1,2-dimethoxyethane

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 March - 14 October 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well performed guideline study with minor restrictions in reporting.

Justification for type of information:

As described in 7.1, the toxic metabolite of diethylene glycol dimethyl ether is 2-methoxy ethanol. This scientifically allows the evaluation of diethylene glycol dimethyl ether toxicity based on the respective active metabolite. This metabolite was investigated within the here described study.

Cross-reference

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

23 March - 14 October 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well performed guideline study with minor restrictions in reporting.

Justification for type of information:

As described in 7.1, the toxic metabolite of diethylene glycol dimethyl ether is 2-methoxy ethanol. This scientifically allows the evaluation of diethylene glycol dimethyl ether toxicity based on the respective active metabolite. This metabolite was investigated within the here described study.

Reason / purpose for cross-reference:

assessment report

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms (Germantown, NY)
- Age at study initiation: 5-7 weeks
- Weight at study initiation: males: 24.2-24.7 g females: 20.3-21.5 g
- Housing: individually in polycarbonate cages lined with heat-treated hardwood chips and covered with polyester fiber cage top filters
- Diet (e.g. ad libitum): NIH-07 open Formula Pellets ad libitum
- Water (e.g. ad libitum): drinking water solution of 2-Methoxyethanol at target doses ad libitum
- Acclimation period: 1-2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 15.6-25°C
- Humidity (%): 20-70%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 23.03.1988 To: 14.10.1988

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

Dose formulations were prepared by mixing the appropriate amount of 2-Methoxyethanol with deionized water to achieve the desired concentrations. Dose formulations were prepared as needed and used within 3 weeks of preparation.
For the 2-week study target doses were established based on published data on the acute and short-term toxicity of 2-Methoxyethanol. Drinking water solutions of the test item were formulated at concentrations estimated to deliver the target doses. These concentrations were changed during the second week to account for changes in drinking water consumption and weight gain.
Stability studies showed that doses of 20,000 ppm 2-Methoxyethanol were stable for up to 3 weeks when stored in the dark at 5°C. 2-Methoxyethanol dosed water stored in rodent drinking bottles was also found to be stable for at least 4 days. Dose formulations were stored in the dark at 4 +/- 3°C.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Identity and purity analyses were conducted on 2-Methoxyethanol at Midwest Research Institute (MRI; MO, USA).
The following analytical methods were used:
- infrared, ultraviolet/visible spectroscopy
- nuclear magnetic resonance spectroscopy
- elemental analysis
- potentiometric titration
- functional group titration
- gas chromatography
Results of all dose formulation analyses were within 10% of theoretical concentrations.

Duration of treatment / exposure:

Study a: 2 weeks continuously
Study b: 13 weeks continuously

Frequency of treatment:

continuously; drinking water study

Dose / conc.:

200 mg/L drinking water

Remarks:

study a, m: 181 mg/kg bw/d, f: 255 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

400 mg/L drinking water

Remarks:

study a, m: 380 mg/kg bw/d, f: 544 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

600 mg/L drinking water

Remarks:

study a, m: 603 mg/kg bw/d, f: 971 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

1 000 mg/L drinking water

Remarks:

study a, m: 865 mg/kg bw/d, f: 1094 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

1 200 mg/L drinking water

Remarks:

study a, m: 1269 mg/kg bw/d, f: mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

2 000 ppm

Remarks:

study b, m: 295 mg/kg bw/d, f: 492 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

4 000 ppm

Remarks:

study b, m: 529 mg/kg bw/d, f: 902 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

6 000 ppm

Remarks:

study b, m: 765 mg/kg bw/d, f: 1194 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

8 000 ppm

Remarks:

study b, m: 992 mg/kg bw/d, f: 1489 mg/kg bw/d compound consumption based on water consumption

Dose / conc.:

10 000 ppm

Remarks:

study b, m: 1367 mg/kg bw/d, f: 1839 mg/kg bw/d compound consumption based on water consumption

No. of animals per sex per dose:

Study a: 5
Study b: 10

Control animals:

yes, concurrent vehicle

Details on study design:

Study a:
In the 2-week study groups of 5 mice per sex and dose level were administered 2-Methoxyethanol in drinking water available ad libitum. Doses were chosen due to literature data obtained from acute and subacute studies. Animals were observed twice daily and were weighed at the start, at the end of week 1 and at necropsy. Water consumption by cage was measured two times per week. Complete necropsies and histopathologic examination on those organs showing evidence of lesions were performed on all animals at study termination.

