Bis(2-methoxyethyl) ether

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3. July 1984 - 18 April 1985

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

no data on food consumption and no. of corpaora lutea

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Bis(2-methoxyethyl) ether

EC Number:

203-924-4

EC Name:

Bis(2-methoxyethyl) ether

Cas Number:

111-96-6

Molecular formula:

C6H14O3

IUPAC Name:

1-methoxy-2-(2-methoxyethoxy)ethane

Constituent 2

Reference substance name:

Diethylene glycol dimethyl ether

IUPAC Name:

Diethylene glycol dimethyl ether

Constituent 3

Reference substance name:

Diglyme

IUPAC Name:

Diglyme

Constituent 4

Reference substance name:

Bis(2-methoxyethyl)ether

IUPAC Name:

Bis(2-methoxyethyl)ether

Details on test material:

Source: Aldrich Chemical Company
Lot: 1617HK
Purity: <99%

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dutchland Inc., Denver, PA, USA
- Age at study initiation: approx. 6 months
- Weight at study initiation: 3100-4740 g
- Housing: singly in stainless steel cages with mesh flooring (min. 18"x24"x18" - max. 24"x24"x20)
- Diet (e.g. ad libitum): Purina Certified Rabbit Chow (5322), ad libitum
- Water (e.g. ad libitum): deionized/filtered water, ad libitum
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Humidity: 53%
- Temperature: 68°F
- Air changes (per hr): 12 - 14 times per hour
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Artificially inseminated, timed-pregnant New Zealand White rabbits were dosed daily with Diglyme or vehicle on gestation day (gd) 6 though 19. Treatment wass administered by gavage. A dose volume of 3.0 mL/kg bw was used. The volume administered to each animal was adjusted according to daily body weight taken just prior to dosing on gd 6 through 19.

A. First preliminary study: Diglyme was administered at dose levels of 0, 100, 200, and 400 mg/kg bw/d (4 animals/dose level)
B. Second preliminary study: Diglyme was administered at dose levels of 0, 25, 50, 100, and 150 mg/kg bw/d (6 animals/dose level)
C. Main study dose levels: 0, 25, 50, 100, and 175 mg/kg bw/d at 15-25 animals/dose level)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Gas chromatography

Details on mating procedure:

atrificially inseminated

Duration of treatment / exposure:

gd 6 through 19 (14 days)

Frequency of treatment:

daily

Duration of test:

duration of treatment: 14 days
termination: gd 30

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

25 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

50 mg/kg bw/day

Doses / concentrations 4

Dose / conc.:

100 mg/kg bw/day

Doses / concentrations 5

Dose / conc.:

175 mg/kg bw/day

No. of animals per sex per dose:

25 - 32

Control animals:

yes, concurrent vehicle

Details on study design:

On the basis of the observation of complete resorptions at dose levels of 200 mg/kg bw/d and above, an apparent increase in prenatal deaths at 25 mg/kg bw/d and above, maternal toxicity (weight loss) at 25 mg/kg bw/d, and icreased mortality of the dams at 100 mg/kg bw/d and above the dose levels for the main study were fixed.

Examinations

Maternal examinations:

Rabbits were weighed on gd 0 as well as daily on days 6 - 19 and prior to euthanasia on gd 30. Dams were observed daily during treatment for clinical signs of toxicity.

Ovaries and uterine content:

Following euthanasia, maternal liver weight and gravid uterine weight were measured. Uterine contents were evaluated for the number of implantation sites, resorptions, late fetal deaths (fetuses heavier than 10 g but displaying no vital signs) and live fetuses. the uterus was stained to reveal possible early resorptions when visible evidence of pregnancy was not apparent.

Fetal examinations:

Live fetuses were weighed and examined for exrernal abnormalities followed by evaluation for visceral malformations using a fresh tissue dissection technique. Half of the fetuses were decapitated after dissection and the heads were fixed in Bouin's solution for free-hand sectioning and axmaination. All fetal carcasses were cleared and stained with Alcian blue/Alizarin red S and examined for skeletal alterations.

Statistics:

Analyses were carried out using the general linear model procedure in the SAS software library (SAS Institute, Inc. 1985). Prior to analysis, an arcsine-square root transformation was performed on all litter-derived percentage data. Dose-response relationships for selected measures were evaluated using a test for linear trend. Analysis if variance (ANOVA) tests were used to determine whether significant dose effects, replicate effects, or dose x replicate interactions had occured. When ANOVA revealed significant differences among groups, then William's multiples comparison test and Dunnett's test were used to compare treated groups to the vehicle control group. Nominal scale measures analyzed by a test for linear trend on proportions and a chi square test for independence among treatment groups. When chi square revealed significant (p<0.05) differences among groups, then a one-tailed Fisher's exact probability test was used for pairwise comparisons between each Diglyme treated group and the vehicle control group.

