1-(1-methyl-2-propoxyethoxy)propan-2-ol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

Minor deviations were observed and reported and these did not negatively impact the quality or integrity of the data nor the outcome of the study.

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

Minor deviations were observed and reported and these did not negatively impact the quality or integrity of the data nor the outcome of the study.

Principles of method if other than guideline:

not applicable

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1-(1-methyl-2-propoxyethoxy)propan-2-ol

EC Number:

249-949-4

EC Name:

1-(1-methyl-2-propoxyethoxy)propan-2-ol

Cas Number:

29911-27-1

Molecular formula:

C9H20O3

IUPAC Name:

1-(1-methyl-2-propoxyethoxy)propan-2-ol

Details on test material:

- Name of test material (as cited in study report): Dipropylene Glycol n-Propyl Ether
- Physical state: clear colorless liquid
- Analytical purity: 99.06%
- Expiry date: 31 March, 2006
- Composition of test material, percentage of components: A purity of 99.05% ± 0.09 % as the sum of five isomers as determined by GC/FID area percent, corrected for water was reported for the sample.
- Isomers composition: same as above
- Lot/batch No.: SC2455R5L3
- Stability under test conditions: stable during test conditions
- Storage condition of test material: stored at room temperature
- Other: The water content was determined to be 0.29% ± 0.02% by Karl Fischer coulometric titration. GC/MS and FTIR spectra were consistent with the proposed structure of DPnP.
- Synonym: DOWANOL DPnP

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Covance Research Products, Inc., Denver, Pennsylvania
- Age at study initiation: 5.5 months old upon receipt
- Weight at study initiation: 3084 g to 4442 g
- Housing: Upon arrival, all rabbits were housed individually in clean, stainless steel cages suspended above ground corncob bedding (Pel-O’Cobs®; The Andersons, Industrial Products Division, Maumee, Ohio). The bedding was changed at least twice each week. Nesting material was not required, as the females were euthanized prior to the date of expected parturition. Animals were maintained in accordance with the Guide for the
Care and Use of Laboratory Animals (National Research Council, 1996). The animal facilities at WIL Research Laboratories, LLC are fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC International).
- Diet (e.g. ad libitum): The basal diet (PMI Nutrition International, LLC, Certified Rabbit LabDiet® 5322) was offered 3 times at 25 g on the day of arrival, 3 times at 50 g on the day after arrival and ad libitum on all subsequent days until euthanasia.
- Water (e.g. ad libitum): Reverse osmosis-purified (on-site) drinking water, delivered by an automatic watering system was provided ad libitum during the study.
- Acclimation period: not specified in the report

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 66 ± 5°F (19 ± 3°C), Actual mean daily temperature ranged from 65.6°F to 66.5°F (18.7°C to 19.2°C)
- Humidity (%): 50 ± 20% relative humidity, Actual mean daily relative humidity ranged from 43.5% to 54.8%
- Air changes (per hr): Air handling units were set to provide approximately 10 fresh air changes per hour.
- Photoperiod (hrs dark / hrs light): Light timers were calibrated to provide a 12-hour light (6 a.m. to 6 p.m.)/12-hour dark photoperiod

Administration / exposure

Route of administration:

dermal

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST SITE
- Area of exposure: The appropriate volume of the test or control article was applied evenly over the shaved, intact dorsal skin of each animal (approximately 10 cm x 15 cm) using a syringe and stainless steel cannulae (16-gauge).
- % coverage: The area dosed corresponded to approximately 5.3% to 7.2% of the body surface area (cm2).
- Type of wrap if used: A bandage of absorbent gauze was placed over the dosing area followed by a layer of non-absorbant material (polyethylene plastic). These 2 layers were held in place with tape. The treated area and the 2 layers of material were then secured by wrapping the torso with gauze bandaging and secured with Durapore® wrap.
- Time intervals for shavings or clipplings: One day prior to the initiation of dose administration and throughout the study as necessary (at least 1 time each week), a section slightly larger than the dosing area of the scapular and lumbar regions of each rabbit was shaved with Oster® small animal clippers.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Following the 6-hour exposure period each day, the collars and wrappings were removed. The test sites were gently washed with disposable paper towels and deionized water to remove any residual test article, and then gently dried.
- Time after start of exposure: 6 hours/day

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): The dosage volumes were 1.1, 0.55, 0.83 and 1.1 mL/kg for the control, 500, 750 and 1000 mg/kg/day groups, respectively.

