Registration Dossier

Administrative data

Description of key information

For the oral route, a 28-day oral gavage study conducted under GLP and according to guideline (KANPOGYO No.700, YAKUHATSU No. 1039.61, and KIKYKU No. 1014) is available for dipropylene glycol methyl ether. For the dermal route two non-GLP studies equivalent to OECD guidelines 410 (in rats) and 411 (in rabbits) are available for dipropylene glycol methyl ether. For the inhalation route, GLP-studies in rats and rabbits according to OECD guideline 413 and 412 are available for dipropylene glycol methyl ether. In addition, several non-GLP studies in rats, rabbits, guinea pigs and monkeys, similar to OECD guideline 452 were conducted with dipropylene glycol methyl ether.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
other: KANPOGYO No.700, YAKUHATSU No. 1039.61, and KIKYKU No. 1014.
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
Source: Charles River Japan Inc.
- Age at study initiation: 6-7 weeks
- Weight at study initiation: Male: 208 to 235 gms and Female: 140 to 169 gms
- Fasting period before study:
- Housing:
- Diet (ad libitum): A pelleted laboratory rodent diet autoclaved CRF-1
- Water (ad libitum): Tap water irradiated with the ultraviolet light
- Acclimation period: 10 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 23 °C
- Humidity (%): 30-70%
- Air changes (per hr): 20
- Photoperiod: (12 hrs dark /12 hrs light):


IN-LIFE DATES: From: 2000-01-11 To: 2000-05-10
Route of administration:
oral: gavage
Vehicle:
other: Water for injection
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: Test substance was diluted with water for injection to 0.4 %, 2 % and 10 % concentration which were equivalent to the 40, 200 and 1000 mg/kg respectively. Formulation was prepared freshly each day
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
Not specified in the report
Duration of treatment / exposure:
4 weeks
Frequency of treatment:
daily
Remarks:
Doses / Concentrations:
40 mg/kg
Basis:
nominal in water
Remarks:
Doses / Concentrations:
200, mg/kg
Basis:
nominal in water
Remarks:
Doses / Concentrations:
1000 mg/kg
Basis:
nominal in water
No. of animals per sex per dose:
5/sex/dose
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: 2 weeks (controls and high dose)
Positive control:
None
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed three times daily (immediately before and after administration and 1 to 2 hour after administration later from the treatment) for clinical signs.

BODY WEIGHT: Yes
- Time schedule for examinations: All the rats were weighed on the first day of administration, twice a week during treatment and recovery period, on the day before necropsy and on the day of necropsy.


FOOD CONSUMPTION: Food consumption of all rats were measured weekly for 2 days and daily food intakes were calculated.
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

FOOD EFFICIENCY: Not examined
WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No
OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: During necropsy
- Anesthetic used for blood collection: Yes (identity) : Ether
- Animals fasted: No
- How many animals: 20 male and 20 female for regular dose levels and 10 male +10 female for recovery group
- Parameters checked in table [No.5-1 and 5-2] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: During necropsy
- Animals fasted: No
- How many animals: 20 male and 20 female for regular dose levels and 10 male +10 female for recovery group
- Parameters checked in table [No.6-1 and 6-2] were examined.


URINALYSIS: Yes
- Time schedule for collection of urine: During 4th week of administration and 2nd week of recovery period.
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes
- Parameters checked in table [No.4-1, 4-2, 4-3, 4-4] were examined.


NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All surviving animals were fasted from the evening at the end of treatment period or at the end of recovery period. On the next day animals were examined by bleeding from the abdominal aorta under anesthesia for necropsy and the organs and tissues were macroscopically.
HISTOPATHOLOGY: Yes
As to the autopsied animals, eyes (Including optic nerve) were preserved in Davidson's fixative and following tissues were preserved in 10 % buffered formalin. Brain, pituitary, thyroids, heart, thymus, trachea and lung (fulfilled with the fixative), liver, spleen, esophagus, stomach, duodenum, ileum, colon, kidneys, adrenals, urinary bladder, testes, epididymides, prostrate, ovaries, uterus, femoral bone, spinal cord, sciatic nerve and lymph nodes.
Other examinations:
Organ weights: The following organs from each animal autopsied were dissected and weighed. Relative organ weight to body weight was calculated. Brain, heart, thymus, liver, kidneys, spleen, adrenals, testes, epididymides and ovaries.
Statistics:
As to quantative data the Bartlett’s test was applied to test for heterogeneity of variance between treatments. If no significant heterogeneity was detected, a one way analysis of variance was carried out. If significant heterogeneity was detected then analysis was followed by Dunnet to compare the control and treatments. If significant hetrogeneity of variance was present, the Krushkal -Wallis analysis of ranks was used. Statistical analysis was performed on two sides tests at 5 % and 1 % level of significance.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY: All animals were survived during the treatment period of 28 days and 2 weeks of recovery period. Salivation was noted immediately after daily treatment in the 9 male and 3 female animals treated with the 1000 mg/kg from day 11 onward. However, this sign disappeared within 1 to 2 hours from the treatment and it seems to be a temporal change. There were sporadic incidence of soft stool, muddy stool but there was no difference of incidence between the groups. There was no change in all animals of recovery group.

BODY WEIGHT AND WEIGHT GAIN: There were no significant differences between control group and treatment groups for body weights.

FOOD CONSUMPTION: There were no significant differences between control group and treatment groups for food consumption. For recovery group in the first week there was statistically higher value was noted in the male treated with the 1000 mg/kg dose group but it disappeared in the second week.

