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Repeated dose toxicity: dermal

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Administrative data

Endpoint:
sub-chronic toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02 August 1990 to 14 November 1990
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: A GLP study performed to sound scientific principles with a sufficient level of detail to assess the reliability of the quality of the submitted data.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report date:
1990

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
2-phenoxyethyl isobutyrate
EC Number:
203-127-1
EC Name:
2-phenoxyethyl isobutyrate
Cas Number:
103-60-6
Molecular formula:
C12H16O3
IUPAC Name:
2-phenoxyethyl 2-methylpropanoate
Test material form:
other: liquid (undefined)
Details on test material:
- Name of test material (as cited in study report): 2-phenoxyethyl isobutyrate
- Physical state: Colourless liquid.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Age at study initiation: 4 weeks on arrival.
- Weight at study initiation: Approximate weights on arrival; males 85 g and females 60 g.
- Housing: Individually housed in suspended polypropylene cages.
- Diet: Commercial rat and mouse food, ad libitum.
- Water: Tap water, ad libitum.
- Acclimation period: 11 days.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ± 2 ºC
- Humidity (%): 55 ± 10%
- Air changes (per hr): 15 air changes per hour.
- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light.

IN-LIFE DATES: From 02 August 1990 to 14 November 1990.

Administration / exposure

Type of coverage:
occlusive
Vehicle:
other: diethyl phalate
Details on exposure:
TEST SITE
- Area of exposure: An area on the back of each animal was used as the exposure area.
- % coverage: 10% of the total body surface area.
- Type of wrap if used: An occlusive dressing consisting of a gauze patch covered by a foil backing, held in place by means of non-irritating tape
- Time intervals for shavings or clipplings: Twice weekly.

REMOVAL OF TEST SUBSTANCE
- Washing: The exposure site was cleaned of test material with diethyl phthalate immediately after removal of the dressing.
- Time after start of exposure: 6 hours

TEST MATERIAL
- Amounts applied: The test material was applied daily at 2 mL/kg.
- Concentration: 0, 100, 300 and 1000 mg/kg bw/day
- Constant volume used: yes

VEHICLE
- Amount applied: 2 mL/kg.

USE OF RESTRAINERS FOR PREVENTING INGESTION: no.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analyses of dosing solutions were undertaken with regard to accuracy of concentration of test material. The analyses were undertaken on samples of each dosing solution prepared during the first day of dosing and week 13 of the study. Analysis was also performed showing stability of the dosing solutions over a period of 14 days.
Duration of treatment / exposure:
13 weeks with a daily exposure time of 6 hours.
Frequency of treatment:
Daily.
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 100, 300 and 1000 mg/kg bw/day
Basis:

No. of animals per sex per dose:
12 animals per sex per dose.
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Dose levels were selected based on results obtained from preliminary studies where it was shown that the test material elicited erythema and desquamation, epidermal thickening hyperkeratosis and/or localised parakeratosis when applied to rats at a dose level of 1000 mg/kg bw/day.

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Viability was checked once each morning and once as late as practicable each day. Furthermore, all animals were examined for reactions to treatment during the day. The onset, intensity and duration of all signs were recorded.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals received a detailed clinical examination for evidence of systemic toxicity once each week.

DERMAL IRRITATION: Yes
- Time schedule for examinations: Twice each day (before administration and after the exposure period) the skin at the test site was inspected and assessed for reaction to treatment. Erythema, eschar, edema formation were scored according to the Draize scale. Skin thickening and desquamation were also noted.

BODY WEIGHT: Yes
- Time schedule for examinations: The weight of each animal was recorded once during the week before the start of treatment and once each week thereafter.

FOOD CONSUMPTION: Yes
- The quantity of food consumed by each animal was recorded once during the week before the start of treatment and once each week thereafter.

