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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:
1985
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1985
Report Date:
1985

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Hexyl CELLOSOLVE* (Ethylene glycol monohexyl ether)
- Lot/batch No.: #S-881764
- Storage condition of test material: Samples used for the study were stored in an exhaust hood in one-gallon glass bottles with Teflon R caps and blanketed with nitrogen.
- Name of test material (as cited in study report): Hexyl CELLOSOLVE* (Ethylene glycol monohexyl ether)
- Molecular formula: C6H13OCH2CH20H
- Molecular weight: 146.23
- Physical state: Water white liquid
- Analytical purity: 98.4
- Lot/batch No.: #S-881764
- Specific activity: 0.8887
- Storage condition of test material: Storage condition of test material: Samples used for the study were stored in an exhaust hood In one-gallon glass bottles with Teflon R caps and blanketed with nitrogen.
- Vapor pressure at 20 °C: < 0.1mmHg
- Boiling point: 208.1°C

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc. Kinston, NY
- Age at study initiation: Approximately 6 week
- Fasting period before study: None
- Housing: Rats were house 2/cage in stainless steel wire-mesh cages
- Diet (ad libitum): Except during exposure
- Water ( ad libitum): Except during exposure
- Acclimation period: 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): Standard conditions
- Humidity (%): Standard conditions
- Air changes (per hr): Standard conditions
- Photoperiod: (12 hrs dark / 12 hrs light):


Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
air
Remarks on MMAD:
MMAD / GSD: no data
Details on inhalation exposure:
See the attachment-1
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
See the attachment-1
Duration of treatment / exposure:
14 weeks
Frequency of treatment:
6 hours/day/week
Doses / concentrationsopen allclose all
Dose / conc.:
20 ppm (nominal)
Dose / conc.:
40 ppm (nominal)
Dose / conc.:
85 mg/m³ air (nominal)
No. of animals per sex per dose:
20/sex/exposure group
Control animals:
yes
Details on study design:
- Rationale for animal assignment: Random
- Post-exposure recovery period in satellite groups: Four week recovery period
Positive control:
None

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed prior to, during, and following each exposure for signs of toxic effects. Animals were observed once a day on weekends and holidays during the fourteen-week exposure regimen. Animals held for the four-week recovery period were observed at least once a day.
DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: prior to exposure and weekly thereafter

FOOD CONSUMPTION: Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
FOOD EFFICIENCY: No

WATER CONSUMPTION: Yes
- Time schedule for examinations: During exposure week 14 and after 4 weeks of recovery
OPHTHALMOSCOPIC EXAMINATION: Yes

- Time schedule for examinations: Prior to exposure and at sacrifice
- Dose groups that were examined: All dose groups


HAEMATOLOGY: Yes
- Time schedule for collection of blood: Prior to sacrifice during exposure week fourteen and after 4 weeks of recovery
- Anesthetic used for blood collection: Yes (identity) Methoxyflurane
- Animals fasted: Yes
- How many animals: 10/sex/exposure group
- Parameters checked in table [No.7,8, 9, 10] were examined.


CLINICAL CHEMISTRY: - Time schedule for collection of blood: Prior to sacrifice during exposure week fourteen and after 4 weeks of recovery
- Anesthetic used for blood collection: Yes (identity) Methoxyflurane
- Animals fasted: Yes
- How many animals: 10/sex/exposure group
- Parameters checked in table [No.1, 2, 3, 4] were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: During exposure week 14 and after 4 weeks of recovery
- Metabolism cages used for collection of urine: Yes
- Parameters checked in table [No.13, 14] were examined.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
Ten rats per exposure group were sacrificed on October 10 (males) and 10 (females), after receiving 66 and 67 exposures, respectively. The 4-week recovery rats, ten males per exposure group and ten females per exposure group were sacrificed after 27 and 28 post exposure days, respectively. The rats were killed by exsanguination via the brachial blood vessels following anesthesia with methoxyflurane. Gross examinations were performed and selected tissues were fixed in 10% neutral buffered formalin for possible future histologic evaluation

HISTOPATHOLOGY: Yes
Histologic evaluation was performed on selected tissues from animals in the high Concentration and control groups. No histologic evaluations were performed on the low and intermediate hexyl CELLOSOLVER groups at the end of either the exposure regimen or the recovery period.
Other examinations:
Organ weights: The brain, liver, kidneys, spleen, lungs, thymus gland, and testes (males only) from all animals were weighed at sacrifice. Organ weights were recorded as absolute weights and as a percentage of both body weight and brain weight.