HAEMATOLOGY: In the 28 day treatment group, MCHC were recorded statistically significant in 200 mg/kg dose level as compare to controls but there was no statistical significance in the animals treated with 1000 mg/kg dose level. The above change found in 200 mg/kg was not related to the dose levels. There were no other changes in the parameters determined.
In the recovery group statistically significant higher Ht and Hb concentrations were noted in the female animals treated with 1000 mg/kg. However, differences from the control were always small. There were no other changes in the parameters determined.

CLINICAL CHEMISTRY: In the 28 day treatment group, chloride level was statistically significantly higher than control for rats treated with 40 mg/kg and for male rats treated with 200 and 1000 mg/kg. Additionally, a statistically significantly lower Alb and Glb in ration than control was noted in female rats treated with 200 and 1000 mg/kg.There were no other changes in the parameters determined.
In recovery group statistically significantly higher glucose and total glyceride value were noted in the male animals treated with 1000 mg/kg while female animals treated with 1000 mg/kg showed statistically significantly lower Alb/Glb in ration and total bilirubin values. However, these differences from control were also small. There were no other changes in the parameters determined.

URINALYSIS: In the 28 day treatment group, there were no differences from control in urinalysis in any of the treatment groups. In recovery group statistically lower potassium value was noted in female animals treated with the 1000 mg/kg but this extent of difference was small and there were no other parameters to show the difference with those of the control.

ORGAN WEIGHTS: In the 28 day treatment group, statistically significantly higher relative liver weights were noted in the male and female animals treated with 1000 mg/kg. Absolute and relative liver weights in the groups treated with more than 200 mg/kg showed a tendency of increases in the relation with the dose levels, while animals treated with 40 mg/kg showed the similar level of liver weight as in control animals. Statistically significantly lower relative heart weight was noted for the male animals treated with 40 or 200 mg/kg but there was no significant increase in the animals treated with 1000 mg/kg and there was no dose relationship for this change. There were no other parameters to show the difference with those of the control.
In recovery group, statistically significantly higher relative liver weight was noted in the male animals treated with 1000 mg/kg. There was also the relatively higher value of liver weight for female animals at same dose group but without statistical significant. There were no other differences in the absolute and relative organ weight from control.

GROSS PATHOLOGY: Macroscopic examination performed at 28 days treatment and recovery period revealed no changes in the animals of the treatment attributable to treatment with this test substance.

HISTOPATHOLOGY: NON-NEOPLASTIC: In the 28 day treatment group, centrilobular hypertrophy was noted in the livers of two animals treated with the 1000 mg/kg but there was no change in the groups treated with less than 200 mg/kg.Slight to moderate grade of the eosinophil bodies were noted in the proximal tubules of each one male treated with 40 or 1000 mg/kg. In addition to above findings, aggregation of mononuclear cells of slight degree were noted in the liver of two control female animals and two 1000 mg/kg male animals. Slight degree of regeneration of renal tubules was noted in the one male each of control, 200 mg/kg and 1000 mg/kg animal and one slight degree of aggregation of mononuclear cells was noted in one male control animal.Extramedually hematopoiesis of spleen was noted in all animals of control and animals treated with 1000 mg/kg which was slight to moderate degree. In one male animal of the control, there was a slight degree of epithelial abruption in seminiferous tubules. Slight to moderate degree of cell infiltration of mononuclear cells in epididymides and prostate was noted in one male each of control and 1000 mg/kg group. Slight degree of aggregation of foamy cells in lung was noted in a female treated with 1000 mg/kg.

In recovery groups, slight degree of centrilobular hypertrophy in liver was noted in two male animals treated with 1000 mg/kg.Moderate to severe degree of eosinophilic bodies in proximal tubules was noted in the two male animals treated with 1000 mg/kg. Aggregation of mononeulaer cells of slight degree were noted in the liver of one control male and two control females animals and four 1000 mg/kg male animals and two 1000 mg/kg female animals. One male animal of control showed a slight degree of vacuolation and one female animal of control showed a slight degree of focal vacuolation.Slight degree of regeneration of renal tubules was noted in the one male of control and two male treated with 1000 mg/kg and one slight degree of infiltration of mononuclear cells was noted in one male animal treated with 1000 mg/kg. Extramedually hematopoiesis of spleen was noted in all animals of control and animals treated with 1000 mg/kg which was slight degree. Slight degree of infiltration of mononuclear cells in urinary bladder was noted in one male treated with 1000 mg/kg.Slight to moderate degree of infiltration of mononuclear cells in prostate was noted in the two control animals and two animals treated with 1000 mg/kg.Slight degree of aggregation of foamy cells in lung was noted in one male treated with 1000 mg/kg. Slight degree of cyst in pituitary was noted in one male treated with 1000 mg/kg.




Dose descriptor:
NOEL
Effect level:
200 other: mg/kg
Sex:
male/female
Basis for effect level:
other: overall effects
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: tentative salivation, increased relative liver weight accompanied by centrilobular hypertrophy
Critical effects observed:
not specified
The liver weight increase observed at the highest dose level was only slight and no histopathologic changes, except for hypertrophy, accompanied this effect. There were no changes in clinical chemistry (ALP, ASP) indicating a liver damage. The same effect was observed with other structurally related molecules, e.g. propylene glycol methyl ether has been shown to cause liver weight increases via a phenobarbital-like enzyme induction mode of action and it is highly likely that dipropylene glycol methyl ether acetate liver weight increases occur via the same mode of action. As this is an adaptive effect typical for many glycol ethers, it is not consered as adverse.
Conclusions:
Based on the results of this study a no observed adverse effect level (NOAEL) of 1000 mg DPM/kg-day and a no observed effect level (NOEL) of 200 mg/kg/dayc an be established in rats under the conditions of this study.
Executive summary:

This study was performed to assess the systemic toxicity of dipropylene glycol methyl ether (DPGME) to the rat by oral administration, once daily for 28 days, to 3 groups of 5 male and 5 female rats at dosage levels of 40, 200 and 1000 mg/kg/day. A negative control group was provided. A recovery group of 5 males and 5 females were additionally assigned to the control group and high dose group.