Study b:
In the 13-week study groups of 10 mice per sex and dose level were administered 2-Methoxyethanol in drinking water available ad libitum. Dosages are based on the results of the 2-week study. Animals were observed for mortality and clinical signs. Urinalysis, haematology, clinical biochemistry and examination of sperm morphology/vaginal cytology were performed. Animals were weighed weekly. Water consumption by cage was measured two times per week. Complete necropsies and histopathologic examination were performed on all animals at study termination.

Positive control:

None

Observations and examinations performed and frequency:

Study a:
- clinical signs: twice daily
- water consumption: twice weekly
- body weight: weekly

Study b:
- clinical signs: twice daily
- water consumption: twice weekly
- body weight: weekly
- haematology: days 5 and 21, week 13
- clinical biochemistry: days 5 and 21, week 13
- sperm morphology: at necropsy
- vaginal cytology: determination of estrus cycle

Sacrifice and pathology:

Study a:
- complete necropsy of all animals
- microscopical examination of organs showing gross lesions

Study b:
- complete necropsy of all animals
- microscopical examination of all tissues of control animals and animals in the highest dose group with at least 60% survivors and all animals in the higher dose groups

Other examinations:

no data

Statistics:

Analysis of continuous variables:
parametric multiple comparisons procedures of Williams or Dunnett, nonparametric multiple comparisons methods of Shirley or Dunn, Jonckheer's test, ourlier test of Dixon and Massey
Analysis of vaginal cytology data:
multivariate analysis of Variance (Morrison)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Study a:
The only clinical observation for male mice treated with 2-methoxyethanol was dehydration in 2 of 5 males in the 1200 mg/kg bw group. Dehydration was also noted in one female each in the 0, 1000, and 1200 mg/kg bw groups and in two females in the 600 mg/kg bw group.

Study b:
No clinical signs observed.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The mean body weight gains of male mice receiving 10000 ppm (study b) and female mice receiving 8000 or 10000 ppm (study b) were notably lower than those of the control group.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

effects observed, treatment-related

Description (incidence and severity):

Average water consumption decreased for all males and females treated with 200, 400, 1000 and 1200 mg/kg bw/d (study a).

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Endocrine findings:

not examined

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Study a:

Changes in organ weights were minimal. For male mice, absolute and relative testis and thymus weights decreased in a dose-related fashion, and for female mice in the two highest dose groups, absolute and relative thymus weights were lower than those of the control group.

Study b:

With exception of decreases in thymus and testis weights, most changes in absolute and relative organ weights could be attributed to low final mean body weights. Dose-related decreases were noted for the absolute and relative testis weights of male mice (4000 ppm and above) and the absolute and relative thymus weights of male and female mice (8000 ppm and above).

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Study a:
No gross lesions were found in male or female mice in study a; microscopic evaluation of tissues was not performed.

Study b:
Chemical-related gross lesions were identified in the testis and thymus. Testes from mice in the 6000, 8000 and 10000 ppm groups were small. Thymuses of males in the 8000 and 10000 ppm groups and females in the 10000 ppm group were also smaller than those of the control group animals.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Study b:

In male mice, degeneration of the testis was characterised microscopically by a dose-related, minimal to marked degeneration of the germinal epithelium in seminiferous tubules; at the higher doses, the lumen of many tubules contained only Sertoli cells. In the thymus of most males from the two highest dose groups and females in the high-dose group, there was minimal to mild lymphoid depletion (atrophy) consisting of a reduction in the thickness of the thymic cortex and in the number of thymocytes. Histopathologic changes were also present in the spleen of male (4000 ppm and above) and female mice (2000 ppm and above) and in the adrenal gland of female mice (2000 ppm and above). Increased hematopoesis was present in the spleen of mice from all dosed groups, excluding male mice in the lowest dose group (2000 ppm), and was characterised by a marked increase in the number of megakaryocytes present in the red pulp. In adrenal gland of female mice in all dosed groups, there was hypertrophy of the X-zone. In dosed mice, there was a marked increase in the lipid vacuolization normally present in this region of the adrenal gland in young female mice.

