ weight changes in treated relative to control animals was low in both species (Table 2). The adrenal weight from male rabbits was decreased in those animals exposed to 25 ppm EGEE. No change was noted at higher concentrations.

The testes weight was decreased significantly in this species at 400 ppm. The relative brain weight of each animal (grams of organ per 100 g of body weight) was increased at an concentrations in female rabbits, but this was due to decreases from controls in terminal body weights. In rats, the only organ weight changes consisted of a decrease in absolute and relative pituitary weight in males exposed to 400 ppm and a decrease in absolute spleen weight at an concentrations in females. The decrease in relative spleen weight was significant only at the low and high concentrations.

Terminal body weights and organ weights of rabbits and rats exposed subchronically to 2 -ethoxyethanol vapour:

			Organ and organ weights
Species	Sex	Exposure concentration [ppm]	Body [g]	Adrenals [mg]	Testes [g]	Brain [g]	Pituitary [g]	Spleen [g]
Rabbit	M	0	3700 +/- 300	424 +/- 86	8.19 +/- 0.82	9.50 +/- 0.57
		25	3500 +/- 200	304 +/-78	8.73 +/- 1.19	9.50 +/- 0.42
		100	3600 +/- 200	364 +/- 86	8.73 +/-0.69	9.71 +/- 0.35
		400	3400 +/- 200	351 +/- 89	6.36 +/- 0.99	9.29 +/- 0.39
Rabbit	F	0	3700 +/- 300	324 +/- 79		9.20 +/- 0.55
		25	3300 +/- 400	318 +/- 30		9.42 +/- 0.37
		100	3500 +/- 300	289 +/- 54		9.20 +/- 0.48
		400	3300 +/- 300	282 +/- 60		9.33 +/- 0.39
Rat	M	0	442 +/- 49				10.9 +/- 1.4	0.67 +/- 0.13
		25	446 +/- 34				10.7 +/- 1.3	0.68 +/- 0.09
		100	454 +/- 39				10.2 +/- 1.0	0.71 +/- 0.11
		400	439 +/- 48				9.4 +/- 1.0	0.62 +/- 0.08
Rat	F	0	252 +/- 23				15.6 +/- 2.6	0.52 +/- 0.07
		25	253 +/- 21				14.5 +/- 1.9	0.46 +/- 0.05
		100	244 +/- 23				13.7 +/- 1.7	0.46 +/- 0.07
		400	250 +/- 20				14.4 +/- 2.8	0.44 +/- 0.06

Hematological data: Male and female rabbits exposed to 400 ppm EGEE sustained decreases in hemoglobin, hematocrit, and erythrocyte count. No hematological changes were observed to either sex at the lower concentrations. The only alteration noted in rats was a drop in leukocyte count from females exposed to 400 ppm. This effect was not seen in males at this concentration and is of unknown biological significance.

Hematology data for rabbits exposed subchronically to 2 -ethoxyethanol vapour:

	Male rabbits, exposure concentration				Female rabbits, exposure concentration
Variable	0	25 ppm	100 ppm	400 ppm	0	25 ppm	100 ppm	400 ppm
Hb g/dL	14.6 +/- 1.0	14.4 +/- 1.2	14.5 +/- 0.9	13.0 +/- 1.1	13.9 +/- 1.1	14.0 +/- 0.6	13.7 +/- 0.9	12.8 +/- 0.7
Hcrt %	41 +/- 3	41 +/- 3	41 +/- 3	37 +/- 3	40 +/- 3	41 +/- 1	39 +/- 2	37 +/- 2
RBC x 10^6/mm³	6.20 +/- 058	6.12 +/- 0.46	6.03 +/- 0.54	5.35 +/- 0.53	5.98 +/- 0.48	6.06 +/- 0.22	5.94 +/- 0.34	5.5 +/- 0.33

Explanations: hemoglobin (Hb), hematocrit (Hcrt), erythrocyte count (RBC)

Statistically significant differences were observed in serum biochemical variables from both species, but all are of unknown biological significance. Total protein was elevated slightly in male rabbits exposed to 400 ppm. This increase resulted from the globulin fraction. Cholesterol was lowered in females at all concentrations. In rats the only change noted was a depression of blood urea nitrogen in females at the highest concentration. Data from the urinalyses of rats were unremarkable at all exposure levels.

Gross pathological examination revealed no changes indicative of a treatment-related effect in either species. Evaluation of histopathological change in the rabbit revealed alterations in several tissues. The pathological change to the testes appeared related to EGEE exposure. Minimal to slight focal degeneration of seminiferous tubules was noted in three of ten rabbits and was characterized by loss of epithelium. Spermatogenic activity in animals exhibiting histopathologic change, as judged by overall organ morphology,

appeared normal.

A variety of incidental microscopic alterations was observed in the tissues examined from both the control and exposed rabbits. In the brain, scattered instances of focal perivascular cuffing and focal encephalitis were seen in both contral and exposed rabbits. These inflammatory lesions probably resulted from infection by Nosema sp., even though the organism was not demonstrable with H&E staining. Interstitial lymphoid infiltration and pyelitis, also associated with Nosema sp. infection, were seen occasionally in the kidneys

from both control and EGEE-treated rabbits. Extramedullary hematopoiesis and pigment deposition were seen consistently in the spleens from both control and exposed rabbits. The severity of these microscopic observations was generally comparable among the control and exposed groups. Pericholangitis and focal necrosis were frequently seen to a minimal to slight degree in the livers from both control and exposed rabbits.

Histopathological evaluation of tissues from the rat revealed no treatment-related lesions. Incidental findings comparable to both control and exposed animals were noted, e.g., extramedullary hematopoiesis, focal pneumonia, focal aveolitis, and focal bronchitis.

Histopathological lesions supportive of organ weight changes for the spleen and pituitary gland were not observed.

Discussion:

The results from this study indicate that the rabbit is the more sensitive species to subchronic exposure to EGEE vapor. Data from body weight, organ weight (males only), hematology and pathological change (males only) support a dose-related effect to both sexes of this animal exposed to 400 ppm. Animals at this concentration gained weight steadily, but lagged the control group. They also showed evidence of anemia and testicular changes characterized by degeneration of tubular epithelium. Although isolated statistically significant changes from control values occurred on all concentrations in rats, none was judged treatment-related.

The anemia observed in rabbits appears to be the result of an increase in the destruction of erythrocytes rather than adepression of erythropoiesis. No pathological change to the bone marrow was noted. The hematologic data suggest that the remaining cells are normal since no change from control values was observed in MCH, MCV, or MCHC.

The testicular effects from EGEE in rabbits were noted in a minority (3/10) high exposure of animals. These were judged to be minimal to slight. The anemia also appears to be slight. The changes from EGEE are similar qualitatively to those produced by ethylene glycol monomethyl ether (EGME). However, EGEE is clearly less potent. The ONEL from subchronic inhalation of EGEE vapor is 400 ppm in rats and 100 ppm in rabbits.

Applicant's summary and conclusion

Conclusions:

In this study the toxic potential of the test substance 2-ethoxyethanol has been evaluated via inhalation in rats and rabbits. The animals were treated 6 hours daily for 13 weeks. The derived NOELs were 400 ppm for rats and 100 ppm for rabbits.