All animals survived during the treatment period of 28 days and the 2 weeks recovery period. There were no significant differences between control group and treatment groups for body weights and food consumption. Macroscopic examination performed at the end of the 28 days treatment and the recovery period revealed no treatment-related changes.

Tentative salivation was recorded in the male and female animals treated with the 1000 mg/kg from the day 11 onward, which appeared immediately after oral administration of test substance. Relative liver weight of male and female animals treated with the 1000 mg/kg at 28 days treatment increased with statistical significance, while the male animals treated with 1000 mg/kg at recovery group showed also a statistical significant increases in absolute and relative livery weight. Upon histopathological examination centrilobular hypertrophy of the liver was observed in the animals treated with 1000 mg/kg.

There were no other changes that were considered to be related to treatment of this test substance.

It is concluded that 200 mg/kg/day represents the no-observed-effect level (NOEL) and that 1000 mg/kg/day represents no-observed-adverse-effect level (NOAEL)for DPGME in the rat. The only effects observed at 1000 mg/day were transient salivation immediately after administration of the test material, increased liver weight and centrilobular hypertrophy of the liver. The liver weight increase (which was very minor, <10 %) and hypertrophy in the liver observed at 1000 mg/kg/day was likely due to increased metabolism and was not accompanied by an increase in liver enzymes.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
Good (Klimisch 1)

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study was conducted in accordance with GLP and comparable to OECD guideline 413.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Rats: Charles River Breeding Laboratories
- Age at study initiation: For rats 9 weeks approximately
- Weight at study initiation: For rat 190-200 gms approximately
- Housing: Rats 2/cage were housed in stainless steel cages with wire bottoms
- Diet: A standard laboratory diet (Purina Certified Laboratory Chow, Ralston Purina Co.) adlibitum except during exposure
- Water: Adlibitum water was supplied to rats except during exposure
- Acclimation period: 2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): Standard conditions
- Humidity (%): Standard conditions
- Air changes (per hr): Standard conditions
- Photoperiod (hrs dark / hrs light): Standard conditions
Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass inhalation chambers (4 m3 volume)
- Method of holding animals in test chamber: Whole body
- Method of conditioning air: DPGME was vaporized and metered into the chambers with a compressed air flame less heat torch/J-Tube assembly as described by Miller.
- Temperature, humidity, pressure in air chamber: Chamber temperature and relative humidity were controlled by a system designed to main 20-24Ca nd 40-60 % relative humidity
- Air flow rate: 800 l/m
- Air change rate: Not specified in the report
- Treatment of exhaust air: Not specified in the report


TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of DPGME in each chamber was measured approximately once per hour with a Varian 2400 GC with a 1/8" by 6' nickel column and flame ionization detector. Standard bags were made by adding DPGME to a U Tube 100 l of dry filtered air was metered through the tube into a gas tight bag. Heat was applied to the test material to facilitate vaporization. A series of standards, which included 15, 50, 200 ppm were made and analyzed at least biweekly to produce a standard curve.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
See the attchment-1
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
6 hours/day; 5 days/week
Remarks:
Doses / Concentrations:
15 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
50, ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
200 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
Rats: 10/sex/dose
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on the 2-week inhalation study which was conducted prior to this 13-week study
- Rationale for animal assignment (if not random): Random animal assignment
Post-exposure period: none
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice a daily
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: After each exposure

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were determined during the randomization procedure, on the first day exposure and weekly thereafter for the duration of study.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: After 12 weeks of exposure
- Anesthetic used for blood collection: Yes
- How many animals: Rats (40 male and 40 female)
- Parameters checked in table [No. 15, 16, 17, 18] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Prior to necropsy
- Animals fasted: Yes
- How many animals: (40 male and 40 female)
- Parameters checked in table [No.11, 12, 13, 14] were examined.


URINALYSIS: Yes Rats only
- Time schedule for collection of urine: After 12 weeks of exposure
- Metabolism cages used for collection of urine: No data
-- Parameters checked in table [No.19] were examined.

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All surviving animals underwent a gross necropsy on the day following their last exposure. Rats were deprived of food overnight prior to necropsy. Rats were anesthetized with methoxyflurane, and then decapitated. The trachea of all animals was clamped after anesthesia to prevent aspiration of blood during decapiatation.Each animal was examined internally and externally for gross pathological changes. The heart, liver, kidneys, brain, thymus (Rats) and testes were removed from each animal and weighed. Eyes of all animals were examined grossly using a microscope slide technique with fluorescent illumination. Representative portions of tissues were preserved in buffered 10 % formalin. Liver samples were fixed in a phosphate buffered 2% gluteraldehyde 2 % and formalin 2 % solution, then routinely processed and embedded in EPON 812 resin for possible electron microscopy examination.