Histopathological findings: neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Study b:

Sperm morphology evaluations were performed on male mice treated with 0, 2000, 4000 or 6000 ppm 2-Methoxyethanol. Vaginal cytology evaluations were performed on female mice treated with 0, 6000, 8000 or 10000 ppm. Results showed significant decreases in epididymal and cauda epididymal weights for males in the 6000 ppm group and in testicular weight for males in the 4000 and 6000 ppm groups. The values for sperm motility were significantly less than controls for 2000 ppm and 6000 ppm groups, as were sperm concentration measurements for males treated with 2000 to 6000 ppm. Spermatid measurements were significantly lower than controls for males receiving 4000 or 6000 ppm. For females, all dose groups differed significantly from controls in the relative frequency of time spent in estrous stages.

Dose descriptor:

NOAEL

Effect level:

200 mg/L drinking water

Sex:

male

Basis for effect level:

other: reduction of relative testis weight (2 weeks drinking water study)

Dose descriptor:

NOAEL

Effect level:

600 mg/L drinking water

Sex:

female

Basis for effect level:

other: reduced relative thymus weight (2 weeks drinking water study)

Dose descriptor:

NOAEL

Effect level:

< 2 000 ppm

Sex:

male/female

Basis for effect level:

other: reduced sperm motility and concentration in males and histopathologacal changes in the spleen and adrenal gland incl. increases hematopoesis in female mice (13 weeks drinking water study)

Critical effects observed:

not specified

No data

Conclusions:

The daily intake of 200 to 1200 mg/kg bw/d 2-Methoxyethanol over a 2 week period via drinking water led to significantly reduced relative testis weights in male mice at 400 mg/kg bw/d and reduced relative thymus weights in female mice at 1000 mg/kg bw/d. Therefore, the NOAEL (2 weeks, males) is considered to be 200 mg/kg bw/d and the NOAEL (2 weeks, females) 600 mg/kg bw/d.
The daily intake of 2,000 to 10,000 ppm 2-Methoxyethanol over a 13 weeks period via drinking resulted in reduced sperm motility and concentrations in male mice and histological changes in the spleen and adrenal gland in female mice at all dosages. The NOAEL is considered to be lower than 2000 ppm.

Executive summary:

There is a strong evidence in literature that Diethyleneglycoldimethylether is metabolised to 2-Methoxyethanol . Therefore, a read across to the 2 and 13-week drinking water study with 2 -Methoxyethanol in mice was conducted.

The animals were treated with 0, 200, 400, 600, 1000 or 1200 mg/kg bw/d 2 -Methoxyethanol for 2 weeks or with 0, 200, 4000, 6000, 8000 or 10000 ppm 2 -Methoxyethanol for 13 weeks via drinking water. All animals survied.

 

2 weeks study:

The final mean body weight and mean body weight gain did not differ from those of the control group. Average water consumption decreased for all males and females treated with 200, 400, 1000 and 1200 mg/kg bw/d. The only clincal observation noted in male mice was dehydration in 2 of 5 males in the 1200 mg/kg bw/d group. Dehydration was also noted in one female each in the 0, 1000 and 1200 mg/kg bw/d groups and in 2 females in the 600 mg/kg bw/d group. Changes in organ weights were minimal. For male mice, absolute and relative testis and thymus weights decreased in a dose-related fashion, and for female mice in the two highest dose groups, absolute and relative thymus weights were lower than those of the control group. No chemical-related gross lesions were noted in male or female mice.

