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Administrative data

Description of key information

Sprague-Dawley rats were used in this study. 20 males and 20 females were assigned to control, and to each of the test groups (25, 100 and 400 mg/kg). The length of the treatment period was 90 days.

One animal in the mid-dose group (100 mg/kg) died after 12 days of treatment but was an isolated case and so not related to administration of test material.  Animals were generally healthy during the study, but exhibited alopecia around the nares and paws, diarrhea, watery eyes (animals that were bled, only) and encrustment around the nares. These signs were attributed to ingestion of a powdered food and were not considered to be related to test material.  

Food intake was measured weekly, other than a random week where a particular test group ate less food than comparable test groups or control groups, there was no significant difference in food intake between control and test animals in any sex grouping. Animals were weighed initially and then weekly thereafter. Weight gains were essentially comparable in treated and control groups with only a sex difference noted; males gained more weight than females.

Gamma-glutamyl transpeptidase (GGTP), glutamix-oxaloacetic transpeptidase, glutamic-pyruvic transaminase and urea were measured at 90 days in 5 males and 5 females from each test group. GGTP values were variable within the different dose groups but were within the values usually observed in this strain of rat. Glucose levels of treated animals were lower than controls but were within the range of normal values reported for this strain of rat. Since there were not statistically significant differences between the means of treated animals, the significant difference between the high-dose females and their control was considered to be a result of some unusually high values among the controls and was not considered to be the result of administering the test material. Glutamic-oxaloacetic transaminase, Glutamic-pyruvic transaminase and urea were unaffected by the treatment.

At 45 days, no changes in erythrocyte counts were noted. At 90 days, there was a trend toward increased red blood cells in low and mid-dose animals; however, counts in high dose animals were similar to controls. Since the increase was not dose-related, this observation was thought to be artifactual in nature and not related to administration of test material. There were no changes in hematocrit, hemoglobin, leukocyte count, platelet estimate and erythrocyte morphology.

There was no effect of treatment on urinalysis, organ weights, or gross pathology.  One of the males with a high GGTP value had focal perivascular and periductal mononuclear leukocyte infiltration in the liver, but the other animal did not demonstrate any liver pathology.  Livers of other males in the high dose group had histopathology similar to that of controls.  Other mild inflammatory lesions characterized by leukocytic infiltration also occurred in the lungs, liver and kidneys of a few animals in each group.  All changes were considered to be spontaneous and not related to administration of test material.