HISTOPATHOLOGY: Yes
An extensive set of tissues, intended to include one or more sections of all tissues listed in table no. 1 were examined histologically from all animals in the control and high exposure groups. Gall bladder (rabbits only), nasal turbinates (rats only), liver, kidneys were also examined in the middle and low exposure groups. Tissues were processed by conventional techniques, stained with hematoxylin and eosin and evaluated by light microscopy.
Other examinations:
Organ weights: The heart, liver, kidneys, brain, thymus and testes were removed from each animal and weighed.
Statistics:
Clinical chemistry, hematology(PCV, HgB, RBC, WBC and Plat only). urinary specific gravity, organ weight, body weight and organ to body weight ratio data were evaluated by Bartlett's test for the equality of variances’ the group variances were homogenous, a parametric analysis of variances was conducted to determine if any statistically significant differences exist between groups. If the overall parametric ANOVA was significant at < 0.10, Dunnett's test was used to identify statistically significant differences between experimental groups and their corresponding control. If group variances were not homogenous, the data was evaluated by non parametric analysis of variance and if significant at p<0.1, Wilcoxon's Rank Sum test was used to identify statistically significant differences between experimental groups and their corresponding control. Outlying values for each parameter evaluated were identified, but not routinely excluded from statistical analyses. The nominal level of statistical significance, for evaluating differences between exposed and control groups was <0.05. The actual probability of erroneously rejecting the hypothesis that there are no differences between treated and control mean values.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
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:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY: There were no DPGME exposure related adverse effects on body weights in rats during the 13 week study. There were no statistically significant differences from control body weight means in male and female rats.

BODY WEIGHT AND WEIGHT GAIN: There were no DPGME exposure related adverse effects on body weights in rats during the 13 week study. There were no statistically significant differences from control body weight means in male and female rats.

HAEMATOLOGY: There were no exposure related effects on any of the measured hematology parameters in either sex of rat. There were also no statistically significant differences from control means.

CLINICAL CHEMISTRY: There were no exposure related effects on any of the measured clinical chemistry parameters in either sex of rat. The only statistically significant difference was a slight decrease in BUN in female rats exposed to 50 ppm, this had no toxicological significance.

URINALYSIS: There were no apparent effects on any of the urinalysis parameters of male and female rats.

ORGAN WEIGHTS: There were also no statistically significant differences in absolute or relative organ weights of rats exposed to DPGME, except for a slight decrease in mean relative liver weight of 50 ppm exposed males.

GROSS PATHOLOGY AND HISTOPATHOLOGY: All gross and histopathologic observations were considered to be spontaneous changes of minimal severity which were not treatment related. Based on gross observations, liver from rats exposed to DPGME appeared to be increased in size, however this observation was not supported by group mean liver weights and there was no histopathologic evidence of hepatocellular swelling.


Dose descriptor:
NOAEL
Effect level:
200 ppm
Sex:
male/female
Basis for effect level:
other: overall effects
Critical effects observed:
not specified
Conclusions:
Based on the results of this study the NOAEL for dipropylene glycol methyl ether for inhalation exposure of Fischer-344 rats is 200 ppm.
Executive summary:

Fischer-344 rats (10/sex/exposure) were exposed to 0, 15, 50 and 200 ppm (0, 91, 303 and 1212 mg/m3) of dipropylene glycol monomethyl ether (DPGME) for 6 hr/day, 5 days /week for 13 weeks.

There were no DPGME exposure related adverse effects on body weights in rats during the 13 week study. There were no statistically significant differences from control body weight means in male and female rats. There were no exposure related effects on any of the measured hematology parameters in either sex of rat. There were also no statistically significant differences from control means. There were no exposure related effects on any of the measured clinical chemistry parameters in either sex of rat. The only statistically significant difference was a slight decrease in BUN in female rats exposed to 50 ppm, but this had no toxicological significance. There were no apparent effects on any of the urinalysis parameters of male and female rats. There were also no statistically significant differences in absolute or relative organ weights of rats exposed to DPGME, except for a slight decrease in mean relative liver weight of 50 ppm exposed males.

All gross and histopathologic observations were considered to be spontaneous changes of minimal severity which were not treatment related. Based on gross observations, liver from rats exposed to DPGME appeared to be increased in size, however this observation was not supported by group mean liver weights and there was no histopathologic evidence of hepatocellular swelling.

Based on the results of this study the NOAEL for dipropylene glycol methyl ether for inhalation exposure of Fischer-344 rats is 200 ppm.

 

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
1 232 mg/m³
Study duration:
subchronic
Species:
rat
Quality of whole database:
Good (Klimisch 2)

Repeated dose toxicity: inhalation - local effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study was conducted in accordance with GLP and comparable to OECD guideline 413.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Rats: Charles River Breeding Laboratories
- Age at study initiation: For rats 9 weeks approximately
- Weight at study initiation: For rat 190-200 gms approximately
- Housing: Rats 2/cage were housed in stainless steel cages with wire bottoms
- Diet: A standard laboratory diet (Purina Certified Laboratory Chow, Ralston Purina Co.) adlibitum except during exposure
- Water: Adlibitum water was supplied to rats except during exposure
- Acclimation period: 2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): Standard conditions
- Humidity (%): Standard conditions
- Air changes (per hr): Standard conditions
- Photoperiod (hrs dark / hrs light): Standard conditions
Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass inhalation chambers (4 m3 volume)
- Method of holding animals in test chamber: Whole body
- Method of conditioning air: DPGME was vaporized and metered into the chambers with a compressed air flame less heat torch/J-Tube assembly as described by Miller.
- Temperature, humidity, pressure in air chamber: Chamber temperature and relative humidity were controlled by a system designed to main 20-24Ca nd 40-60 % relative humidity
- Air flow rate: 800 l/m
- Air change rate: Not specified in the report
- Treatment of exhaust air: Not specified in the report


TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of DPGME in each chamber was measured approximately once per hour with a Varian 2400 GC with a 1/8" by 6' nickel column and flame ionization detector. Standard bags were made by adding DPGME to a U Tube 100 l of dry filtered air was metered through the tube into a gas tight bag. Heat was applied to the test material to facilitate vaporization. A series of standards, which included 15, 50, 200 ppm were made and analyzed at least biweekly to produce a standard curve.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
See the attchment-1
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
6 hours/day; 5 days/week
Remarks:
Doses / Concentrations:
15 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
50, ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
200 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
Rats: 10/sex/dose
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on the 2-week inhalation study which was conducted prior to this 13-week study
- Rationale for animal assignment (if not random): Random animal assignment
Post-exposure period: none
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice a daily
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: After each exposure

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were determined during the randomization procedure, on the first day exposure and weekly thereafter for the duration of study.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: After 12 weeks of exposure
- Anesthetic used for blood collection: Yes
- How many animals: Rats (40 male and 40 female)
- Parameters checked in table [No. 15, 16, 17, 18] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Prior to necropsy
- Animals fasted: Yes
- How many animals: (40 male and 40 female)
- Parameters checked in table [No.11, 12, 13, 14] were examined.


URINALYSIS: Yes Rats only
- Time schedule for collection of urine: After 12 weeks of exposure
- Metabolism cages used for collection of urine: No data
-- Parameters checked in table [No.19] were examined.

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All surviving animals underwent a gross necropsy on the day following their last exposure. Rats were deprived of food overnight prior to necropsy. Rats were anesthetized with methoxyflurane, and then decapitated. The trachea of all animals was clamped after anesthesia to prevent aspiration of blood during decapiatation.Each animal was examined internally and externally for gross pathological changes. The heart, liver, kidneys, brain, thymus (Rats) and testes were removed from each animal and weighed. Eyes of all animals were examined grossly using a microscope slide technique with fluorescent illumination. Representative portions of tissues were preserved in buffered 10 % formalin. Liver samples were fixed in a phosphate buffered 2% gluteraldehyde 2 % and formalin 2 % solution, then routinely processed and embedded in EPON 812 resin for possible electron microscopy examination.

HISTOPATHOLOGY: Yes
An extensive set of tissues, intended to include one or more sections of all tissues listed in table no. 1 were examined histologically from all animals in the control and high exposure groups. Gall bladder (rabbits only), nasal turbinates (rats only), liver, kidneys were also examined in the middle and low exposure groups. Tissues were processed by conventional techniques, stained with hematoxylin and eosin and evaluated by light microscopy.
Other examinations:
Organ weights: The heart, liver, kidneys, brain, thymus and testes were removed from each animal and weighed.
Statistics:
Clinical chemistry, hematology(PCV, HgB, RBC, WBC and Plat only). urinary specific gravity, organ weight, body weight and organ to body weight ratio data were evaluated by Bartlett's test for the equality of variances’ the group variances were homogenous, a parametric analysis of variances was conducted to determine if any statistically significant differences exist between groups. If the overall parametric ANOVA was significant at < 0.10, Dunnett's test was used to identify statistically significant differences between experimental groups and their corresponding control. If group variances were not homogenous, the data was evaluated by non parametric analysis of variance and if significant at p<0.1, Wilcoxon's Rank Sum test was used to identify statistically significant differences between experimental groups and their corresponding control. Outlying values for each parameter evaluated were identified, but not routinely excluded from statistical analyses. The nominal level of statistical significance, for evaluating differences between exposed and control groups was <0.05. The actual probability of erroneously rejecting the hypothesis that there are no differences between treated and control mean values.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
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:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY: There were no DPGME exposure related adverse effects on body weights in rats during the 13 week study. There were no statistically significant differences from control body weight means in male and female rats.

BODY WEIGHT AND WEIGHT GAIN: There were no DPGME exposure related adverse effects on body weights in rats during the 13 week study. There were no statistically significant differences from control body weight means in male and female rats.

HAEMATOLOGY: There were no exposure related effects on any of the measured hematology parameters in either sex of rat. There were also no statistically significant differences from control means.

CLINICAL CHEMISTRY: There were no exposure related effects on any of the measured clinical chemistry parameters in either sex of rat. The only statistically significant difference was a slight decrease in BUN in female rats exposed to 50 ppm, this had no toxicological significance.

URINALYSIS: There were no apparent effects on any of the urinalysis parameters of male and female rats.

ORGAN WEIGHTS: There were also no statistically significant differences in absolute or relative organ weights of rats exposed to DPGME, except for a slight decrease in mean relative liver weight of 50 ppm exposed males.

GROSS PATHOLOGY AND HISTOPATHOLOGY: All gross and histopathologic observations were considered to be spontaneous changes of minimal severity which were not treatment related. Based on gross observations, liver from rats exposed to DPGME appeared to be increased in size, however this observation was not supported by group mean liver weights and there was no histopathologic evidence of hepatocellular swelling.


Dose descriptor:
NOAEL
Effect level:
200 ppm
Sex:
male/female
Basis for effect level:
other: overall effects
Critical effects observed:
not specified
Conclusions:
Based on the results of this study the NOAEL for dipropylene glycol methyl ether for inhalation exposure of Fischer-344 rats is 200 ppm.
Executive summary:

Fischer-344 rats (10/sex/exposure) were exposed to 0, 15, 50 and 200 ppm (0, 91, 303 and 1212 mg/m3) of dipropylene glycol monomethyl ether (DPGME) for 6 hr/day, 5 days /week for 13 weeks.