Statistics:
Results of quantitative continuous variables (such as body weight changes) were intercompared among the three concentration groups and one control group by use of Bartlett's homogeneity of variance (Sokal and Rohlf, 1969), analysis of variance (ANOVA) (Sokal and Rohlf, 1969), and Duncan's multiple range tests (Snedecor and Cochran, 1967). The latter was used to delineate which exposure groups differed from the control, when F from the analysis of variance was significant. If Bartlett's test indicated heterogeneous variances, all groups were compared by ANOVA for unequal variances (Welch or Brown and Forsythe, 1974) followed if necessary by t-tests. Corrected Bonferroni probabilities were used for t-test comparisons. Statistical procedures for hematologic continuous variables were similar and details of the procedures can be found
in the Clinical Pathology Report (Appendix 2). The fiducial limit of 0.05 (two-tailed) was used as the critical level of significance for all comparisons.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
The principal sign observed in males that was considered to be exposure related was a urogenital wetness in the 71 ppm group. Urogenital wetness was also observed in female rats, but in a dose-related manner among all exposed groups. On a daily basis, the urogenital wetness was principally observed after the exposure rather than in the morning (before the exposure). The urogenital wetness was primarily observed beginning during week 6 of the study and continued until the termination of exposures. Also, beginning about week 9 and continuing until the termination of exposures, rats of the 71 ppm group were observed lying on their sides during the daily exposures. There were no significant signs observed during the recovery period.
Mortality:
no mortality observed
Description (incidence):
There were no mortalities during the study.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Consistent statistically significant decreases in body weight gain were observed in the 71 ppm males (weeks 5-12) and females (weeks 5-14), and in the 41 ppm females (weeks 6-12). There were no exposure-related decreases in body weight gain observed in any group during the recovery period. There were no statistically significant differences in absolute body weight for any of the groups at the end of the exposure or recovery period
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Statistically significant Increases in food and water consumption were observed in the 71 ppm males at the end of the exposure regimen (day 93). A significant increase in food consumption was observed in the 71 ppm females at the end of both the exposure regimen (day 94) and the recovery period (day 122). Other statistically significant differences were considered to be spurious as they were observed in the 20 ppm group with no effects observed in the 41 ppm group, i.e., no dose-response effect
Food efficiency:
not examined
Ophthalmological findings:
no effects observed
Description (incidence and severity):
There were no exposure-related ocular effects observed during the study.
Haematological findings:
no effects observed
Description (incidence and severity):
There were no biologically significant alterations were observed in hematology parameters for rats monitored at 14 weeks or following a four week recovery period.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
There were no biologically significant alterations were observed in serum chemistry parameters for male rats monitored at 14 weeks or following a four week recovery period.
However, decreases in transaminases (AST and ALT) and sorbitol dehydrogenase (SDH), and Increases in alkaline phosphatase (ALP) were observed at the end of the exposure period for female rats exposed to 71 ppm vapor. No similar effects were observed on these enzyme levels at the end of the recovery period for female rats exposed to 71 ppm. However, there was a statistically significant increase in gamma-glutamyl -transferase for the 71 ppm females at the end of the recovery period.
Urinalysis findings:
no effects observed
Description (incidence and severity):
There were no biologically significant alterations were observed in urinalysis parameters for rats monitored at 14 weeks or following a four week recovery period.
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
There were two organs for which possible exposure-related effects were observed. For males, statistically significant increases in absolute and relative kidney weights were observed for the 41 and 71 ppm groups at the end of the exposure regimen. A statistically significant Increase in the kidney/body weight ratio was also observed for the 20 ppm males. Similar effects were not observed for males after the recovery period. Females of the 71 ppm group exhibited slight Increases in absolute and relative kidney weights, with the kidney/body weight value achieving statistical significance. Absolute and relative liver weights were statistically significantly increased for females of the 71 ppm group at the end of the exposure regimen.

The liver/body weight ratio was also significantly increased for the 41 ppm group females. However, there were apparent dose-related Increases in absolute and relative liver weights for all exposed groups of females at the end of the exposure regimen. Absolute and relative liver weights were also significantly increased at the end of the recovery period for the 71 ppm females. For males, statistically significant Increases in relative (both to body and brain weight) liver weights were observed for the 71 ppm group. However, dose-related increases were evident for the liver/brain weight data for exposed males. Liver/body weight ratios were statistically significantly increased for the 41 and 71 ppm males at the end of the recovery period.
Gross pathological findings:
no effects observed
Description (incidence and severity):
There were no gross lesions found that were attributable to exposure to the test substance.
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
There were no histologic lesions observed that were attributable to the test substance vapor exposure.
Histopathological findings: neoplastic:
not examined

Effect levels

Key result
Dose descriptor:
NOAEL
Effect level:
41 ppm
Sex:
male/female
Basis for effect level:
other: no adverse effect observed

Target system / organ toxicity

Critical effects observed:
no

Any other information on results incl. tables

None

Applicant's summary and conclusion

Conclusions:
Based on the data from this study, 41 ppm is considered to be the concentration at which no biologically significant toxic effects were observed. Although the toxic effects observed at 71 ppm were generally mild, the spectrum of body weight, clinical chemistry, and organ weight effects, some of which persisted into the recovery period, are considered to be treatment related and thus to be biologically relevant in assessing potential health effects from this material.

