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Carcinogenicity

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Description of key information

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
No data
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.
Reason / purpose:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
Groups of male and female rats were maintained for a period of two years on diets containing 1.0, 0.3, 0.1, or 0.03 percent Benax 2A1. On a body weight basis, the test substance was consumed in the amounts of 500, 150, 50, or 15 mg/kg/day by the rats on these levels. General appearance and behavior, mortality, incidence of tumorous growths, food consumption, hematological studfes, serum urea nitrogen and alkaline phosphatase determinations, bone marrow examination, final average body and organ weights, and gross and microscopic examination of the tissues were conducted.
GLP compliance:
no
Species:
rat
Strain:
not specified
Sex:
male/female
Details on test animals and environmental conditions:
Weanling rats from the stock colony of the Biochemical Research Laboratory were placed on a diet of ground Famo Chow and observed for a period of about four weeks before being divided into well matched groups according to body weight of 30 of each sex per group. As many as ten males and ten females in each group were designated to be sacrificed for examination after 12 and 18 months on the experiment. When approximately 50 days of age, the groups of rats were started on diets containing 0.0 (control), 500, 150, 50, or 15 mg/kg/day of Benax 2A1. These levels are equivalent to the administration of 1.0, 0.3, 0.1 and 0.03% Benax 2A1, respectively, in the diet of adult rats. For the first five months of the experiment, the percent of chemical in feed was adjusted according to body weight and food intake in order to administer the specified levels on a mg/kg/day basis. Experimental diets were prepared by thoroughly mixing the test material with the basic diet of ground Famo Chow. After five months of the experiment, the stock diet was changed to ground Purina Laboratory Chow. The rats were caged individually and allowed food and water ad libitum.
Route of administration:
oral: feed
Type of inhalation exposure (if applicable):
other: Not applicable
Vehicle:
unchanged (no vehicle)
Details on exposure:
Rats were given diets containing 0.0 (control), 500, 150, 50, or 15 mg/kg/day of Benax 2A1. These levels are equivalent to the administration of 1.0, 0.3, 0.1 and 0.03% Benax 2A1, respectively, in the diet of adult rats. For the first five months, the percent of chemical in feed was adjusted according to body weight and food intake in order to administer the specified levels on a mg/kg/day basis.
Analytical verification of doses or concentrations:
no
Details on analytical verification of doses or concentrations:
No data
Duration of treatment / exposure:
2 years
Frequency of treatment:
Daily
Post exposure period:
None
Remarks:
Doses / Concentrations:
1.0, 0.3, 0.1 and 0.03% Benax 2A1 and controls
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.0, 500, 150, 50, or 15 mg/kg/day of Benax 2A1
Basis:
nominal in diet
No. of animals per sex per dose:
30/sex/dose
Control animals:
yes, plain diet
Details on study design:
Weanling rats from the stock colony of the Biochemical Research Laboratory were placed on a diet of ground Famo Chow and observed for a period of about four weeks before being divided into well matched groups according to body weight of 30 of each sex per group. As many as ten males and ten females in each group were designated to be sacrificed for examination after 12 and 18 months on the experiment. When approximately 50 days of age, the groups of rats were started on diets containing 0.0, 500, 150, 50, or 15 mg/kg/day of Benax 2A1. These levels are equivalent to the administration of 1.0, 0.3, 0.1 and 0.03% Benax 2A1, respectively, in the diet of adult rats. For the first five months of the experiment, the percent of chemical in feed was adjusted according to body weight and food intake in order to administer the specified levels on a mg/kg/day basis. Experimental diets were prepared by thoroughly mixing the test material with the basic diet of ground Famo Chow. After five months of the experiment, the stock diet was changed to ground Purina Laboratory Chow. The rats were caged individually and allowed food and water ad libitum.

During the course of the experiment, the rats were observed frequently for any changes in appearance or behavior. Each rat was weighed twice a week for the first month, weekly for the next five months, and every two weeks to the end of the experiment. Whenever possible, failing animals were autopsied when moribund in an effort to ascertain the cause of impending death. In addition, records were kept of mortality, and food consumption was recorded , during the second month of the experiment.

