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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
April 1979
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1986

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Principles of method if other than guideline:
Groups of 10 rats of each sex were administered DGRE in corn oil by gavage, 5 days per week for 13 weeks, at doses of O, 12.5, 25, 50,100, or 200 mg/ kg body weight.
GLP compliance:
no
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid: viscous
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Ciba-Geigy Corporation (Ardsley, NY), Araldite ERE 1359 in a single lot (No. P-60002)
- Purity test date: 81.2%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: in the dark at 23 °C in its original container
- Stability under test conditions: stable

FORM AS APPLIED IN THE TEST: suspended in corn oil (dissolved in acetone before being added to corn oil)

Test animals

Species:
rat
Strain:
Fischer 344
Remarks:
F344/N
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Portage, MI
- Age at study initiation: 8 to 9 weeks
- Weight at study initiation: NA
- Fasting period before study: NA
- Housing: five animals/cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 3 weeks

DETAILS OF FOOD AND WATER QUALITY:
Feed: Wayne Laboratory Blox (r), Allied Mills (Chicago, IL)
Water: Edstrom automatic watering system, Edstrom Industries (Waterford, WI)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17-32
- Humidity (%): 20-81
- Air changes (per hr): 12 changes of room air per hour
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
- PREPARATION OF DOSING SOLUTIONS: Corn oil was selected for the gavage vehicle and was analyzed monthly for peroxides.
A quantity of DGRE was melted by warming the chemical in a 40°C water bath and a 2.5 g portion of the clear liquefied chemical was transferred to a 200 mL centrifuge bottle and mixed with 44.2g of corn oil. No acetone was used. The mixture was homogenized using a Brinkman Polytron(R) homogenizer set at low speed for 1 minute. Air bubbles incorporated in the suspension during homogenization were removed by drawing a vacuum on the bottle with an aspirator while agitating the contents periodically for 2-3 minutes. The resulting mixture was visually homogeneous and appeared to remain stable for up to 2 hours. This combination of chemical and corn oil produced 50.0 mL of suspension containing DGRE at a concentration of 50.0 mg/mL.

Maximum storage time: 10 days
Storage conditions: 5 °C

- VEHICLE
- Concentration in vehicle: 4, 8.3, 16.7 mg/mL
- Amount of vehicle: 3 mL/kg
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
One-milliliter aliquots of the sample vials were extracted with 10 mL of methanol containing 0.7 g/mL of dibutyl phthalate as an internal standard. A reference calibration plot was prepared from spiked samples which were extracted in the same manner. The supernatant solutions were analyzed by VPC-FID at 210° on a 6 ft x 1/4 in x 2 mm ID glass column packed with SP2250 on 100/120 Supelcoport.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
5 days per week
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
first study
Dose / conc.:
12.5 mg/kg bw/day (actual dose received)
Dose / conc.:
25 mg/kg bw/day (actual dose received)
Remarks:
first study
Dose / conc.:
50 mg/kg bw/day (actual dose received)
Remarks:
first study
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
200 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10 females and 10 males
Control animals:
yes, concurrent vehicle
Details on study design:
- Rationale for animal assignment (if not random): random

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily for signs of morbidity or mortality.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: monthly

BODY WEIGHT: Yes
- Time schedule for examinations: every week for the first 12 weeks and monthly thereafter

HAEMATOLOGY: Not specified

CLINICAL CHEMISTRY: Not specified

URINALYSIS: Not specified

NEUROBEHAVIOURAL EXAMINATION: Not specified

IMMUNOLOGY: Not specified
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
Gross lesions

HISTOPATHOLOGY: Yes
tissue masses, abnormal lymph nodes, skin, mandibular or mesenteric lymph nodes, mammary gland, salivary gland, sternebrae, bone marrow, thymus, larynx, trachea, lungs and bronchi, heart, thyroid, parathyroid, esophagus, stomach, small intestine, colon, liver, pancreas, spleen, kidneys, adrenals, urinary bladder, prostate/testes or ovaries/uterus, brain and pituitary.
Statistics:
Probabilities of survival were estimated by the product-limit procedure of Kaplan and Meier (1958).
Animals were statistically censored as of the time that they died of other than natural causes or were found to be missing; animals dying from natural causes were not statistically censored. Statistical analyses for a possible dose-related effect on survival used the method of Cox (1972) for testing two groups for equality and Tarone’s (1975) extensions of Cox’s methods for testing for a dose-related trend. All reported P values for the survival analyses are two-sided.
For the statistical analysis of tumor incidence data, two different methods of adjusting for intercurrent mortality were employed. Each used the classical method for combining contingency tables developed by Mantel and Haenszel (1959). Tests of significance included pairwise comparisons of high and low dose groups with controls and tests for overall dose-response trends.


Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One male from the 200 mg/kg dosing group died due to undetermined circumstances.
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
Mean body weight was depressed 10% or more in males that received 100 mg/ kg and in males and females that received 200 mg/ kg (Table 4).
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Compound-related lesions were observed in the forestomach (squamous cell papilloma, hyperkeratosis, and basal cell hyperplasia) and in the liver (minimal to mild centrilobular fatty metamorphosis). Chronic inflammation in the mesenteric lymph nodes was probably secondary to the inflammation or ulceration of the forestomach. Compared with the controls, the three male rats with fatty metamorphosis in the liver had decreased final body weights. However, lower mean body weight gains were also found in other male and female rats administered 200 mg/kg which did not show hepatic fatty metamorphosis.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
At necropsy, the wall of the forestomach of rats was sometimes thickened and the mucosal surface contained small, white papillomatous nodules. When examined microscopically, some nodules were squamous papillomata, having localized acanthosis and papillary projections of the epidermis covered by thick layers of keratinized cells. The basal layer of the epithelium was hyperplastic, sometimes showing finger-like projections into the submucosa. Diffuse hyper keratosis, focal basal cell hyperplasia, or both were usually present in the forestomach of rats without discrete squamous papillomata. In some rats that received 200 mg/ kg, ulceration in the forestomach had completely eroded the epithelium and extended into the muscularis. A few rats without ulcers had circumscribed areas of inflammation in the stomach.
Histopathological findings: neoplastic:
no effects observed

Effect levels

Key result
Dose descriptor:
LOAEL
Effect level:
12.5 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
body weight and weight gain
gross pathology

Target system / organ toxicity

Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
12.5 mg/kg bw/day (actual dose received)
System:
gastrointestinal tract
Organ:
stomach
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes

Applicant's summary and conclusion

Conclusions:
Under the conditions of the study, the LOAEL may be assigned to 12.5 mg/kg bw/day dose. It is however not excluded, that the real LOAEL value may be lower as under given testing conditions. On the other hand, the chronic toxicity of DGRE via oral exposure is not relevant to humans. There was also an opinion, that the observed forestomach tumors were likely to have resulted from an indirect or local toxic effect of DGRE. Therefore by assessing the substance hazard for humans it is essential to identify the effects of toxicity from the other than oral exposure routes.
Executive summary:

Administration of DGRE to rats and mice caused marked toxicity at the sites of direct con- tact (i.e., the esophagus and stomach). In most cases, the stomach lesions seen in animals dying in the 13-week studies were not severe enough to produce death. The presence of macroscopic lesions in the kidney of rats suggests absorption of DGRE, but the exact cause of death was not apparent.

The LOAEL was set at 12.5 mg/kg