 

13 weeks study:

The mean body weight gains of male mice receiving 10000 ppm and female mice receiving 8000 or 10000 ppm were notably lower than those of the control group. There were no significant clinical observations in male or female mice during the study. With exception of decreases in thymus and testis weights, most changes in absolute and relative organ weights could be attributed to low final mean body weights. Dose-related decreases were noted for the absolute and relative testis weights of male mice (4000 ppm and above) and the absolute and relative thymus weights of male and female mice (8000 ppm and above). Chemical-related gross lesions were identified in the testis and thymus. Testes from mice in the 6000, 8000 and 10000 ppm groups were small. Thymuses of males in the 8000 and 10000 ppm groups and females in the 10000 ppm group were also smaller than those of the control group animals. In male mice, degeneration of the testis was characterised microscopically by a dose-related, minimal to marked degeneration of the germinal epithelium in seminiferous tubules; at the higher doses, the lumen of many tubules contained only Sertoli cells. In the thymus of most males from the two highest dose groups and females in the high-dose group, there was minimal to mild lymphoid depletion (atrophy) consisting of a reduction in the thickness of the thymic cortex and in the number of thymocytes. Histopathologic changes were also present in the spleen of male (4000 ppm and above) and female mice (2000 ppm and above) and in the adrenal gland of female mice (2000 ppm and above). Increased hematopoesis was present in the spleen of mice from all dosed groups, excluding male mice in the lowest dose group (2000 ppm), and was characterised by a marked increase in the number of megakaryocytes present in the red pulp. In adrenal gland of female mice in all dosed groups, there was hypertrophy of the X-zone. In dosed mice, there was a marked increase in the lipid vacuolization normally present in this region of the adrenal gland in young female mice. Sperm morphology evaluations were performed on male mice treated with 0, 2000, 4000 or 6000 ppm 2-Methoxyethanol. Vaginal cytology evaluations were performed on female mice treated with 0, 6000, 8000 or 10000 ppm. Results showed significant decreases in epididymal and cauda epididymal weights for males in the 6000 ppm group and in testicular weight for males in the 4000 and 6000 ppm groups. The values for sperm motility were significantly less than controls for 2000 ppm and 6000 ppm groups, as were sperm concentration measurements for males treated with 2000 to 6000 ppm. Spermatid measurements were significantly lower than controls for males receiving 4000 or 6000 ppm. For females, all dose groups differed significantly from controls in the relative frequency of time spent in estrous stages.

 

In summary, the major target organs for toxicity were testes in males and the hematopoetic system in both sexes. 2 -Methoxyethanol appeared primarily to act primarily as a spermatotoxic and immunotoxic agent.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1993

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-methoxyethanol

EC Number:

203-713-7

EC Name:

2-methoxyethanol

Cas Number:

109-86-4

Molecular formula:

C3H8O2

IUPAC Name:

2-methoxyethanol

Constituent 2

Reference substance name:

203-86-4

IUPAC Name:

203-86-4

Details on test material:

- Name of test material (as cited in study report): 2-Methoxyethanol
- Molecular formula (if other than submission substance): C3H8O2
obtained from Kodak Laboratory Chemicales (NY, USA)
Lot: E16
Puritiy: 98%

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms (Germantown, NY)
- Age at study initiation: 5-7 weeks
- Weight at study initiation: males: 24.2-24.7 g females: 20.3-21.5 g
- Housing: individually in polycarbonate cages lined with heat-treated hardwood chips and covered with polyester fiber cage top filters
- Diet (e.g. ad libitum): NIH-07 open Formula Pellets ad libitum
- Water (e.g. ad libitum): drinking water solution of 2-Methoxyethanol at target doses ad libitum
- Acclimation period: 1-2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 15.6-25°C
- Humidity (%): 20-70%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 23.03.1988 To: 14.10.1988

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

Dose formulations were prepared by mixing the appropriate amount of 2-Methoxyethanol with deionized water to achieve the desired concentrations. Dose formulations were prepared as needed and used within 3 weeks of preparation.
For the 2-week study target doses were established based on published data on the acute and short-term toxicity of 2-Methoxyethanol. Drinking water solutions of the test item were formulated at concentrations estimated to deliver the target doses. These concentrations were changed during the second week to account for changes in drinking water consumption and weight gain.
Stability studies showed that doses of 20,000 ppm 2-Methoxyethanol were stable for up to 3 weeks when stored in the dark at 5°C. 2-Methoxyethanol dosed water stored in rodent drinking bottles was also found to be stable for at least 4 days. Dose formulations were stored in the dark at 4 +/- 3°C.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Identity and purity analyses were conducted on 2-Methoxyethanol at Midwest Research Institute (MRI; MO, USA).
The following analytical methods were used:
- infrared, ultraviolet/visible spectroscopy
- nuclear magnetic resonance spectroscopy
- elemental analysis
- potentiometric titration
- functional group titration
- gas chromatography
Results of all dose formulation analyses were within 10% of theoretical concentrations.