Therefore it is concluded that the test material did not affect adversely the rats after 90 days of administration at the highest dose tested. The NOAEL is 400 mg/kg bw.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1977
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Doses of test material, homogeneous distribution, and stability in the diet were not confirmed analytically. More hematological, clinical chemistry and urinalysis parameters are measured in guideline studies. A high enough dose to produce a significant toxicological effect was not used.. GLP was not formally followed and no reference was made to following a specific guideline.
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
Test method was a standard multidose study for the time period, with a control group.
GLP compliance:
no
Limit test:
no
Specific details on test material used for the study:
CYANOX® 1790 Antioxidant
IUPAC nomenclature - Tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate
Synonym - [tris(4-t-butyl-3-hydroxy-2,6-dimethyl-benzyl)-s-triazine-2,4,6-(1H,3H,5H) trione]
Lot A-1790 PP 76-2
Appearance - White powder, odorless
CAS No. 40601-76-1
Molecular Formula - C42H57N3O6
Molecular Weight - 699.92 g/mole
Purity 90.9%
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories Incorporated, Massachusetts
- Age at study initiation: 4 weeks
- Weight at study initiation: 69-100g (males); 64-95g (females)
- Housing: Individually housed in suspended stainless ssteel cages with wire mesh bottoms.
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-24
- Humidity (%): 40-50
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
oral: feed
Vehicle:
not specified
Details on oral exposure:
Test diets were prepared by mixing the appropriate amount of test material with equal amounts of ground Purina Lab Chow in a high speed blender (blending time was not noted). After blending, an additional 2 parts of ground lab chow was mixed by hand into the blended material. After this step, an additional amount of ground lab chow was added to give the appropriate dose level (25 mg/kg bw, 100 mg/kg bw or 400 mg/kg bw). The diet was then placed in a twin-shell mixer and mixed until the test material was distributed throughout the diet. The formula used to determine the amount of material added to feed was as follows: mean body weight x dietary level x 7 days/mean weekly food consumption = mg test material/kg feed. Fresh diets were prepared at least once per week. Doses were adjusted weekly on the basis of the weight and food consumption for the preceding week. Doses were not adjusted for purity of the material.
Analytical verification of doses or concentrations:
no
Duration of treatment / exposure:
90 consecutive days
Frequency of treatment:
Daily in diet
Dose / conc.:
0 mg/kg bw/day (nominal)
Dose / conc.:
25 mg/kg bw/day (nominal)
Dose / conc.:
100 mg/kg bw/day (nominal)
Dose / conc.:
400 mg/kg bw/day (nominal)
No. of animals per sex per dose:
20
Control animals:
yes, plain diet
Details on study design:
- Dose selection rationale: Based on a 30d range-finding study (see other study record available)
- Fasting period before blood sampling for clinical biochemistry: overnight
Positive control:
No positive control reported
Observations and examinations performed and frequency:
Food consumption and body weights were measured weekly. Animals selected for clinical chemistry, hematology and urinalysis (5 per sex per group) were determined by protocol and a table of randomization. Clinical chemistry (gamma-glutamyl transpeptidase, glucose, glutamic-oxaloacetic transaminase, glutamic pyruvic transaminase, and blood urea nitrogen), hematology (erythrocyte count, hematocrit, hemoglobin, differential and total leukocyte count, and platelet count) and urinalyses (appearance, glucose, microscopic examination of sediment, pH, protein and specific gravity) were performed on the same animals at appropriate time intervals (day 90 for clinical chemistries, days 45 and 90 for hematologies). Animals were fasted overnight before blood was collected from the orbital sinus on day 45 and from an unknown site on day 90. Urine also was collected on days 45 and 90.
Sacrifice and pathology:
At study termination, all animals were weighed. They were then euthanized. The urogenital orifaces, tail, each pinna, eyes and external auditory meatus were examined visually and by palpatation for distortions. All subcutaneous tissues were examined including regional lymph nodes, mammary and salivary glands. Abdominal contents, and the brain, pituitary gland and cranial nerves also were examined grossly. The following tissues were taken and preserved for possible histologic evaluation: adrenal, aorta, urinary bladder, bone, bone marrow, cerebellum, cerebrum, pancreas, pituitary, skin , stomach, thyroid, colon, esophagus, eye, heart, ileum, jejunum, kidney, prostate, salivary gland, spleen, testes, tongue, uterus, liver, lung, lymph node, mammary gland, muscle (skeletal), sciatic nerve, ovary, parathyroid, seminal vesicle, spinal cord, thymus and trachea. Any organ or tissue exhibiting a lesion was noted and the lesion was taken for histopathological examination. Complete histopathology was performed on 10 animals/sex/group from the control and high dose groups. These animals were selected randomly from a table. Microscopic examination of the heart, liver, lungs and kidneys was performed on all additional animals that survived to termination.
Statistics:
Data for food intake, weight gain, clinical chemistries, hematologies, urinalyses, and organ weights were analyzed using a blocked 2-way analysis of variance that compared data between and within groups. If F values were significant, data were compared using Dunnett's t-test. The level of significance is p < 0.05.
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
Grossly observable deviation from normal was seen in all groups. These deviations included alopecia around the nares and front paws, diarrhea, watery eyes and encrustment around nares. The alopecia appeared and disappeared in all groups throughout the study and was attributed to mechanical irritation due to movement in and out of the feeding container. The diarrhea was seen in an occasional individual in all groups at various periods, and was not considered to be related to the test material. No animal had diarrhea for two consecutive days. Watery eyes appeared primarily immediately after orbital bleeding of some animals for hematology and clinical chemistry determination and was considered to be the result of bleeding. Encrustment around nares is common to animals fed compound mixed in feed. There were no clinical signs manifested in this study attributable to the test material up to and including 400 mg/kg
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One animal in the mid-dose group (100 mg/kg) died after 12 days of treatment. Since no additional deaths occurred, this death was considered artifactual.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
There were no significant differences in weight changes among treated groups when compared to control throughout the entire study.
Food consumption and compound intake (if feeding study):
effects observed, non-treatment-related
Description (incidence and severity):
During first week on test, females in the 25 mg/kg treated group ate significantly less food than did the other female groups during that week. Males in the 25 mg/kg treated group ate less food than the other males during the third week on test. No other effets of the test material were seen upon food intake throughout the 13 weeks of the study. Therefore, it was concluded that dose levels up to 400 mg/kg bw of feed did not affect food intake in rats.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
After 45 days on study there was no significant difference in erythrocyte count in either males or females.
At 90 days, there was a trend toward increased red blood cells in low (8.27 x 10E6/mm3) and mid-dose animals [(8.63 x 10E6/mm3, value significantly different from study control (7.99 x 10E6/mm3) and historical controls]; however, counts in high dose animals (8.04 x 10E6/mm3) were similar to controls. Since the increase was not dose-related, this observation was thought to be artifactual in nature and not related to administration of test material.