Indices:

no data

Historical control data:

no data

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical signs were limited to a decreased fecal output at the high dose level.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

There was an increase in treatment-related maternal mortality at the highest dose level ( 15 vs. 4% in controls).

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

There was a loss of weight during the days of chemical treatment at dose levels of 50 mg/kg bw/d and above, with the difference from control statistically significant at each of these dose levels.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not specified

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

A decrease in weight of the gravid uterus was observed that was statistically significant at the two highest dose levels (100 and 175 mg/kg bw/d). The body weight gain, corrected for gravid uterine weight, did not differ from that of the control group in any of the dose groups.

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

effects observed, treatment-related

Description (incidence and severity):

From 75 to 100% of the bred females in the various groups were pregnant.

Maternal developmental toxicity

Number of abortions:

not examined

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

effects observed, treatment-related

Description (incidence and severity):

Significant increase in prenatal mortality at the two highest dose levels (100 and 175 mg/kg bw/d). This loss was due largely to the total resorption of 2 of 21 litters at 100 mg/kg bw/d and 5 of 17 litters at 175 mg/kg bw/d.

Early or late resorptions:

not specified

Dead fetuses:

effects observed, treatment-related

Description (incidence and severity):

There was a significant increase in prenatal mortality at the two highest dose levels (100 and 175 mg/kg bw/d). This loss was due largely to the total resorption of 2 of 21 litters at 100 mg/kg bw/d and 5 of 17 litters at 175 mg/kg bw/d.

Changes in pregnancy duration:

not examined

Changes in number of pregnant:

not examined

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

There was a significant decreasing trend in fetal body weight but no group mean was significantly different from that of the controls. There was no evidence of a sex difference in either of these parameters - live fetuses/litter of fetal body weight.

Reduction in number of live offspring:

not examined

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Anogenital distance of all rodent fetuses:

not examined

Changes in postnatal survival:

not examined

External malformations:

not specified

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

Significantly increased malformations at 100 and 175 mg/kg bw/d.
Most prevalent malformations were fused ribs in 17% (13/77) in high dose fetuses.

Visceral malformations:

effects observed, treatment-related

Description (incidence and severity):

Significantly increased malformations at 100 and 175 mg/kg bw/d. Most prevalent malformations were hydronephosis in 23% (18/77) of high-dose fetuses.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

The percentage of adversely affected (includes resorptions, late fetal death and malformed fetuses) implants/litter was significantly increased above control at dose levels of 50 mg/kg bw/d and above.
In contrast, female pups tended to have more malformations than males, with percentage of malformed fetuses per litter being significantly increased at both 100 and 175 mg/kg bw/d among female pups and only at the highest dose level among males.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

25 mg/kg bw/day

Basis for effect level:

other: adverse effects on prenatal growth, viability and morphological development

Fetal abnormalities

Abnormalities:

effects observed, treatment-related

Localisation:

skeletal: rib

other: hydronephosis, clubbing of the fore- and hindlimbs

Overall developmental toxicity

Developmental effects observed:

yes

Lowest effective dose / conc.:

25 mg/kg bw/day

Treatment related:

yes

Relation to maternal toxicity:

developmental effects in the absence of maternal toxicity effects

Applicant's summary and conclusion

Conclusions:

Exposure of New Zealand white rabbits to Diethylene glycol dimethyl ether at 25 mg/kg bw/d during gd 6 through 19 produced no adverse developmental effects. Doses of 50 mg/kg bw/d and above were associated with resorptions, late fetal death and malformed fetuses. The NOAEL (maternal) is considered to be 50 mg/kg bw/d.

Executive summary:

Diethylene glycol dimethyl ether (0, 25, 50, 100, or 175 mg/kg bw/d) were administered by gavage in distilled water to timed-pregnant New Zealand white rabbits (15 -25 dams/group) during gd 6 -19. Treated females were euthanized on gd 30, uterine contents were examined, and live fetuses were examined for morphological alterations. Evidence of maternal toxicity, per se, was observed only at 175 mg/kg bw/d with 15% mortality among treated females compared to 4% among controls. No significant maternal toxicity was observed in the 25 mg/kg bw/d group, and only minimal maternal toxicity (decreased maternal weight gain during treatment) was observed at 50 and 100 mg/kg bw/d compared to vehicle group.The NOAEL (developmental) was 25 mg/kg bw/d, the NOAEL (maternal) 50 mg/kg bw/d. The incidences of prenatal mortality and malformed live fetuses were significantly above controls at 100 and 175 mg/kg bw/d. Malformations observed most frequently included fusion of ribs to each other and hydronephrosis; clubbing of the limbs without underlying bone deformities, a variation, was also observed.