Hematological studies, including hematocrit, hemoglobin content, white blood cell count, and differential white cell count were made on five male and five female rats from the control, 1.0, and 0.3% levels after four months on the experiment. At the end of 6, 9, 12, 18, and 24 months, hematological values were obtained from five rats of each sex from each of the groups.

At the end of the two-year period, all surviving rats were fasted overnight, sacrificed by decapitation and examined grossly at autopsy. The lungs, heart, liver, kidneys, spleen, testes, and brain were removed and weighed. Portions of each organ, as well as adrenal, pancreas, urinary bladder, prostate gland, spinal cord, aorta, thymus, peripheral nerve, large intestine, small intestine, stomach, esophagus, pharynx, and skeletal muscle were preserved in formalin, and hematoxylin-eosin stained sections were prepared for microscopic examination. Bone marrow smears were prepared from the femurs of male and female rats on each level and stained with Wrights' s stain. Samples of blood serum were obtained for the determination of urea nitrogen content and alkaline phosphatase activity using the Technicon Auto-Analyzer.

This same procedure was followed for the interim sacrifices after 12 and 18 months.

When appropriate, the Fisher "t" test was used in comparing the mean values obtained on the experimental groups with those of the control; in general, probability values (P) of less than 0.05 were interpreted as indicating a significant difference.
Positive control:
None
Observations and examinations performed and frequency:
During the course of the experiment, the rats were observed frequently for any changes in appearance or behavior. Each rat was weighed twice a week for the first month, weekly for the next five months, and every two weeks to the end of the experiment. Whenever possible, failing animals were autopsied when moribund in an effort to ascertain the cause of impending death. In addition, records were kept of mortality, and food consumption was recorded , during the second month of the experiment.
Sacrifice and pathology:
Hematological studies, including hematocrit, hemoglobin content, white blood cell count, and differential white cell count were made on five male and five female rats from the control, 1.0, and 0.3% levels after four months on the experiment. At the end of 6, 9, 12, 18, and 24 months, hematological values were obtained from five rats of each sex from each of the groups.

At the end of the two-year period, all surviving rats were fasted overnight, sacrificed by decapitation and examined grossly at autopsy. The lungs, heart, liver, kidneys, spleen, testes, and brain were removed and weighed. Portions of each organ, as well as adrenal, pancreas, urinary bladder, prostate gland, spinal cord, aorta, thymus, peripheral nerve, large intestine, small intestine, stomach, esophagus, pharynx, and skeletal muscle were preserved in formalin, and hematoxylin-eosin stained sections were prepared for microscopic examination. Bone marrow smears were prepared from the femurs of male and female rats on each level and stained with Wrights' s stain. Samples of blood serum were obtained for the determination of urea nitrogen content and alkaline phosphatase activity using the Technicon Auto-Analyzer.

This same procedure was followed for the interim sacrifices after 12 and 18 months.
Other examinations:
None
Statistics:
When appropriate, the Fisher "t" test was used in comparing the mean values obtained on the experimental groups with those of the control; in general, probability values (P) of less than 0.05 were interpreted as indicating a significant difference.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
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:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
Groups of male and female rats were maintained for a period of two years on diets containing 1.0, 0,3, 0.1, or 0.03% Benax 2A1. On a body weight basis for adult rats, the test substance was consumed in amounts of 500, 150, 50, or 15 mg/kg/day, respectively, by these groups, For the first five months of the experiment, the percentage levels were adgusted to maintain a uniform administration of Benax 2A1 on a mg/kg/day basis.

In general, all the groups of rats appeared normal in appearance and behavior throughout the experimental period. There was no significant difference in food consumption between the control rats and those receiving the test material in their diets. Records of mortality and incidence of tumorous
growths show no relationship to the inclusion of Benax 2A1 in the diet of rats.

Growth was normal for the groups of rats which received 0.3% (150 mg/kg/day or below) of the test material in feed. The females on the 1.0% (500 mg/kg/day) level began to show growth retardation after six months of the experiment. Slighter growth depression was observed in the male rats on this level.

There was no evidence of adverse effect observed in any of the groups of rats maintained on diets containing Benax 2A1 when compared with the controls as judged by periodic hematological examinations or determination of serum urea nitrogen content and alkaline phosphatase activity.

