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Carcinogenicity

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Description of key information

A combined chronic toxicity / carcinogenicity study according to EPA OPP 83-5 was conducted. The dietary exposure of 50 Sprague-Dawley rats per sex and dose to Dicyandiamide (DCD) for up to 104 weeks and up to 50.000 ppm caused no increase in oncogenic effects. 
Two similar study published by Yasuhara et al (1997) and Lewinskas (1963) came to the same conclusion. Feeding Fischer 344 rats with up to 5.0 % (50000 ppm) DCD and albino rats with up to 4% DCD for up to two years exerts no carcinogenic potential under the applied conditions. Overall, DCD exerts no carcinogenic potential in rats when administered for up to two years at doses up to 50000 ppm.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Referenceopen allclose all

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1988 - 1992
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
GLP compliance:
yes (incl. certificate)
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
continuous treatment
Post exposure period:
Not applicable
Dose / conc.:
0 ppm (nominal)
Remarks:
Nominal in diet
Dose / conc.:
5 000 ppm (nominal)
Remarks:
Nominal in diet
Dose / conc.:
15 000 ppm (nominal)
Remarks:
Nominal in diet
Dose / conc.:
50 000 ppm (nominal)
Remarks:
Nominal in diet
No. of animals per sex per dose:
50 animals per sex and dose
Control animals:
yes, concurrent no treatment
Relevance of carcinogenic effects / potential:
No carcinogenic effects/potential
Key result
Dose descriptor:
NOAEL
Effect level:
15 000 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: body weight gain
Dose descriptor:
LOAEL
Effect level:
50 000 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: body weight gain

- 15000 ppm equals 529 mg compound/kg bw/day (males) and 694 mg compound/kg bw/day (females) measured at study week 104.

- 50000 ppm equals 1740 mg compound/kg bw/day (males) and 2424 mg compound/kg bw/day (females) measured at study week 104.

Conclusions:
The toxic effects of dietary administration of Dicyandiamide for at least 52 or 104 weeks to Sprague-Dawley rats at levels of 0, 5000, 15000 or 50000 ppm were limited to significant depression of body weight gain at the 50000 ppm level. There was no increased oncogenic potential associated with compound administration. Under the conditions of this study, 15000 ppm is the NOAEL.
Executive summary:

In a combined chronic / carcinogenicity study, Dicyandiamide (99,8%) was administered to 50 Crl:CD®BR rats/sex/dose in diet at dose levels of 0, 5000, 15000, 50000 ppm for 104 weeks.

The toxic effects of dietary administration of Dicyandiamide for at least 52 or 104 weeks to Sprague-Dawley rats at levels of 5000, 15000 or 50000 ppm were limited to significant depression of body weight gain at the 50000 ppm level. There was no increased oncogenic potential associated with compound administration.

The LOAEL is 50000 ppm, based on reduced body weight gain. The NOAEL is 15000 ppm.

At the doses tested, there was not a treatment related increase in tumor incidence when compared to controls. Dosing was considered adequate based on overt toxicity at the highest dose level.

This chronic/carcinogenicity study in the rats is acceptable and satisfies the guideline requirement for a chronic/carcinogenicity study OECD 453 in rat.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Qualifier:
equivalent or similar to
Guideline:
EPA OPP 83-5 (Combined Chronic Toxicity / Carcinogenicity)
Deviations:
not specified
GLP compliance:
not specified
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Duration of treatment / exposure:
two years
Frequency of treatment:
continuous treatment
Post exposure period:
9 weeks
Dose / conc.:
0 other: %
Remarks:
Nominal in diet
Dose / conc.:
2.5 other: %
Remarks:
Nominal in diet
Dose / conc.:
5 other: %
Remarks:
Nominal in diet
No. of animals per sex per dose:
50 animals per sex per dose
Control animals:
yes, concurrent no treatment
Relevance of carcinogenic effects / potential:
Histopathologically, various tumours developed in all groups, including the control group, but theses were all similar to those known to occur spontaneously in this strain of rats, and no toxicologically significant increase was found for any lesions type in the treated groups.
Dose descriptor:
other: Cyanoguanidine exerts no carcinogenic potential in F344 rats
Effect level:
>= 2.5 - < 5 other: %, nominal in diet
Sex:
male/female
Basis for effect level:
other: overall effects
Remarks on result:
other: no induction of carcinogenicity observed

- There was a dose-related inhibition of body weight gain, attaining statistical significance in both sexes of the 5 % group and in females of the 2.5 % group as compared with the controls from week 1 to 104 and week 1 to 65, respectively.

- After week 108, males and females that had received 2.5 or 5 % cyanoguanidine showed a remarkable increase in their body weight.

- The mean survival time was similar among all tretarment groups.

- The survival rate of the 5 % female group was higher than the other groups

- The incidences of tumours in males were almost 100 % in all groups, while those for females were within the rabge 64 to 78 % with the lowest value observed for females of the 5 % group; There were no statistically significant differences in overall tumour inciddence between the control and treated groups of either sexes.

Conclusions:
On the basis of these results, it is concluded that Cyanoguanidine exerts no carcinogenic potential in F344 rats when administered for up to two years under the conditions of the present study.
Executive summary:

The carcinogenicity of Cyanoguanidine was examined in male and female Fischer 344 rats fed CFR-1 pulverized diets containing 0, 2.5 and 5.0 % Cyanoguanidine for up to two years. The rats were randomly allocated to three groups, each consisting of 50 males and 50 females.