Duration of treatment / exposure:

Study a: 2 weeks continuously
Study b: 13 weeks continuously

Frequency of treatment:

continuously; drinking water study

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

200 mg/L drinking water

Remarks:

study a, m: 181 mg/kg bw/d, f: 255 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 2

Dose / conc.:

400 mg/L drinking water

Remarks:

study a, m: 380 mg/kg bw/d, f: 544 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 3

Dose / conc.:

600 mg/L drinking water

Remarks:

study a, m: 603 mg/kg bw/d, f: 971 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 4

Dose / conc.:

1 000 mg/L drinking water

Remarks:

study a, m: 865 mg/kg bw/d, f: 1094 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 5

Dose / conc.:

1 200 mg/L drinking water

Remarks:

study a, m: 1269 mg/kg bw/d, f: mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 6

Dose / conc.:

2 000 ppm

Remarks:

study b, m: 295 mg/kg bw/d, f: 492 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 7

Dose / conc.:

4 000 ppm

Remarks:

study b, m: 529 mg/kg bw/d, f: 902 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 8

Dose / conc.:

6 000 ppm

Remarks:

study b, m: 765 mg/kg bw/d, f: 1194 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 9

Dose / conc.:

8 000 ppm

Remarks:

study b, m: 992 mg/kg bw/d, f: 1489 mg/kg bw/d compound consumption based on water consumption

Doses / concentrations 10

Dose / conc.:

10 000 ppm

Remarks:

study b, m: 1367 mg/kg bw/d, f: 1839 mg/kg bw/d compound consumption based on water consumption

No. of animals per sex per dose:

Study a: 5
Study b: 10

Control animals:

yes, concurrent vehicle

Details on study design:

Study a:
In the 2-week study groups of 5 mice per sex and dose level were administered 2-Methoxyethanol in drinking water available ad libitum. Doses were chosen due to literature data obtained from acute and subacute studies. Animals were observed twice daily and were weighed at the start, at the end of week 1 and at necropsy. Water consumption by cage was measured two times per week. Complete necropsies and histopathologic examination on those organs showing evidence of lesions were performed on all animals at study termination.

Study b:
In the 13-week study groups of 10 mice per sex and dose level were administered 2-Methoxyethanol in drinking water available ad libitum. Dosages are based on the results of the 2-week study. Animals were observed for mortality and clinical signs. Urinalysis, haematology, clinical biochemistry and examination of sperm morphology/vaginal cytology were performed. Animals were weighed weekly. Water consumption by cage was measured two times per week. Complete necropsies and histopathologic examination were performed on all animals at study termination.

Positive control:

None

Examinations

Observations and examinations performed and frequency:

Study a:
- clinical signs: twice daily
- water consumption: twice weekly
- body weight: weekly

Study b:
- clinical signs: twice daily
- water consumption: twice weekly
- body weight: weekly
- haematology: days 5 and 21, week 13
- clinical biochemistry: days 5 and 21, week 13
- sperm morphology: at necropsy
- vaginal cytology: determination of estrus cycle

Sacrifice and pathology:

Study a:
- complete necropsy of all animals
- microscopical examination of organs showing gross lesions

Study b:
- complete necropsy of all animals
- microscopical examination of all tissues of control animals and animals in the highest dose group with at least 60% survivors and all animals in the higher dose groups

Other examinations:

no data

Statistics:

Analysis of continuous variables:
parametric multiple comparisons procedures of Williams or Dunnett, nonparametric multiple comparisons methods of Shirley or Dunn, Jonckheer's test, ourlier test of Dixon and Massey
Analysis of vaginal cytology data:
multivariate analysis of Variance (Morrison)

Results and discussion

Results of examinations

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Study a:
The only clinical observation for male mice treated with 2-methoxyethanol was dehydration in 2 of 5 males in the 1200 mg/kg bw group. Dehydration was also noted in one female each in the 0, 1000, and 1200 mg/kg bw groups and in two females in the 600 mg/kg bw group.