There were no changes in hematocrit, hemoglobin, leukocyte count, platelet estimate and erythrocyte morphology.
Clinical biochemistry findings:
effects observed, non-treatment-related
Description (incidence and severity):
Gamma-glutamyl transpeptidase (GGTP) values in males treated with 400 mg/kg were higher than control at 90 days (4.1 vs. 2.6 IU/l), but were within historical limits. The elevation was due to 2/5 males that had GGTP values that were twice the value of the other males. This effect was not seen in females. Since this elevation of GGTP was not dose related in males and since females did not have a change in GGTP values, it was concluded that this observation was not treatment-related.
Glucose values in females treated with 100 and 400 mg/kg (163 and 162 mg/dl, respectively) were lower than controls (209 mg/dl) at 90 days but were within the range of historical values (90-284 mg/dl). This effect was not seen in males. The significant differences in glucose between high and mid dose females and controls were considered to be a result of some unusually high values in the controls and were similar to the historical means. Therefore this effect was not considered to be related to test material.

Glutamic-oxaloacetic transaminase, Glutamic-pyruvic transaminase and urea were unaffected by the treatment.
Urinalysis findings:
no effects observed
Description (incidence and severity):
There were no differences in the color, appearance, pH, specific gravity, milligram protein, milligram sugar, RBC see under a high power field, and WBC seen under a high power field in rats fed the test material for 90 days.
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
No differences in weight of hearts, livers, kidneys, gonads or brain.
Gross pathological findings:
no effects observed
Description (incidence and severity):
There were no descernable changes in most rats in each group. The few changes noted were considered unrelated by type or incidence to the administration of the test material. The gross pathological changes were not unlike those with spontaneous lesions to the laboratory rat of this age group. The lesions included artifacts of necropsy procedures (discoloration of tissue due to congestion); physiological changes (alteration in size of endocrine gland) and spontaneous inflammatory processes (pneumonia, arthritis, etc.). Each tissue with a gross change was examined microscopically to determine if histological correlation could be detected. No related histopathological correlation could be detected. Therefore, it was concluded that alterations seen at necropsy are unrelated to the treatment and have no apparent biological significance.
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
The type and incidence of lesions detected by the histopathological examination were considered to represent spontaneous change in albino rats and unrelated to the administration of the test material.
Histopathological findings: neoplastic:
not specified
Details on results:
One animal in the mid-dose group (100 mg/kg) died after 12 days of treatment. Study personnel did not attribute this death to administration of test material. Animals were generally healthy during the study, but exhibited alopecia around the nares and paws, diarrhea, watery eyes (animals that were bled, only) and encrustment around the nares. Study personnel attributed these signs to ingestion of a powdered food and did not consider them to be related to test material. Other than week one (where females treated with 25 mg/kg test material ate less food than females in other groups) and week 3 (when males in the 25 mg/kg group ate less food than males in the other groups), there was no difference between food intake of treated and control animals. There was no effect of treatment on weight or weight gain.

