Registration Dossier

Administrative data

Endpoint:
sub-chronic toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
May 1987-February 1988
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study according to OECD guideline 411
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1988
Report Date:
1988

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day Study)
Principles of method if other than guideline:
n/a
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Identity: Dowanol-DPnB (n-butoxypropoxypropanol or
dipropylene glycol normal-butyl ether).
CAS # 29911-28-2
Batch No.: O2
Product ID: E-3125
Purity: "more than 95%"
Supplied as: Not reported.
Appearance: Clear liquid.
Administered as: Solution in propylene glycol.
Vapor pressure: Not specified.
Specific Gravity: 0.91 kg/liter.
Solubility: Not specified.
Storage: At ambient temperature in the dark.
Stability: Stable up to 200°C.

Test animals

Species:
rat
Strain:
other: Wistar (Bor: WISW (SPF Cpb))
Sex:
male/female
Details on test animals and environmental conditions:
See details below

Administration / exposure

Type of coverage:
other: non-occluded application, covered with collars
Vehicle:
propylene glycol
Details on exposure:
Dipropylene glycol n-butyl ether (DPnB) was applied daily (5 days/week) for 13 weeks to the skin of four groups of Wistar rats (10/sex/dose level) at various dilutions in propylene glycol (PG) equivalent to doses of 0 (PG-only; 1.5 ml/kg-day), 0.1, 0.3, or 1.0 ml DPnB/kg-day.  These doses equate to 0, 91, 273, or 910 mg DPnB/kg-day.  Treatment solutions were applied to the clipped dorsal trunk of each rat.  Dilutions of DPnB in PG resulted in applied volumes of 1.5 to 2.5 ml test solution per kg body weight.  Rats wore collars to prevent grooming and ingestion of test material.  Solutions were applied unoccluded since the low vapor pressure of DPnB and PG precluded evaporative loss.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The content of DPnB was determined in the solutions prepared on 11-5-87, 22-5-87, 5-6-87 and 3-7-87. The left-overs of the test solutions prepared on 22-5-87 were reanalyzed after storage for 2 weeks under the experimental solutions. The analyses were carried out at TNO, Institute CIVO-Analysis.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
5 days/week
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 91, 273, or 910 mg/kg bw-day (0.1, 0.3, or 1 ml/kg bw-day)
Basis:
nominal per unit body weight
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
Post-exposure period: none
Positive control:
none

Examinations

Observations and examinations performed and frequency:
Rats were observed for clinical signs of toxicity and skin reactions on a daily basis (week days).  Body weights and food consumption were monitored weekly.  Ophthalmological examinations were conducted in control and high dose subjects prior to treatment and on day 85 of the study. Hematology, clinical chemistries, and urinalyses were conducted at the end of the treatment period.  
Sacrifice and pathology:
At sacrifice, all animals were subjected to complete necropsy.  An extensive list of tissues was preserved from all animals and histopathological evaluations of these tissues were conducted on control and high dose animals. 
Other examinations:
n/a
Statistics:
Data on body weights were evaluated by one-way analysis of co-variance followed by Dunnett's multiple comparison test. Data on food intake, food efficiency, red blood cell variables, total white blood cells, clinical chemistry values, volume and density of the urine, and organ weights were evaluated by one-way analysis of variance (ANOVA) followed by Dunnett's multiple comparison test. Differential white blood cell counts were analyzed by the Mann-Whiteney U-test. The results of ophthalmoscopic examination and the histopathological changes were examined by Fisher's exact probability test.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Dermal irritation:
effects observed, treatment-related
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
effects observed, treatment-related
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
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:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
Skin at the site of application showed irritation in all treatment groups including PG-controls.  Grossly, irritation appeared as erythema, edema, scaliness, incrustations, and superficial scar tissue.  Skin lesions were characterized microscopically by focal necrosis of the epidermis, crust formation, mild inflammatory changes and acanthosis.  These changes were more severe in the high DPnB-treatment group. Untreated skin was unaffected.  The authors considered skin lesions to be a direct, local effect from the solvents and the clipping procedure. One high-dose male with a palpable mass was removed from the study and later died.  Necropsy and microscopic analysis of this subject revealed an overfilled urinary bladder due to obstruction of the urinary tract.  This death was not deemed treatment-related.  

No changes were observed in clinical appearance or behavior.  

Body weights in mid and high-dose males were lower than controls from week three until the end of the study.  

Food consumption was slightly increased in high-dose females and food conversion efficiency in mid and high-dose males was lower than controls (conversion efficiency differences were not generally statistically significant).  

Ophthalmological examination showed no effect from DPnB treatment.  White cell counts (neutrophils) were increased in mid and high-dose males with a similar but lesser trend in females.  SGOT (ALT) and SGPT (AST) were increased in high-dose males and triglycerides were increased in high-dose females.  Also, glucose was decreased in high-dose females. 

Urinalyses revealed no differences between control and DPnB-treated rats.  

Relative liver weights of both sexes were elevated in the high-dose group. 