Executive summary:

Four groups, each consisting of 20 Fischer 344 rats per sex, were exposed for 6 hours per day, 5 days per week, for 14 weeks to the vapor of ethylene glycol hexyl ether) at target concentrations of 0 (control), 20, 40, or 85 ppm and followed by 4 week recovery period.. Actual mean concentrations obtained for this study were 20, 41, and 71 ppm ethylene glycol hexyl ether.

 

Rats were received from breeding Laboratories. Rats were kept for acclimatization for 5 days. At study initiation rats were of approximately 9 weeks old. Rats were housed 2/cage in stainless steel cages with wire mash bottoms. Rats were provided ad libitum feed and municipal water except during exposure. The animals were kept on a 12-hour photoperiod throughout the study.

 

Monitors for toxic effects included clinical observations, body weight, food and water consumption, ophthalmology, hematology, clinical chemistry, urinalysis, organ weights, and macroscopic and microscopic tissue evaluations.

  

The principal sign observed in males that was considered to be exposure related was a urogenital wetness in the 71 ppm group. Urogenital wetness was also observed in female rats, but in a dose-related manner among ethylene glycol hexyl ether-exposed groups. On a daily basis, the urogenital wetness was principally observed after the exposure rather than in the morning (before the exposure). The urogenital wetness was primarily observed beginning during week 6 of the study and continued until the termination of exposures. Also, beginning about week 9 and continuing until the termination of exposures, rats of the 71 ppm group were observed lying on their sides during the daily exposures. There were no significant signs observed during the recovery period. There were no mortalities during the study.

 

Consistent statistically significant decreases in body weight gain were observed in the 71 ppm males (weeks 5-12) and females (weeks 5-14), and in the 41 ppm females (weeks 6-12). There were no exposure-related decreases in body weight gain observed in any group during the recovery period. There were no statistically significant differences in absolute body weight for any of the groups at the end of the exposure or recovery period.

 

Statistically significant Increases in food and water consumption were observed in the 71 ppm males at the end of the exposure regimen (day 93). A significant increase in food consumption was observed in the 71 ppm females at the end of both the exposure regimen (day 94) and the recovery period (day 122). Other statistically significant differences were considered to be spurious as they were observed in the 20 ppm group with no effects observed in the 41 ppm group, i.e. no dose-response effect.

 

There were no exposure-related ocular effects observed during the study. There were no biologically significant alterations were observed in hematology parameters for rats monitored at 14 weeks or following a four week recovery period. There were no biologically significant alterations were observed in urinalysis parameters for rats monitored at 14 weeks or following a four week recovery period. There were no biologically significant alterations were observed in serum chemistry parameters for male rats monitored at 14 weeks or following a four week recovery period.

However, decreases in transaminases (AST and ALT) and sorbitol dehydrogenase (SDH), and Increases in alkaline phosphatase (ALP) were observed at the end of the exposure period for female rats exposed to 71 ppm ethylene glycol hexyl ether vapor. No similar effects were observed on these enzyme levels at the end of the recovery period for female rats exposed to 71 ppm of ethylene glycol hexyl ether vapor. However, there was a statistically significant increase in gamma-glutamyl-transferase for the 71 ppm females at the end of the recovery period.

 

Increased absolute and/or relative liver and kidney weights in both sexes of the 71 ppm group and, to a lesser extent, in the 41 ppm group. However, there were no exposure-related macroscopic or microscopic abnormalities found in this study. There were no exposure-related effects on the potential primary target tissues for glycol ethers of blood and testes. The changes observed at 41 ppm and below were not considered to be biologically significant, while the effects observed at 71 ppm, although not severe, were considered to be related to exposure to ethylene glycol hexyl ether vapor and thus to have biological relevance.

Based on the data from this study, 41 ppm is considered to be the concentration at which no biologically significant toxic effects were observed. Although the toxic effects observed at 71 ppm were generally mild, the spectrum of body weight, clinical chemistry, and organ weight effects, some of which persisted into the recovery period, are considered to be treatment related and thus to be biologically relevant in assessing potential health effects from this material.