USE OF RESTRAINERS FOR PREVENTING INGESTION: yes. The duration of the exposure was 6 hours, during which Elizabethan collars were
applied to each animal to prevent ingestion of the test article and/or wrappings.

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

As the test article was administered undiluted, analyses to confirm stability, homogeneity and concentration of the test article were not conducted.

Details on mating procedure:

- Impregnation procedure: purchased timed pregnant

Duration of treatment / exposure:

The control and test article were administered by dermal application for 6 hours, once daily during gestation days 6-28.

Frequency of treatment:

The control and test article were administered by dermal application for 6 hours, once daily during gestation days 6-28.

Duration of test:

The control and test article were administered by dermal application for 6 hours, once daily during gestation days 6-28.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

500 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

750 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

25 time mated rabbits per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on the results of a range finding study, there was no maternal toxicity or embryo/fetal lethality observed at the limit dose of 1000 mg/kg/day.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All rabbits were observed twice daily, once in the morning and once in the afternoon, for moribundity and mortality. Animals were also observed for signs of toxicity approximately 1-2 hours following dose administration.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Individual detailed clinical observations were recorded from the day of receipt through gestation day 29 (prior to dose administration during the treatment period).

DERMAL OBSERVATIONS: Yes
- Time schedule: Application sites were examined for erythema, edema, scaling, fissuring and other dermal findings daily within approximately 1 hour (target time between 30 and 60 minutes) after the end of each 6-hour exposure

BODY WEIGHT: Yes
- Time schedule for examinations: Individual maternal body weights were recorded on gestation days 0 (by supplier), 4 and 6-29 (daily).

FOOD CONSUMPTION: Yes
- Time schedule: Individual food consumption was recorded daily on gestation days 4-29. Food intake was reported as g/animal/day and g/kg/day for the corresponding body weight change intervals and also for gestation days 6-9, 9-12, 12-15, 15-18, 18-21, 21-25, 25-29 and 6-29.

WATER CONSUMPTION: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 29
- Organs examined: rabbits were euthanized on gestation day 29 by an intravenous injection of sodium pentobarbital via the marginal ear vein. The thoracic, abdominal and pelvic cavities were opened by a ventral mid-line incision, and the contents were examined. In all instances, the post mortem findings were correlated with the ante mortem comments and any abnormalities were recorded.

OTHER: Liver weights were recorded for all does. Maternal tissues were preserved in 10% neutral-buffered formalin for possible future histopathologic examination only as indicated by the gross findings. The carcass of each female was then discarded.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Uteri with no macroscopic evidence of implantation were opened and subsequently placed in 10% ammonium sulfide solution for detection of early implantation loss.

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [all per litter]
- Skeletal examinations: Yes: [all per litter]
- Head examinations: Yes: [half per litter]

Statistics:

Standard statistical procedures were used.

Indices:

Postimplantation loss, viable fetuses affected/litter

Historical control data:

yes

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

effects observed, treatment-related

Description (incidence and severity):

Slight to severe scaling and slight fissuring was noted for a majority of animals in the 1000 mg/kg/day group. The incidence of these findings was highest mid-way through dosing, and decreased in severity and incidence generally throughout the remainder of the study. The control, 500 and 750 mg/kg/day groups also experienced slight scaling, but the incidence was greatly reduced compared to the 1000 mg/kg/day group. Moderate erythema was noted in 1 and 4 females in the 750 and 1000 mg/kg/day groups, respectively. Slight erythema was noted in all treatment groups, with the highest occurrence in the 1000 mg/kg/day group. The incidence of very slight erythema (barely perceptible) was similar between the control and 500 mg/kg/day group; however, this finding was noted up to approximately twice as often in the 750 and 1000 mg/kg/day groups throughout the treatment period. Very slight to slight edema was noted for multiple females in the 500, 750 and 1000 mg/kg/day groups, compared to a single occurrence of very slight edema in the control group; no dose-related trend was evident. The dermal findings in this study were generally considered test article-related, but because the severity and incidence decreased substantially or were absent by the end of the dose administration period, the dermal findings were not considered adverse.