Study b:
No clinical signs observed.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The mean body weight gains of male mice receiving 10000 ppm (study b) and female mice receiving 8000 or 10000 ppm (study b) were notably lower than those of the control group.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

effects observed, treatment-related

Description (incidence and severity):

Average water consumption decreased for all males and females treated with 200, 400, 1000 and 1200 mg/kg bw/d (study a).

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Endocrine findings:

not examined

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Study a:

Changes in organ weights were minimal. For male mice, absolute and relative testis and thymus weights decreased in a dose-related fashion, and for female mice in the two highest dose groups, absolute and relative thymus weights were lower than those of the control group.

Study b:

With exception of decreases in thymus and testis weights, most changes in absolute and relative organ weights could be attributed to low final mean body weights. Dose-related decreases were noted for the absolute and relative testis weights of male mice (4000 ppm and above) and the absolute and relative thymus weights of male and female mice (8000 ppm and above).

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Study a:
No gross lesions were found in male or female mice in study a; microscopic evaluation of tissues was not performed.

Study b:
Chemical-related gross lesions were identified in the testis and thymus. Testes from mice in the 6000, 8000 and 10000 ppm groups were small. Thymuses of males in the 8000 and 10000 ppm groups and females in the 10000 ppm group were also smaller than those of the control group animals.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Study b:

In male mice, degeneration of the testis was characterised microscopically by a dose-related, minimal to marked degeneration of the germinal epithelium in seminiferous tubules; at the higher doses, the lumen of many tubules contained only Sertoli cells. In the thymus of most males from the two highest dose groups and females in the high-dose group, there was minimal to mild lymphoid depletion (atrophy) consisting of a reduction in the thickness of the thymic cortex and in the number of thymocytes. Histopathologic changes were also present in the spleen of male (4000 ppm and above) and female mice (2000 ppm and above) and in the adrenal gland of female mice (2000 ppm and above). Increased hematopoesis was present in the spleen of mice from all dosed groups, excluding male mice in the lowest dose group (2000 ppm), and was characterised by a marked increase in the number of megakaryocytes present in the red pulp. In adrenal gland of female mice in all dosed groups, there was hypertrophy of the X-zone. In dosed mice, there was a marked increase in the lipid vacuolization normally present in this region of the adrenal gland in young female mice.

Histopathological findings: neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Study b:

Sperm morphology evaluations were performed on male mice treated with 0, 2000, 4000 or 6000 ppm 2-Methoxyethanol. Vaginal cytology evaluations were performed on female mice treated with 0, 6000, 8000 or 10000 ppm. Results showed significant decreases in epididymal and cauda epididymal weights for males in the 6000 ppm group and in testicular weight for males in the 4000 and 6000 ppm groups. The values for sperm motility were significantly less than controls for 2000 ppm and 6000 ppm groups, as were sperm concentration measurements for males treated with 2000 to 6000 ppm. Spermatid measurements were significantly lower than controls for males receiving 4000 or 6000 ppm. For females, all dose groups differed significantly from controls in the relative frequency of time spent in estrous stages.

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

200 mg/L drinking water

Sex:

male

Basis for effect level:

other: reduction of relative testis weight (2 weeks drinking water study)

2

Dose descriptor:

NOAEL

Effect level:

600 mg/L drinking water

Sex:

female

Basis for effect level:

other: reduced relative thymus weight (2 weeks drinking water study)

3

Dose descriptor:

NOAEL

Effect level:

< 2 000 ppm

Sex:

male/female

Basis for effect level:

other: reduced sperm motility and concentration in males and histopathologacal changes in the spleen and adrenal gland incl. increases hematopoesis in female mice (13 weeks drinking water study)

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

No data

Applicant's summary and conclusion

Conclusions:

The daily intake of 200 to 1200 mg/kg bw/d 2-Methoxyethanol over a 2 week period via drinking water led to significantly reduced relative testis weights in male mice at 400 mg/kg bw/d and reduced relative thymus weights in female mice at 1000 mg/kg bw/d. Therefore, the NOAEL (2 weeks, males) is considered to be 200 mg/kg bw/d and the NOAEL (2 weeks, females) 600 mg/kg bw/d.
The daily intake of 2,000 to 10,000 ppm 2-Methoxyethanol over a 13 weeks period via drinking resulted in reduced sperm motility and concentrations in male mice and histological changes in the spleen and adrenal gland in female mice at all dosages. The NOAEL is considered to be lower than 2000 ppm.

