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Toxicity to reproduction: other studies

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Endpoint:
toxicity to reproduction: other studies
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted as per OECD TG 412, EC Method B.8 and in accordance with the Principles of Good Laboratory Practice (GLP).
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report Date:
2005

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
other: OECD Guideline 412 (Repeated Dose Inhalation Toxicity: 28/14-Day
Deviations:
yes
Remarks:
(Deviations observed during the conduct of the range and the main study were not considered to have influenced the integrity and validity of the study results)
Qualifier:
according to
Guideline:
other: EU Method B.8 (Repeated Dose (28 Days Toxicity (Inhalation)
Deviations:
yes
Remarks:
same as above
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Type of method:
in vivo

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): n-dibutylether
- Physical state: colourless volatile liquid
- Analytical purity: range finding - > 99.3%, main study - > 99.76%
- Lot/batch No.: range finding - 0000093881, main study - 0000100437
- Expiration date of the lot/batch: range finding - 19 december 2004, main study - 31 July 2005
- Storage condition of test material: ambient temperature, dark, protected from air

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Deutschland, Sulzfield, Germany
- Age at study initiation: 7-9 weeks
- Weight at study initiation: mean male weight - 226 gram, mean female weight - 175 gram
- Housing: standard housing conditions
- Diet (e.g. ad libitum): ad libitum from the arrival of rats until the end of the study, except during exposure and during overnight fasting prior to necropsy
- Water (e.g. ad libitum): ad libitum from the arrival of rats until the end of the study, except during exposure and during overnight fasting prior to necropsy
- Acclimation period: 9 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 30-70%
- Air changes (per hr): 10 air changes/hour
- Photoperiod (hrs dark / hrs light): 12 hours light/dark cycle

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure (if applicable):
nose only
Vehicle:
air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were exposed to the test atmosphere in noe-only exposure units, each unit consisted of a cylindrical column, surrounded by a transparent cylinder. The column consisted of a top assembly with the inlet of the test atmosphere, one or two rodent tube sections and at the bottom the base assembly with the exhaust port.
- Method of holding animals in test chamber: Each rodent tube section had 20 ports for animal exposure. The animals were secured in plastic animal holders (Battelle), positioned radially through the outer cylinder around the central column (males and females alternated). Several empty ports were used for test atmosphere sampling and measurement of temperature and relative humidity. The extra remaining ports were closed. Only the nose of the rats protruded into the interior of the column. Animals were rotated on a weekly basis in such a way that at the end of the exposure period, the animals were at about the initial location again. The units were illuminated externally by normal laboratory TL-lighting.
- Source and rate of air: The test atmosphere for each exposure level was generated by passing humidified air for each exposure unit through glass evaporators. The test material was pumped as a liquid in the evaporators using syringe pumps. The air streams measured by rotameters were directed to the exposure units. At the bottom of the units the test atmospheres were exhausted. The rotameters and the syringe pumps were read out and recorded at regular intervals (approximately bi-hourly, i.e. 3 times a day). The rotameters were calibrated at 3 settings in triplicate.
- Temperature, humidity, pressure in air chamber: 22 ± 3 °C, 30-70% relative humidity

TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of n-dibutylether in the test atmosphere was measured by infrared analysis at 3.4 µm. The response of the analyser was recorded by an analogue recorder. Also, the concentration of n-dibutylether in the test atmospheres was measured by total carbon analysis for the low and mid concentration test atmospheres, the response was recorded by an analogue recorder.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The mean concentrations were 151 ± 3, 497 ± 3 and 1497 ± 3 mg n-dibutylether/m3
Duration of treatment / exposure:
28 days followed by a 2-week recovery period
Frequency of treatment:
daily 6 hours/day, 5 days/week for 4 weeks (a total of 20 exposures) daily during the exposure period.
Duration of test:
28 days followed by a 2-week recovery period
Doses / concentrations
Remarks:
Doses / Concentrations:
150, 500 and 1500 mg/m³ (actual concentration)
Basis:
other: mean actual concentrations were 151 ± 3, 497 ± 3 and 1497 ± 3 mg n-dibutylether/m3, mean nominal concentrations were 179, 538 and 1553 mg/m3
No. of animals per sex per dose:
5 males + 5 females/test group and 5 males + 5 females - control and 1500 mg/m3 reversal group

Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: based on the results of the range finding study with exposure concentrations of 0, 1000, 3000 and 10000 mg/m3 (reduced to 6500 mg/m3 since ataxia was observed in the exposed males after first exposure to 10000 mg/m3 of n-dibutylether)
- Rationale for animal assignment: computer randomization taking body weights into account
- Post-exposure recovery period in satellite groups: 2 weeks - control and high dose reversal groups
Statistics:
Standard statistical methods were employed

Results and discussion

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
1 500 mg/m³ air
Based on:
test mat.
Sex:
male
Basis for effect level:
other: based on overall effects
Dose descriptor:
NOAEL
Effect level:
500 mg/m³ air
Based on:
test mat.
Sex:
female
Basis for effect level:
other: based on body weight reduction noted in the first exposure week at the highest dose of 1500 mg/m3
Dose descriptor:
LOAEL
Effect level:
1 500 mg/m³ air
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: based on overall effects

Observed effects

No substance related effects were seen on reproductive organs. For detailed study description refer to 7.5.2 - KS_Repeated dose 28-days: inhalation_Wacker_2005

Any other information on results incl. tables

There were no concentration-related effects on relative and absolute organ weights of testes, epididymides, ovaries and uterus. Also there were no substance-related macroscopical or histopathological changes in testes, epididymides, prostata, seminal vesicles, coagulating glands, ovaries, uterus, vagina and mammary gland.

Applicant's summary and conclusion

Conclusions:
There were no concentration-related effects on relative and absolute organ weights of testes, epididymides, ovaries and uterus. Also there were no substance-related macroscopical or histopathological changes in testes, epididymides, prostata, seminal vesicles, coagulating glands, ovaries, uterus, vagina and mammary gland.

Overall, the results of the study, it can be concluded that exposure to concentrations of 150, 500 and 1500 mg of n-dibutylether/m3 concentrations did not result in treatment related effects in male rats and only in limited effects in females exposed to 1500 mg/m3. Exposure to 1500 mg/m3 resulted in a temporary body weight loss in these females during the first exposure week. After this week, including the 14-day recovery period, growth was comparable to the control group. This weight loss can be considered as a temporaray effect and the highest expsoue of 1500 mg/m3 can therefore be considered as the Low observed adverse effect level (LOAEL) for both the sexes. The No observed adverse effect level (NOAEL) for male rats can be considered as 1500 mg/m3 and for female rats the mid dose of 500 mg/m3.
Executive summary:

The 28 -day inhalation toxicity study was conducted according to OECD TG 412, EC Method B.8 and in accordance with the Principles of Good Laboratory Practice (GLP). Groups of 5 male and 5 female rats were exposed to n-dibutylether at concentrations of 150, 500 and 1500 mg/m3 (based on the results of a 7 -day inhalation toxicity study at concentrations of 1000, 3000 and 10000 mg/m3 (later reduced to 6500 mg/m3 as all animals of 10000 mg/m3 exhibited signs of ataxia). Also, a concurrent control was used in the study along with the control and the 1500 mg/m3 reversal group.

There were no exposure related clinical signs, haematology, clinical chemistry and urinalysis and organ weights. In addition treatment realted changes were not evident in gross pathology of all the animals of the main study and the reversal group and no evidence of any treatment related histopathjological changes in any organs. The only exposure related change noted was a decrease in the body weight gain of the high dose group during the first week of exposure, thereafter the weekly body weight gain was comparable to the other groups including control.

There were no concentration-related effects on relative and absolute organ weights of testes, epididymides, ovaries and uterus. Also there were no substance-related macroscopical or histopathological changes in testes, epididymides, prostata, seminal vesicles, coagulating glands, ovaries, uterus, vagina and mammary gland.

Overall, the results of the study, it can be concluded that exposure to concentrations of 150, 500 and 1500 mg of n-dibutylether/m3 concentrations did not result in treatment related effects in male rats and only in limited effects in females exposed to 1500 mg/m3. Exposure to 1500 mg/m3 resulted in a temporary body weight loss in these females during the first exposure week. After this week, including the 14-day recovery period, growth was comparable to the control group. This weight loss can be considered as a temporaray effect and the highest expsoue of 1500 mg/m3 can therefore be considered as the Low observed adverse effect level (LOAEL) for both the sexes. The No observed adverse effect level (NOAEL) for male rats can be considered as 1500 mg/m3 and for female rats the mid dose of 500 mg/m3.