WATER CONSUMPTION: Yes
- Time schedule for examinations: Water consumption was monitored by visual inspection throughout the treatment period.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Week 13
- Anaesthetic used for blood collection: Yes (light ether).
- How many animals: 10 males and 10 females.
- Parameters checked in Table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Week 13
- How many animals: 10 males and 10 females
- Parameters checked in Table 2 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: Samples were collected over a 4 hour period of food and water deprivation.
- Parameters checked in Table 3 were examined.
Sacrifice and pathology:
GROSS PATHOLOGY/ HISTOPATHOLOGY: Yes
- All animals were sacrificed and necropsied after 13 weeks dosing. Method of killing was carbon dioxide asphyxiation followed by exsanguination.
- The following organs were weighed from all animals: adrenals, brain, heart, kidneys, liver, ovaries (with fallopian tubes), pituitary, testes (plus epididymides), thyroids.
- The following tissues from all animals were examined in situ and fixed: adrenals, aortic arch, any abnormal tissue, bladder, bone (sternum and rib), brain, ears, eyes, femur, heart, intestine (duodenum, jejunum, ileum, caecum, colon, rectum), kidneys, liver, lungs (perfused), mammary gland, thyroids, tongue, mesentric lymph node, muscle (thigh), nasal cavity, oesophagus, optic nerve, ovaries (with fallopian tubes), pancreas, pituitary, prostate, sciatic nerve, seminal vesicles, skin (normal and treated), spleen, stomach (glandular and non-glandular), spinal chord (thoracic-lumbar), submaxillary salivary gland, submandibular lymph node, testes (plus epididymides), thymus, trachea, uterus.
- Samples of the above tissues were taken from all animals and placed in 10% neutral buffered formalin (except eyes which were preserved in Davidson's fluid). The lungs were fixed in their entirety by perfusion with 10% neutral buffered formalin.
- Tissues were trimmed to a maximum thickness of 3 mm for processing. Parenchymal organs were trimmed to allow the largest surface area for examination.
- Multiple sections of the kidney were prepared with mid-transverse sections through the cortex and medulla of each being submitted for examination.
- Three cross sections of the brain were included; frontal cortex and basal ganglia, parietal cortex and thalamus, and the cerebellum and medulla oblongata. Tissues were cut into 4-6 µm thickness and stained with haematoxylin and eosin.
- All fixed tissues (with the exception of spinal chord, rectum, sternum, rib, muscle, ears, eyes, optic nerve, trachea, tongue, femur and nasal cavity) were processed and examined histologically from all animals in the Control Group and the High Dose Group. Kidneys were examined histologically from all animals from all dose groups.
Statistics:
Haematology, clinical chemistry, organ weight and body weight data were statistically analysed for homogeneity of variance using the F-max test. If the group variances appeared homogenous a parametric ANOVA was used and pairwise comparisons made via Student's t-test using Fisher's F-protected LSD. If the variances were heterogeneous log or square root transformations were used in an attempt to stabilise the variances. If the variances remained heterogeneous, then a non-parametric test such as Kruskal-Wallis ANOVA was used. Organ weights were also analysed conditional on body weight (i.e. covariance and relative analyses). Histology data were analysed using Fisher's Exact Probability test.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
No treatment related effects.
Dermal irritation:
effects observed, treatment-related
Description (incidence and severity):
Slight desquamation and erythema noted in all animals and the control.
Mortality:
no mortality observed
Description (incidence):
No treatment related effects.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No treatment related effects.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
No treatment related effects.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
no effects observed
Description (incidence and severity):
No treatment related effects.
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Description (incidence and severity):
No treatment related effects.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
No treatment related effects.
Urinalysis findings:
no effects observed
Description (incidence and severity):
No treatment related effects.
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
No treatment related effects.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No treatment related effects.
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
No treatment related effects.
Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
No treatment related effects.
Details on results:
CLINICAL SIGNS AND MORTALITY: No deaths were observed during the course of the study. There were no clinical signs of toxicity observed which were considered to be related to treatment with the test material.

DERMAL IRRITATION: There were transient incidences of slight desquamation and erythema, observed at similar incidence and severity, and noted in all animals, with the exception of one female control.

BODY WEIGHT AND WEIGHT GAIN: Although there were slight variations evident in body weight gain they were within normal variability and did not show any relationship to dose level. There were no statistically significant differences in body weight during the dosing period.