Gamma-glutamyl transpeptidase (GGTP) values in males treated with 400 mg/kg were higher than control at 90 days (4.1 vs. 2.6 IU/l), but were within historical limits. The elevation was due to 2/5 males that had GGTP values that were twice the value of the other males. This effect was not seen in females. Since this elevation of GGTP was not dose related in males and since females did not have a change in GGTP values, it was concluded that this observation was not treatment-related. Glucose values in females treated with 100 and 400 mg/kg (163 and 162 mg/dl, respectively) were lower than controls (209 mg/dl) at 90 days but were within the range of historical values (90-284 mg/dl). The significant differences in glucose between high and mid dose females and controls were considered to be a result of some unusually high values in the controls and were not considered to be related to test material.

At 90 days, there was a trend toward increased red blood cells in low (8.27 x 10E6/mm3) and mid-dose animals [(8.63 x 10E6/mm3, value significantly different from study control (7.99 x 10E6/mm3) and historical controls]; however, counts in high dose animals (8.04 x 10E6/mm3) were similar to controls. Since the increase was not dose-related, this observation was thought to be artifactual in nature and not related to administration of test material.

There was no effect of treatment on urinalysis, organ weights, or gross pathology. One of the males with a high GGTP value had focal perivascular and periductal mononuclear leukocyte infiltration in the liver, but the other animal did not demonstrate any liver pathology. Livers of other males in the high dose group had histopathology similar to that of controls. Other mild inflammatory lesions characterized by leukocytic infiltration also occurred in the lungs, liver and kidneys of a few animals in each group. All changes were considered to be spontaneous and not related to administration of test material.
Dose descriptor:
NOAEL
Effect level:
400 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Remarks on result:
other: No adverse effects noted at the highest dose tested
Critical effects observed:
no
Conclusions:
The changes that were observed (elevated gamma-glutamyl transpeptidase in high dose males, decreased glucose in females, and increased red blood cell counts in mid-dose males at 90 days) were not considered to be related to test material since they were not dose-dependent and were within normal limits. Therefore, the NOAEL was 400 mg/kg bw.
Executive summary:

Sprague-Dawley rats were used in this study. 20 males and 20 females were assigned to control, and to each of the test groups (25, 100 and 400 mg/kg). The length of the treatment period was 90 days.

One animal in the mid-dose group (100 mg/kg) died after 12 days of treatment but was an isolated case and so not related to administration of test material.  Animals were generally healthy during the study, but exhibited alopecia around the nares and paws, diarrhea, watery eyes (animals that were bled, only) and encrustment around the nares. These signs were attributed to ingestion of a powdered food and were not considered to be related to test material.  

Food intake was measured weekly, other than a random week where a particular test group ate less food than comparable test groups or control groups, there was no significant difference in food intake between control and test animals in any sex grouping. Animals were weighed initially and then weekly thereafter. Weight gains were essentially comparable in treated and control groups with only a sex difference noted; males gained more weight than females.

Gamma-glutamyl transpeptidase (GGTP), glutamix-oxaloacetic transpeptidase, glutamic-pyruvic transaminase and urea were measured at 90 days in 5 males and 5 females from each test group. GGTP values were variable within the different dose groups but were within the values usually observed in this strain of rat. Glucose levels of treated animals were lower than controls but were within the range of normal values reported for this strain of rat. Since there were not statistically significant differences between the means of treated animals, the significant difference between the high-dose females and their control was considered to be a result of some unusually high values among the controls and was not considered to be the result of administering the test material. Glutamic-oxaloacetic transaminase, Glutamic-pyruvic transaminase and urea were unaffected by the treatment.