Twelve Months - Final average body and organ weight ratios showed no significant differences between groups of male control rats and those receiving the diets containing 1.0, 0.3, 0.1 or 0.03% Benax 2A1. The organ/body weight ratios of the kidney and spleen of the females on the 0.1% level and of the liver of the 0.1 and 0.03% females were decreased when compared with the controls. However, these variations were not seen at the higher dose levels and are not considered to be due to the inclusion of Benax 2A1 in the diet of rats. Gross and microscopic examination of the tissues revealed no significant pathological findings in the animals that received the test substance in feed for one year when compared with the controls.

Eighteen Months - A decrease in the final average body weight of the group of female rats on the 1.0% level which were autopsied after 18 months was the only evidence of any adverse effect noted at this time. Gross and microscopic examination of the tissues again showed no significant changes attributable to the test substance.

Twenty-four Months - Upon gross and microscopic examination of the tissues, no significant changes were seen in the animals receiving 1.0, 0.3, 0.1 or 0.03% Benax 2A1 in their diets for two years in comparison with the controls. The final average body weight of the females on the 1.0% level was significantly decreased resulting in an increase in the brain/body weight ratio. The increased testes weight of the male rats which received 1.0 or 0.3% Benax 2A1 in their diets is not considered to be of practical significance.
Relevance of carcinogenic effects / potential:
Not carcinogenic. NOAEL for carcinogenicity was > 1% in the diet or 500 mg/kg bw/day (higest dose group).
Dose descriptor:
NOEL
Effect level:
150 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: NOEL was based on growth depression observed in rats given 500 mg/kg/day or 1.0% in diet. Note: 150 mg/kg bw/day= 0.3% in diet
Remarks on result:
other: Effect type: toxicity (migrated information)
Dose descriptor:
NOAEL
Effect level:
500 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: No treatment-related carcinogenic response observed. No significant differences in tissues of the controls and the test animals up to the highest dosage level (1.0%).
Remarks on result:
other: Effect type: carcinogenicity (migrated information)

None

Conclusions:
The systemic NOEL was determined to be 150 mg/kg bw/day or 0.3% Benax (DOWFAX) 2A1 in the diet. Upon gross and microscopic examination of the tissues, no significant changes were seen in the animals receiving 1.0, 0.3, 0.1 or 0.03% Benax (DOWFAX) 2A1 in their diets for two years in comparison with the controls. NOAEL for carcinogenicity was > 1% in the diet or 500 mg/kg bw/day.
Executive summary:

Groups of male and female rats were maintained for a period of two years on diets containing 1.0, 0.3, 0.1, or 0.03% Benax 2A1 (DOWFAX 2A1) without evidence of adverse effect as judged by general appearance and behavior, mortality, incidence of tumorous growths, food consumption, hematological studies, serum urea nitrogen and alkaline phosphatase determinations, bone marrow examination, final average body and organ weights, and gross and microscopic examination of the tissues. On a body weight basis, the test substance was consumed in the amounts of 500, 150, 50, or 15 mg./kg/day by the rats on these levels.

The only evidence of any adverse effect whatsoever was seen in the rats which received 1.0 percent (500 mg./kg./day) Benax 2A1 in their diets. Growth was depressed in the group of female rats on this level, with a statistically significant decrease in the final average body weight at the end of two years. The group of male rats showed a slighter, statistically insignificant growth retardation.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
500 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
Acceptable quality for evaluation and assessment with highest NOAEL for carcinogenicity. Two different species were tested in 2-year oral chronic studies.

Carcinogenicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

DOWFAX 2A1 was administered in diet up to 1% dose level to rats and dogs over 2 year period. No significant differences in lesion incidence were observed in the tissues of dogs and rats given diets containing up to the highest DOWFAX 2A1 dose compared with the respective controls. NOAEL for carcinogenicity is > 1% in the diet (>319 mg/kg bw/day for dogs and >500 mg/kg bw/day for rats).

Justification for classification or non-classification

In the available studies with DOWFAX 2A1, there is no evidence of tumour formation up to the highest (1% in the diet) doses tested in rats and dogs. DOWFAX family of surfactants is also not genotoxic. Therefore, no CLP classification for carcinogenicity is proposed for this substance.