There were no DPGME exposure related adverse effects on body weights in rats during the 13 week study. There were no statistically significant differences from control body weight means in male and female rats. There were no exposure related effects on any of the measured hematology parameters in either sex of rat. There were also no statistically significant differences from control means. There were no exposure related effects on any of the measured clinical chemistry parameters in either sex of rat. The only statistically significant difference was a slight decrease in BUN in female rats exposed to 50 ppm, but this had no toxicological significance. There were no apparent effects on any of the urinalysis parameters of male and female rats. There were also no statistically significant differences in absolute or relative organ weights of rats exposed to DPGME, except for a slight decrease in mean relative liver weight of 50 ppm exposed males.

All gross and histopathologic observations were considered to be spontaneous changes of minimal severity which were not treatment related. Based on gross observations, liver from rats exposed to DPGME appeared to be increased in size, however this observation was not supported by group mean liver weights and there was no histopathologic evidence of hepatocellular swelling.

Based on the results of this study the NOAEL for dipropylene glycol methyl ether for inhalation exposure of Fischer-344 rats is 200 ppm.

 

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
1 232 mg/m³
Study duration:
subchronic
Species:
rat
Quality of whole database:
Good (Klimisch 2)

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1950
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study was conducted prior to GLP and test guidelines, but sufficient data is available for interpretation of results.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day Study)
GLP compliance:
no
Limit test:
no
Species:
rabbit
Strain:
not specified
Sex:
male
Type of coverage:
occlusive
Vehicle:
water
Details on exposure:
Route of Administration: dermal
Analytical verification of doses or concentrations:
no
Duration of treatment / exposure:
90 days
Frequency of treatment:
5 days/week
Remarks:
Doses / Concentrations:
1 ml/kg
Basis:

Remarks:
Doses / Concentrations:
3 ml/kg
Basis:

Remarks:
Doses / Concentrations:
5 ml/kg
Basis:

Remarks:
Doses / Concentrations:
10 ml/kg
Basis:

No. of animals per sex per dose:
Only male rabbits were used. Total no. of animals used: 29 rabbits
Control group-5
1 ml/kg-5
3 ml/kg-6
5 ml/kg-6
10 ml/kg-7
Control animals:
yes
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes

DERMAL IRRITATION (if dermal study): Yes

BODY WEIGHT: Yes
- Time schedule for examinations: Rabbits were weighed before the application of each daily dose of the test compound.

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

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Control blood counts were taken before the start of the study and on the thirtieth and ninetieth day of the application of the compound.
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 29 animals before the start of the study, 30th day-22 and 90th day-20 animals
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Statistics:
Possible significance between means was studied by students test of "t".
Clinical signs:
effects observed, treatment-related
Dermal irritation:
no effects observed
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
Dowanol 50B at the 10 ml/kg and 5 ml/kg produced some narcosis. However narcosis was not observed at lower dose levels (1.0 and 3.0 ml/kg).
Mortality was high at the 10.0 ml/kg dosage level, slight at 5.0 ml/kg, low at 3.0 ml/kg(1/6) and absent at the 1.0 ml/kg dose level.
BODY WEIGHT AND WEIGHT GAIN
No adverse body weight changes occurred at any level except just prior to death in those animals that succumbed, presumably to the narcotic effects of the top dosage levels.


HAEMATOLOGY
No haematological changes, occurred at any dosage level.


ORGAN WEIGHTS
No significant organ weight changes occurred at any dosage level.

GROSS PATHOLOGY
Observations for gross pathology revealed only gastric distension and occasional gastric irritation in those animals dying at the 10 ml/kg dosage level.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological studies conducted on the liver, lung, spleen, adrenal, heart, testes and stomach of those animals receiving the 5.0 and 10.0 ml/kg dosage levels revealed no changes. The kidneys of those animals on the 10.0 ml/kg level showed some granular and some hydropic changes, at the 5.0 ml/kg same kidney abnormalities were observed but they were of no greater intensity than those observed in some of the controls.


OTHER FINDINGS
The effect of severe (repeated and prolonged) exposure to the skin was slight, being similar to that caused by distilled water under similar conditions. No skin irritation was observed during 90 days of exposure.
Dose descriptor:
NOAEL
Effect level:
2 850 mg/kg bw/day (actual dose received)
Sex:
male/female
Critical effects observed:
not specified
Conclusions:
The NOEL for dipropylene glycol methyl ether in rabbits following dermal exposure was 2850 mg/kg bw/day under the conditions of this study.
Executive summary:

DOWANOL 50B, the methyl ether of dipropylene glycol, a colorless liquid was evaluated for chronic skin absorption in rabbits.

 

Male rabbits were selected and divided into groups of at least five animals each. Dipropylene glycol methyl ether was applied over the abdominal skin using the following technique. A pad of absorbent cotton about 3”×3” in size and sufficiently thick just to absorb the volume of the test material was applied to the clipped abdomen of the rabbit. The proper dose of the compound was added to the cotton and the pad was then covered with an impervious saran film about 5”×5”. This saran film was covered with a heavy cloth, and the whole application was then strapped onto the animal with adhesive tape. Dipropylene glycol methyl ether was thus applied five times a week over a period of three months at four dosage levels: 1.0, 3.0, 5.0 and 10.0 ml/kg. A separate group of five animals to which distilled water was bandaged served as controls.

 

The rabbits received the stock diet of commercial rabbit chow and water ad libitum. The rabbits were weighed before the application of each daily dose of the test compound. Control blood counts were taken before the start of the study and on the thirtieth and ninetieth day of the application of the compound. Possible significance between means was studied by students test of “t”. On the ninetieth day the rabbits were autopsied and tissues taken from the liver, kidneys, spleen, adrenal, heart, lung and occasionally stomach, for histopathological examination. Such sections were stained with haematoxylin and eosin.

