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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study well reported. Compared to a standard OECD protocol: .No opthamology reported. No food consumption reported. Limited clinical chemistry measurements. No indication of examination of organs other than those specifically commented on but none are known to be targets of this substance. Published study does not include tabulation of non-signficant data.

Data source

Reference
Reference Type:
publication
Title:
Ethylene glycol methyl ether I. Subchronic vapour inhalation study with rats and rabbits.
Author:
Miller RR, Ayres JA, Young JT et al
Year:
1983
Bibliographic source:
Fundam Appl Toxicol, 3:49-54

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
Deviations:
yes
Remarks:
, use of rabbits, no opthalmology
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Analytical purity: Gas chromatographic analysis showed a purity of 99.78-99.93%.
- supplied by Dow Chemical USA.

Test animals

Species:
rabbit
Strain:
New Zealand White
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Langshaw Farms, Augusta, Michigan.
- Age at study initiation: 6-7 months
- Housing: Animals were individually tagged and randomly assigned to groups and allowed to acclimatize to chambers, singly caged.
- Diet: Purina certified chow (Raiston Purina CO, St Louis, Missouri) ad libitum except during exposure.
- Water: ad libitum except during exposure.

ENVIRONMENTAL CONDITIONS
- Temperature: 72F
- Humidity: 40-69% RH when not in the exposure chamber.
- Photoperiod: 12hr light/dark cycle.

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure:
whole body
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The exposure chambers were 14.5m3 in volume with, stainless steel ceiling, epoxy resin walls/floors, 2500l/min air flow, temperature and RH as described.
- Method of conditioning air: Vapour was generated by metering liquid flow into evaporation tubes through which air heated to 120F using a compressed air flameless torch was passed. Nominal concentrations of methoxyethanol were calculated by weight loss to the evaporator
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Measurement every 30-60mins using a daily calibrated Miran infra red gas analyzer at 8.8u wavelength. Analyser calibrated daily. Actual exposures found to be within 2% of nominal.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
Exposure was 6hrs/day, 5 days/week.
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 30, 100, 300ppm nominal
Basis:

No. of animals per sex per dose:
5 per sex
Control animals:
yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: at the start and then weekly.

HAEMATOLOGY: Yes
- Haematological analysis was performed on all surviving animals at weeks 4 and 12.


CLINICAL CHEMISTRY: Yes
- Clinical chemistry parameters were analysed from each surviving animal at week 13.
Sacrifice and pathology:
All rabbits were weighed then necropsied following final exposure. Sacrifice was by CO2 asphyxiation. Weights of liver, spleen, brain, kidneys, thymus and testes were recorded. Lungs were distended to normal volume by tracheal infusion of neutral phosphate buffered 10% formalin. All other dissected tissues were preserved in the same solution except the testes which were preserved in Bouin’s fixative. Representative sections of the complete set of tissues from all exposure groups were sectioned and processed for light microscopic examination after H&E staining.
Statistics:
Body weights, organ weights, haematology data, urine specific gravity, clinical chemistry data: analysed by Bartlett’s test (p<0.01) and either parametric ANOVA (p<0.10) or Dunnett’s test (p<0.05) or a non-parametric ANOVA (p<0.01) and Wilcoxon’s test (p<0.05) according to whether the group variance were homogenous or non-homogeneous respectively.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
Measured atmospheric concentrations showed that all exposures were within 2% of nominal values. Four animals (2M/2F) in the top dose groups died or became moribund and were sacrificed during the study. Two females were lost from the intermediate dose, one after 9 days was sacrified due to an ear infection and a second was found dead after 21 days. The relationships of these deaths to exposure was uncertain.

BODY WEIGHT AND WEIGHT GAIN. ORGAN WEIGHTS
Mean body weights of both males and females in the top dose group and females in the intermediate dose group tended to be lower than controls but were not statistically significant. Gross changes were seen in males at all concentrations and females at the medium and high doses Both sexes in the high dose group showed decreased amounts of: abdominal fat, mediastinal tissue (including fat and thymic tissue), lymphoid tissue in the cecal appendix and sacculus rotundus. The testes of males showed effects at all doses. At 300ppm they were small and flaccid; slight to moderate decreases in size were seen in 4/5 rabbits in the medium dose group and 2/5 in the low dose group. At 100ppm a single female showed decreased lymphoid tissue in the cecal appendix and sacculus rotundus that was considered treatment related. Weights of thymus were also significant at 300ppm in both sexes and testes in males. The weights of testes in the male rabbits at 100ppm were lower than controls and, although not statistically significant, was attributed to exposure. Reductions in liver weight were seen but these were not consistent nor statistically significant and could be attributed to body weight reduction rather than hepatotoxicity.


HAEMATOLOGY
At 300ppm, reductions were seen in mean white blood counts, platelet counts, packed cell volumes and haemoglobin concentrations. These changes were apparent from week 4 but did not increase in severity from this time point. No effects were seen in differential white blood cell counts and no effects were seen at all in the two lower dose groups.

CLINICAL CHEMISTRY
All values for clinical chemistry (total protein, albumin, globulins) were normal.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathology of the testes showed microscopic lesions at all three exposure concentrations in males which was dose related in both incidence and severity. In all surviving rabbits at 300ppm, degeneration was diffuse and severe with virtually every tubule affected. Sertoli cells and an occasional spermatogonium were all that remained in the shrunken tubules. At 100ppm, some tubules were relatively normal whilst others contained no germinal elements at all. Two rabbits at this dose level had normal testes. At 30ppm, only one rabbit showed degenerative changes to the testes where the germinal epithelium was thinner than normal and had a complete complement of germinal stages but few spermatozoa. Other less significant changes attributed to treatment were seen in both males and females. Effects attributed to treatment included lymphoid atrophy of the thymus and gut associated lymphoid organs (especially the cecal appendix), decreased hepatocyte size with reduced microvesiculation characteristics of glycogen depletion. These effects were seen primarily in the high dose groups but also in a few animals (both sexes) from the 100ppm group.

Effect levels

open allclose all
Dose descriptor:
NOAEC
Effect level:
< 30 ppm
Sex:
male
Basis for effect level:
other: testes (size, histology) - marginal
Dose descriptor:
NOAEC
Effect level:
100 ppm
Sex:
male/female
Basis for effect level:
other: thymus weight, haematology

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Executive summary:

A 13 week sub-chronic study examined the inhalation toxicity of methoxyethanol vapour in rabbits when exposed to concentrations up to 300ppm. Some mortality was seen in the 100 and 300 ppm exposure groups and some were sacrificed when moribund during the study. Body weights as well as thymus and testicular weights in the 300 ppm group were reduced as a result of the exposures. Hematologic changes occurred at 300 ppm but no changes in clinical chemistry were seen in any group. Gross lesions at 300 ppm included decreased size of thymus in both sexes, decreased abdominal fat, and small flaccid testes in males. In addition there was decreased lymphoid tissue in some animals, as well as a slight-to-moderate decrease in size of testes in 4 of 5 rabbits in the 100 ppm group and in 2 of 5 rabbits exposed to 30 ppm. Treatment-related microscopic lesions included degenerative changes in germinal epithelium of testes in all male rabbits in the 300 ppm group, as well as in 3 of 5 rabbits in the 100 ppm group and 1 of 5 male rabbits in the 30 ppm group. The only effects attributed to exposure to 30 ppm were slight microscopic changes in testes of 1 of 5 male rabbits.

Synopsis:

NOAEL: <30ppm (males - testes); females