Mortality:

no mortality observed

Description (incidence):

All animals survived to the scheduled necropsy.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Maternal developmental toxicity

Details on maternal toxic effects:

Other than the dermal irritation described above, no test article-related clinical or macroscopic findings were noted at any dose level. Mean maternal body weights, body weight changes, net body weights, net body weight changes, gravid uterine weights and food consumption were unaffected by test article administration.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Based on:

test mat.

Remarks on result:

not determinable due to absence of adverse toxic effects

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Anogenital distance of all rodent fetuses:

not specified

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

not examined

Other effects:

no effects observed

Details on embryotoxic / teratogenic effects:

Intrauterine growth and survival in the test article-treated groups were similar to the control group. There were no test article-related malformations or developmental variations observed in any fetus evaluated in this study.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

no

Any other information on results incl. tables

None

Applicant's summary and conclusion

Conclusions:

Based on the results of this study, the dermal application of 1000 mg/kg/day (the limit dose based on OPPTS 870.3700 Guidelines) was considered to be the no-observed-adverse-effect level (NOAEL) for maternal systemic toxicity; however, dermal irritation (local toxicity) was transiently observed at all dosage levels. A dosage level of 1000 mg/kg/day was considered to be the NOAEL for prenatal development when DPnP was administered by dermal exposure to pregnant rabbits.

Executive summary:

The objective of the study was to determine the potential maternal toxicity (local and systemic) and/or prenatal developmental toxicity of the test article, dipropylene glycol n-propyl ether (DPnP), when administered by dermal exposure to pregnant rabbits throughout the period of major organogenesis up to a limit dose of 1000 mg/kg/day and to determine a NOAEL (no-observed-adverse-effect level) for maternal toxicity and developmental toxicity.

All animals survived to the scheduled necropsy. Slight to severe scaling and slight fissuring was noted for a majority of animals in the 1000 mg/kg/day group. The incidence of these findings were highest mid-way through dosing, and decreased in severity and incidence generally throughout the remainder of the study. The control, 500 and 750 mg/kg/day groups also experienced slight scaling, but the incidence was greatly reduced compared to the 1000 mg/kg/day group. Moderate erythema was noted in 1 and 4 females in the 750 and 1000 mg/kg/day groups, respectively. Slight erythema was noted in all treatment groups, with the highest occurrence in the 1000 mg/kg/day group. The incidence of very slight erythema (barely perceptible) was similar between the control and 500 mg/kg/day group; however, this finding was noted up to approximately twice as often in the 750 and 1000 mg/kg/day groups, respectively, throughout the

treatment period. Very slight to slight edema was noted for multiple females in the 500, 750 and 1000 mg/kg/day groups, compared to a single occurrence of very slight edema in the control group; no dose-related trend was evident. No maternal systemic toxicity (clinical observations, body weight, food consumption, macroscopic findings or liver weights) was observed at any dosage level in this study. Dermal irritation (local toxicity) was transiently observed at all dosage levels. Intrauterine growth and survival in the test article-treated groups were similar to the control group. There were no test article-related malformations or developmental variations observed in any fetus evaluated in this study.

Based on the results of this study, the dermal application of 1000 mg/kg/day (the limit dose based on OPPTS 870.3700 Guidelines) was considered to be the no-observed-adverse-effect level (NOAEL) for maternal systemic toxicity; however, dermal irritation (local toxicity) was transiently observed at all dosage levels. A dosage level of 1000 mg/kg/day was considered to be the NOAEL for prenatal development when DPnP was administered by dermal exposure to pregnant rabbits.