 

Dipropylene glycol methyl ether at the 10 ml/kg and 5 ml/kg produced some narcosis. However narcosis was not observed at lower dose levels (1.0 and 3.0 ml/kg). Mortality was high at the 10.0 ml/kg dosage level, slight at 5.0 ml/kg and absent at the 1.0 and 3.0 ml/kg dose levels.

 

No adverse body weight changes occurred at any level except just prior to death in those animals that succumbed, presumably to the narcotic effects of the top dosage levels.

 

No haematological changes occurred at any dosage level. No significant organ weight changes occurred at any dosage level. Observations for gross pathology revealed only gastric distension and occasional gastric irritation in those animals dying at the 10 ml/kg dosage level.

 

Histopathological studies conducted on the liver, lung, spleen, adrenal, heart, testes and stomach of those animals receiving the 5.0 and 10.0 ml/kg dosage levels revealed no changes. The kidneys of those animals on the 10.0 ml/kg level showed some granular and some hydropic changes, at the 5.0 ml/kg same kidney abnormalities were observed but they were of no greater intensity than those observed in some of the controls.

 

The effect of severe (repeated and prolonged) exposure to the skin was slight, being similar to that caused by distilled water under similar conditions.                                            

                                           

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
2 850 mg/kg bw/day
Study duration:
subchronic
Species:
rabbit
Quality of whole database:
Good (Klimisch 2)

Repeated dose toxicity: dermal - local effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1950
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study was conducted prior to GLP and test guidelines, but sufficient data is available for interpretation of results.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day Study)
GLP compliance:
no
Limit test:
no
Species:
rabbit
Strain:
not specified
Sex:
male
Type of coverage:
occlusive
Vehicle:
water
Details on exposure:
Route of Administration: dermal
Analytical verification of doses or concentrations:
no
Duration of treatment / exposure:
90 days
Frequency of treatment:
5 days/week
Remarks:
Doses / Concentrations:
1 ml/kg
Basis:

Remarks:
Doses / Concentrations:
3 ml/kg
Basis:

Remarks:
Doses / Concentrations:
5 ml/kg
Basis:

Remarks:
Doses / Concentrations:
10 ml/kg
Basis:

No. of animals per sex per dose:
Only male rabbits were used. Total no. of animals used: 29 rabbits
Control group-5
1 ml/kg-5
3 ml/kg-6
5 ml/kg-6
10 ml/kg-7
Control animals:
yes
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes

DERMAL IRRITATION (if dermal study): Yes

BODY WEIGHT: Yes
- Time schedule for examinations: Rabbits were weighed before the application of each daily dose of the test compound.

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

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Control blood counts were taken before the start of the study and on the thirtieth and ninetieth day of the application of the compound.
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 29 animals before the start of the study, 30th day-22 and 90th day-20 animals
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Statistics:
Possible significance between means was studied by students test of "t".
Clinical signs:
effects observed, treatment-related
Dermal irritation:
no effects observed
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
Dowanol 50B at the 10 ml/kg and 5 ml/kg produced some narcosis. However narcosis was not observed at lower dose levels (1.0 and 3.0 ml/kg).
Mortality was high at the 10.0 ml/kg dosage level, slight at 5.0 ml/kg, low at 3.0 ml/kg(1/6) and absent at the 1.0 ml/kg dose level.
BODY WEIGHT AND WEIGHT GAIN
No adverse body weight changes occurred at any level except just prior to death in those animals that succumbed, presumably to the narcotic effects of the top dosage levels.


HAEMATOLOGY
No haematological changes, occurred at any dosage level.


ORGAN WEIGHTS
No significant organ weight changes occurred at any dosage level.

GROSS PATHOLOGY
Observations for gross pathology revealed only gastric distension and occasional gastric irritation in those animals dying at the 10 ml/kg dosage level.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological studies conducted on the liver, lung, spleen, adrenal, heart, testes and stomach of those animals receiving the 5.0 and 10.0 ml/kg dosage levels revealed no changes. The kidneys of those animals on the 10.0 ml/kg level showed some granular and some hydropic changes, at the 5.0 ml/kg same kidney abnormalities were observed but they were of no greater intensity than those observed in some of the controls.


OTHER FINDINGS
The effect of severe (repeated and prolonged) exposure to the skin was slight, being similar to that caused by distilled water under similar conditions. No skin irritation was observed during 90 days of exposure.
Dose descriptor:
NOAEL
Effect level:
2 850 mg/kg bw/day (actual dose received)
Sex:
male/female
Critical effects observed:
not specified
Conclusions:
The NOEL for dipropylene glycol methyl ether in rabbits following dermal exposure was 2850 mg/kg bw/day under the conditions of this study.
Executive summary:

DOWANOL 50B, the methyl ether of dipropylene glycol, a colorless liquid was evaluated for chronic skin absorption in rabbits.

 

Male rabbits were selected and divided into groups of at least five animals each. Dipropylene glycol methyl ether was applied over the abdominal skin using the following technique. A pad of absorbent cotton about 3”×3” in size and sufficiently thick just to absorb the volume of the test material was applied to the clipped abdomen of the rabbit. The proper dose of the compound was added to the cotton and the pad was then covered with an impervious saran film about 5”×5”. This saran film was covered with a heavy cloth, and the whole application was then strapped onto the animal with adhesive tape. Dipropylene glycol methyl ether was thus applied five times a week over a period of three months at four dosage levels: 1.0, 3.0, 5.0 and 10.0 ml/kg. A separate group of five animals to which distilled water was bandaged served as controls.