Executive summary:

There is a strong evidence in literature that Diethyleneglycoldimethylether is metabolised to 2-Methoxyethanol . Therefore, a read across to the 2 and 13-week drinking water study with 2 -Methoxyethanol in mice was conducted.

The animals were treated with 0, 200, 400, 600, 1000 or 1200 mg/kg bw/d 2 -Methoxyethanol for 2 weeks or with 0, 200, 4000, 6000, 8000 or 10000 ppm 2 -Methoxyethanol for 13 weeks via drinking water. All animals survied.

 

2 weeks study:

The final mean body weight and mean body weight gain did not differ from those of the control group. Average water consumption decreased for all males and females treated with 200, 400, 1000 and 1200 mg/kg bw/d. The only clincal observation noted in male mice was dehydration in 2 of 5 males in the 1200 mg/kg bw/d group. Dehydration was also noted in one female each in the 0, 1000 and 1200 mg/kg bw/d groups and in 2 females in the 600 mg/kg bw/d group. Changes in organ weights were minimal. For male mice, absolute and relative testis and thymus weights decreased in a dose-related fashion, and for female mice in the two highest dose groups, absolute and relative thymus weights were lower than those of the control group. No chemical-related gross lesions were noted in male or female mice.

 

13 weeks study:

The mean body weight gains of male mice receiving 10000 ppm and female mice receiving 8000 or 10000 ppm were notably lower than those of the control group. There were no significant clinical observations in male or female mice during the study. With exception of decreases in thymus and testis weights, most changes in absolute and relative organ weights could be attributed to low final mean body weights. Dose-related decreases were noted for the absolute and relative testis weights of male mice (4000 ppm and above) and the absolute and relative thymus weights of male and female mice (8000 ppm and above). Chemical-related gross lesions were identified in the testis and thymus. Testes from mice in the 6000, 8000 and 10000 ppm groups were small. Thymuses of males in the 8000 and 10000 ppm groups and females in the 10000 ppm group were also smaller than those of the control group animals. In male mice, degeneration of the testis was characterised microscopically by a dose-related, minimal to marked degeneration of the germinal epithelium in seminiferous tubules; at the higher doses, the lumen of many tubules contained only Sertoli cells. In the thymus of most males from the two highest dose groups and females in the high-dose group, there was minimal to mild lymphoid depletion (atrophy) consisting of a reduction in the thickness of the thymic cortex and in the number of thymocytes. Histopathologic changes were also present in the spleen of male (4000 ppm and above) and female mice (2000 ppm and above) and in the adrenal gland of female mice (2000 ppm and above). Increased hematopoesis was present in the spleen of mice from all dosed groups, excluding male mice in the lowest dose group (2000 ppm), and was characterised by a marked increase in the number of megakaryocytes present in the red pulp. In adrenal gland of female mice in all dosed groups, there was hypertrophy of the X-zone. In dosed mice, there was a marked increase in the lipid vacuolization normally present in this region of the adrenal gland in young female mice. Sperm morphology evaluations were performed on male mice treated with 0, 2000, 4000 or 6000 ppm 2-Methoxyethanol. Vaginal cytology evaluations were performed on female mice treated with 0, 6000, 8000 or 10000 ppm. Results showed significant decreases in epididymal and cauda epididymal weights for males in the 6000 ppm group and in testicular weight for males in the 4000 and 6000 ppm groups. The values for sperm motility were significantly less than controls for 2000 ppm and 6000 ppm groups, as were sperm concentration measurements for males treated with 2000 to 6000 ppm. Spermatid measurements were significantly lower than controls for males receiving 4000 or 6000 ppm. For females, all dose groups differed significantly from controls in the relative frequency of time spent in estrous stages.

 

In summary, the major target organs for toxicity were testes in males and the hematopoetic system in both sexes. 2 -Methoxyethanol appeared primarily to act primarily as a spermatotoxic and immunotoxic agent.