FOOD CONSUMPTION: Although there were slight intergroup differences in the total food consumed these differences did not show any relationship to dose level and were within normal variability.

WATER CONSUMPTION: There were no visual intergroup differences.

HAEMATOLOGY: There were no notable intergroup differences.

CLINICAL CHEMISTRY: There were no notable intergroup differences between the males. For females there was a slight reduction in potassium in the 300 mg/kg bw/day dose group (10%, P<0.05). Due to the magnitude of this change and the absence of a similar change at the higher dose level it is not considered to be related to treatment with test material.

URINALYSIS: There were no notable intergroup differences.

ORGAN WEIGHTS: There were no notable intergroup differences between the males. After correction for final body weight in females, (covariance analysis and after relative analyses) there was a slight decrease evident in ovaries weight in the 1000 mg/kg bw/day dose group (15%, P<0.05). This decrease in ovary weight was not reflected in any histological changes it is considered that this change is a chance

GROSS PATHOLOGY: Findings were infrequent and showed no notable intergroup differences.

HISTOPATHOLOGY NON-NEOPLASTIC: There were no notable intergroup differences. At the treatment site a very mild/minimal epidermal thickening with or without slight hyperkeratosis was present in all animals with the exception of one female in the control group. This reaction was also seen in the adjacent dorsal skin in a few animals in some groups. All other findings were typical of the usual background pathology seen in rats of this age and strain at the testing facility.

HISTOPATHOLOGY NEOPLASTIC: There were no notable intergroup differences. Necrotising papillitis (unilateral) was seen in the kidney of one male animal in the 100 mg/kg bw/day dose group but was not accompanied by pelvic dilatation. The changes seen in the kidneys of this animal, urothelial hyperplasia and papillitis, are similar to the changes which have been recorded or might be expected in the early stages of pyelone-phritis induced by urinary stasis and/or the introduction of bacterial infection into the ureters. It is possible that stasis could have arisen in this study due to the pressure exerted on the abdominal contents by the dressing used to hold the patch in place. Partial obstruction of the ureters could have permitted bacteria which are normally present in the urinary tract to spread up the ureters and cause inflammation in the papilla. It is therefore concluded that there are enough published results to show that the papillary lesion seen in this study could have been caused by repeated, partial obstruction of the ureters by the dressing used to hold the patch in place. It is not possible, however, to state that this was the definite cause.

Effect levels

Dose descriptor:
NOEL
Effect level:
> 1 000 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed.

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Under the conditions of the test, no treatment related effects or systemic signs of toxicity were observed during the study. Slight desquamation and erythema were observed in all animals, female ovary weights were slightly lower at 1000 mg/kg bw/day, necrotising papillitis was observed in one male treated at 100 mg/kg bw/day. Since no other notable adverse effects were observed to support these findings, these effects were considered to be of no toxicological relevance.

Accordingly the NOEL is considered to be greater than the highest concentration tested, 1000 mg/kg bw/day.
Executive summary:

The subchronic dermal toxicity of the test material was investigated following a procedure in line with that noted in the standardised guideline OECD 411. During the study groups of 12 male and 12 female rats were dosed daily with test material via topical application under an occlusive dressing, for a period of 6 hours per day for 13 consecutive weeks. The groups were dosed at a constant volume of 2 mL/kg bw at concentrations of 100, 300 and 1000 mg/kg bw/day in diethyl phalate. A vehicle control was run concurrently for comparison.

Under the conditions of the study there were no notable intergroup differences or toxicologically significant effects noted when assessing changes in; body weight, food consumption, water consumption, haematology, clinical chemistry, urinalysis, organ weights, necropsy findings or histological findings. Transient incidences of slight desquamation and erythema were observed, in all animals at similar incidence and severity.

Overall, exposing rats to the test material for 13 weeks with at dose levels of up to 1000 mg/kg bw/day produced no notable findings. The NOEL was therefore taken to be > 1000 mg/kg bw/day.