 

The rabbits received the stock diet of commercial rabbit chow and water ad libitum. The rabbits were weighed before the application of each daily dose of the test compound. Control blood counts were taken before the start of the study and on the thirtieth and ninetieth day of the application of the compound. Possible significance between means was studied by students test of “t”. On the ninetieth day the rabbits were autopsied and tissues taken from the liver, kidneys, spleen, adrenal, heart, lung and occasionally stomach, for histopathological examination. Such sections were stained with haematoxylin and eosin.

 

Dipropylene glycol methyl ether at the 10 ml/kg and 5 ml/kg produced some narcosis. However narcosis was not observed at lower dose levels (1.0 and 3.0 ml/kg). Mortality was high at the 10.0 ml/kg dosage level, slight at 5.0 ml/kg and absent at the 1.0 and 3.0 ml/kg dose levels.

 

No adverse body weight changes occurred at any level except just prior to death in those animals that succumbed, presumably to the narcotic effects of the top dosage levels.

 

No haematological changes occurred at any dosage level. No significant organ weight changes occurred at any dosage level. Observations for gross pathology revealed only gastric distension and occasional gastric irritation in those animals dying at the 10 ml/kg dosage level.

 

Histopathological studies conducted on the liver, lung, spleen, adrenal, heart, testes and stomach of those animals receiving the 5.0 and 10.0 ml/kg dosage levels revealed no changes. The kidneys of those animals on the 10.0 ml/kg level showed some granular and some hydropic changes, at the 5.0 ml/kg same kidney abnormalities were observed but they were of no greater intensity than those observed in some of the controls.

 

The effect of severe (repeated and prolonged) exposure to the skin was slight, being similar to that caused by distilled water under similar conditions.                                            

                                           

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Study duration:
subchronic
Species:
rabbit
Quality of whole database:
Good (Klimisch 2)

Additional information

The 28-day oral gavage study in rats is of high quality and considered to be reliable without restrictions (Klimisch 1). The only effects observed during this study were salivation and increased liver weights at the highest dose level. The liver weight increase observed at the highest dose level was only slight and no histopathologic changes, except for hypertrophy, accompanied this effect. There were no changes in clinical chemistry (ALP, ASP) indicating a liver damage. The same effect was observed with other structurally related molecules, e.g. propylene glycol methyl ether has been shown to cause liver weight increases via a phenobarbital-like enzyme induction mode of action and it is highly likely that dipropylene glycol methyl ether liver weight increases occur via the same mode of action. As this is an adaptive effect typical for many glycol ethers, it is not consered as adverse. Based on the results of this study a no observed adverse effect level (NOAEL) of 1000 mg/kg bw/day and a no observed effect level (NOEL) of 200 mg/kg/day can be established in rats under the conditions of this study.

The two studies via the dermal route are both reliable with restrictions as they were not conducted under GLP, but are equivalent to OECD guidelines. No adverse effects were observed up to 1000 mg/kg bw/day in a 28 -day study in rats. In a 90-day study in rabbits dipropylene glycol methyl ether produced some narcosis at 10 ml/kg bw/day and 5 ml/kg bw/day. No narcosis was observed at lower dose levels (1.0 and 3.0 ml/kg bw/day). Mortality was high at the 10.0 ml/kg dose level, some mortality was observed at 5.0 ml/kg bw/day and no mortality was observed at the 1.0 and 3.0 ml/kg bw/day dose levels. No haematological changes occurred at any dosage level. No significant organ weight changes occurred at any dosage level. Observations for gross pathology revealed only gastric distension and occasional gastric irritation in those animals dying at the 10 ml/kg dosage level. Histopathological analysis done on the liver, lung, spleen, adrenal, heart, testes and stomach of those animals receiving the 5.0 and 10.0 ml/kg bw/day dose levels revealed no changes. The kidneys of those animals on the 10.0 ml/kg bw/day level showed some granular and some hydropic changes, at the 5.0 ml/kg same kidney abnormalities were observed but they were of no greater intensity than those observed in some of the controls. The effect of severe (repeated and prolonged) exposure to the skin was slight, being similar to that caused by distilled water under similar conditions. Based on the results of this study a NOAEL of 3.0 ml/kg bw/day (2850 mg/kg/day) was established for dermal exposure to dipropylene glycol methyl ether.

No significant adverse effects were observed in rats, rabbits, guinea pigs and monkeys after repeated inhalation exposure to dipropylene glycol methyl ether at any of the test concentrations. The 90 -day inhalation studies in rats and rabbits were selected as key studies as these studies are reliable without restrictions. The highest concentration tested in these studies were 200 ppm which was identified as the NOAEC. Based on a the molecular weight of 148, this converts to 1232 mg/m3 at 20 deg Celcius and 1 atm.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The study was conducted according to Japanese guidelines and in accordance with the Principles of GLP.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
This study was conducted in accordance with GLP and comparable to OECD guideline 413.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
This study was conducted in accordance with GLP and comparable to OECD guideline 413.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
This study was conducted prior to GLP and test guidelines, but sufficient data is available for interpretation of results.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
This study was conducted prior to GLP and test guidelines, but sufficient data is available for interpretation of results.

Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver

Repeated dose toxicity: inhalation - systemic effects (target organ) digestive: liver

Repeated dose toxicity: dermal - systemic effects (target organ) urogenital: kidneys

Justification for classification or non-classification

The no observed adverse effect levels for dipropylene glycol methyl ether exceed the values triggering classification via all routes of exposure. Therefore no classification for prolonged exposure is required.