No differences were noted between treated and control subjects from gross examination at necropsy.  Histopathology revealed the changes described above in the area of skin where treatment solutions were applied.  No other microscopic lesions were attributable to DPnB treatment.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
91 other: mg/kg
Sex:
male/female
Basis for effect level:
other: body weight changes and increased neutrophil counts at 273 mg/kg-day
Dose descriptor:
LOAEL
Effect level:
273 other: mg/kg
Sex:
male/female
Basis for effect level:
other: body weight changes and increased neutrophil counts

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

none

Applicant's summary and conclusion

Conclusions:
This study established a systemic toxicity NOAEL for DPnB of 0.1 ml/kg-day, or 91 mg/kg-day. A LOAEL, based on body weight changes and increased neutrophil counts, was 0.3 ml/kg-day or 273 mg/kg-day. No evidence was found for a hemolytic effect from DPnB treatment.
Executive summary:

Dipropylene glycol n-butyl ether (DPnB) was applied daily (5 days/week) for 13 weeks to the skin of four groups of Wistar
rats (10/sex/dose level) at various dilutions in propylene glycol (PG) equivalent to doses of 0 (PG-only; 1.5
ml/kg-day), 0.1, 0.3, or 1.0 ml DPnB/kg-day.  These doses equate to 0, 91, 273, or 910 mg DPnB/kg-day.  Treatment
solutions were applied to the clipped dorsal trunk of each rat.  Dilutions of DPnB in PG resulted in applied volumes of
1.5 to 2.5 ml test solution per kg body weight.  Rats wore collars to prevent grooming and ingestion of test material. 
Solutions were applied unoccluded since the low vapor pressure of DPnB and PG precluded evaporative loss.

Rats were observed for clinical signs of toxicity and skin reactions on a daily basis (week days).  Body weights and
food consumption were monitored weekly.  Ophthalmological examinations were conducted in control and high dose
subjects prior to treatment and on day 85 of the study. Hematology, clinical chemistries, and urinalyses were conducted at the end of the treatment period.  At sacrifice, all animals were subjected to complete necropsy.  An
extensive list of tissues was preserved from all animals and histopathological evaluations of these tissues were conducted on control and high dose animals.
 

.

Skin at the site of application showed irritation in all treatment groups including PG-controls.  Grossly, irritation appeared as erythema, edema, scaliness, incrustations, and superficial scar tissue.  Skin lesions were characterized
microscopically by focal necrosis of the epidermis, crust formation, mild inflammatory changes and acanthosis.  These
changes were more severe in the high DPnB-treatment group. Untreated skin was unaffected.  The authors considered skin
lesions to be a direct, local effect from the solvents and the clipping procedure.

One high-dose male with a palpable mass was removed from the study and later died.  Necropsy and microscopic analysis of
this subject revealed an overfilled urinary bladder due to obstruction of the urinary tract.  This death was not deemed
treatment-related.  No changes were observed in clinical appearance or behavior.  Body weights in mid and high-dose
males were lower than controls from week three until the end of the study.  Food consumption was slightly increased in
high-dose females and food conversion efficiency in mid and high-dose males was lower than controls (conversion
efficiency differences were not generally statistically significant).  Ophthalmological examination showed no effect
from DPnB treatment.  White cell counts (neutrophils) were increased in mid and high-dose males with a similar but
lesser trend in females.  SGOT (ALT) and SGPT (AST) were increased in high-dose males and triglycerides were
increased in high-dose females.  Also, glucose was decreased in high-dose females.  Urinalyses revealed no differences
between control and DPnB-treated rats.  Relative liver weights of both sexes were elevated in the high-dose group. 
No differences were noted between treated and control subjects from gross examination at necropsy.  Histopathology
revealed the changes described above in the area of skin where treatment solutions were applied.  No other microscopic lesions were attributable to DPnB treatment.

Skin at the site of application showed irritation in all treatment groups including PG-controls.  Grossly, irritation appeared as erythema, edema, scaliness, incrustations, and superficial scar tissue.  Skin lesions were characterized
microscopically by focal necrosis of the epidermis, crust formation, mild inflammatory changes and acanthosis.  These
changes were more severe in the high DPnB-treatment group. Untreated skin was unaffected.  The authors considered skin
lesions to be a direct, local effect from the solvents and the clipping procedure.

This study established a systemic toxicity NOAEL for DPnB of 0.1 ml/kg-day, or 91 mg/kg-day. A LOAEL, based on body weight changes and increased neutrophil counts, was 0.3 ml/kg-day or 273 mg/kg-day. No evidence was found for a hemolytic effect from DPnB treatment.

This study was identified as key for this toxicity endpoint because of the methods followed (which were comprehensively
documented in the report).  The report included GLP and Quality Assurance statements, signed by the Study Director
and Head of the QA Unit, respectively.  The study report followed OECD Protocol 411: "Subchronic Dermal Toxicity:
90-day Study," the numbers and type of test animals used and their husbandry conditions were as prescribed in the
guidance.  Test material characterization was adequate. The amount of test material applied complied with guidance, the
length of the treatment period (90 days) was sufficient, and evaluation criteria and statistical methods were typical for
this type assay and adequately recorded.