At 45 days, no changes in erythrocyte counts were noted. At 90 days, there was a trend toward increased red blood cells in low and mid-dose animals; however, counts in high dose animals were similar to controls. Since the increase was not dose-related, this observation was thought to be artifactual in nature and not related to administration of test material. There were no changes in hematocrit, hemoglobin, leukocyte count, platelet estimate and erythrocyte morphology.

There was no effect of treatment on urinalysis, organ weights, or gross pathology.  One of the males with a high GGTP value had focal perivascular and periductal mononuclear leukocyte infiltration in the liver, but the other animal did not demonstrate any liver pathology.  Livers of other males in the high dose group had histopathology similar to that of controls.  Other mild inflammatory lesions characterized by leukocytic infiltration also occurred in the lungs, liver and kidneys of a few animals in each group.  All changes were considered to be spontaneous and not related to administration of test material.

Therefore it is concluded that the test material did not affect adversely the rats after 90 days of administration at the highest dose tested. The NOAEL is 400 mg/kg bw.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
400 mg/kg bw/day
Study duration:
subchronic
Species:
rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Repeated dose toxicity

In a key study conducted in rats, groups of 20 COBS Sprague-Dawley rats/sex/dose were treated with the test material in the diet for 90 days at nominal dose levels of 0, 25, 100 or 400 mg/kg bw/d. Elevated gamma-glutamyl transpeptidase (GGTP) in high dose male rats, decreased glucose in females and increased red blood cell counts in mid-dose males at 90 d were not considered to be treatment related since effects were not dose related and were within normal limits for the measured endpoints. The NOAEL was reported as 400 mg/kg bw/d.

In a 30-d range finding study, groups of 5 Sprague-Dawley rats/sex/dose were treated with the test material in the feed at 0, 0.5, 1.0 or 2.0%. At necropsy, discoloration of the livers in 2 high dose males and 2 high dose females was present but there were no corresponding histopathological effects that correlated in 3 of 4 of these. One high-dose male displayed minimal intralobular scattered foci of extra medullary hematopoiesis with mononuclear infiltrates. It was concluded that liver effects were not due to test material. There was a significant trend toward increased food consumption in females, with the value at week 4 significantly different from control. The NOAEL reported was 1190 mg/kg bw/d (1% in diet) and the LOAEL was 2380 mg/kg bw/d (2% in diet).

In older supporting studies, dogs have been treated with the test material in the diet for up to 90 days with only minimal effects observed. In the first of two 90-day studies, groups of 4 beagle dogs/sex/dose were treated with the test material in the diet at 46 mg/kg bw/d (actual ingested) for 13 weeks. No significant effects related to compound administration were identified in this study. The NOAEL was reported as 46 mg/kg bw/d. In a separate 90-day study, groups of 4 beagle dogs/sex/dose were treated with the test material in the diet for 90 days at dose levels of 0, 7.5, 15.0 or 30.0 mg/kg bw/d. In this study, reduced body weights in female dogs at the highest dose were not considered treatment related because food consumption was comparable among groups and there were no abnormal clinical signs. There were no other significant treatment-related changes. The NOAEL was reported as 30 mg/kg bw/d.

In a range-finding study conducted in conjunction with an OECD 421 reproductive effects screening study, groups of 6 Sprague-Dawley rats/sex/dose were treated with the test material in the diet at 0, 1000, 10000 or 20000 ppm (0, 50, 500, 1000 mg/kg/day) for 14 days. No significant toxicological findings were reported.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
A well-conducted study in rats by the most appropriate exposure route

Justification for classification or non-classification

In well conducted repeated dose oral toxicity studies in rats, no significant toxicity was noted up to a dose level of 400 mg/kg bw/day. No classification is warranted for repeated-dose effects.