The mean body weight gains in both sexes of the 5 % group and in females of the 2.5 % group were significantly lower than the control values after week 1 of treatment. No other signs of toxicity were seen in any of the rats throughout the treatment period. Histopathologically, various tumours developed in all groups, including the control group, but theses were all similar to those known to occur spontaneously in this strain of rats, and no toxicologically significant increase was found for any lesions type in the treated groups.

On the basis of these results, it is concluded that Cyanoguanidine exerts no carcinogenic potential in F344 rats when administered for up to two years under the conditions of the present study.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Apr 1960- Apr 1962
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline available
Principles of method if other than guideline:
pre GLP, pre OECD, 2y feeding study in rats
GLP compliance:
no
Species:
rat
Strain:
other: Nelson Colony albino rats
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Carworth Farms
- Age at study initiation: 1 month
- Diet: ad libitum
- Water: ad libitum

IN-LIFE DATES: From: April 1960 To: April 1962
Route of administration:
oral: feed
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
106 weeks
Frequency of treatment:
continously
Post exposure period:
no
Dose / conc.:
0 other: %
Remarks:
Nominal in diet
Dose / conc.:
0.25 other: %
Remarks:
Nominal in diet
Dose / conc.:
1 other: %
Remarks:
Nominal in diet
Dose / conc.:
4 other: %
Remarks:
Nominal in diet
No. of animals per sex per dose:
50 (control); 25 (low dose; mid dose); 28 (high dose)
Control animals:
yes, plain diet
Details on study design:
The animals, their diet, and the design of the study have been described in Report No. 61-5 (not available).
Individual body weights where recorded bi-weekly from 3 months to the end of the first year, after which time they were recorded at monthly intervals. During the 81st week of the study, animals were moved in an air-conditioned truck from Stamford, Connecticut to new laboratory facilities located at the Agricultural Center in Princeton, New Jersey. Housing facilities at Princeton were similar to those described in report 61-5, except that the rooms were windowless.
Positive control:
no
Sacrifice and pathology:
GROSS AND Microscopic PATHOLCGY: At the end of the study, all animals were sacrificed and given a thorough gross autopsy which included opening the skull. Thyroid, heart, liver, adrenal, spleen, kidney and pituitary were weighed for 10 animals of each sex from each group. Details of autopsy procedures and sample preservation, preparation and examination of tissues are presented in Central Medical Department Report No. 63-18 entitled “Dicyandiamide: Two-Year Feeding to Rats. Pathology Supplement"
Other examinations:
HEMATOLOGY: Hemoglobin, hematocrit and total and differential leukocyte count were performed on 5 males and 5 females from each dietary level and the control group after 12 and 24 months of feeding. The same animals were used as previous insofar as possible, and the same procedures were employed as described in Central Medical Department Report No. 61-5.
Statistics:
yes for bw, food intake and organ weights
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
body weight reduced at 4% (m+f) and 1% (f)
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
no treatment related effects
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY

The overall appearance and behavior of the experimental animals at all feeding levels was comparable to the controls throughout the 2 year experimental period. The usual observations of intermittent soft feces, colds with resulting pneumonitis, ulcerative decubitus ulcers, tumors and nasal and ocular porphyrin excretion and sore eyes were noted in both experiment and control groups and did not appear to be related to either dietary level or to sex. The findings were also comparable to those noted in other 2-year studies in these laboratories with the same strain of rat. Autopsy protocols, list these observations under individual animals.
Survival of the experimental animals was comparable to the controls over the 24-month feeding period. When compared on the basis of the ratio of the total number of days the animals actually lived to the theoretical maximum number of days available on the study, and expressed as percent of theoretical, survival was in excess of 90% for all groups. Data are calculated on the basis of 105 weeks. DCD appears to have no effect on survival when included in the diets of rats at levels of 4%, or less.

BODY WEIGHT AND WEIGHT GAIN

Individual weight gain and food consumption for all survivors of the study at 105 weeks are reported. Body weight gain was subjected to statistical analysis. It was concluded that 4.0% DCD was clearly depressive of body weight gain on both sexes over the major portion of the 2-year period. At the 1.0% level, females had a significantly decreased body weight gain during a large part of the second year of the study, while body weight of 1.0% males did not differ from that of controls. There were no significant differences in mean body weight between the 0.25% DCD groups and their respective controls. The 2 instances, 73 and 81 weeks, when body weight of 0.25% females was significantly below that of their controls are judged to be of no consequence since mean body weight of this group was not distinguishable from the controls over the rest of the 2-year period.
Since there was a numerical decrease in body weight gain of test females, albeit not a significant decrease at the 0.25% DCD level, it was felt that this might be reflected in feed intake among females. Therefore, the analysis in Part II of Appendix B was undertaken. At 3-month
intervals, the number of times that test females ate less than their controls was calculated, and the probability of occurrence of such decreases was computed. It was found that the frequency with which test females ate less than their controls was significantly greater than that which would be expected by chance alone (P<.05) as follows: 0.25% from 27 to 91 weeks; l.0% from 0-91 weeks and 4.0% from 0-104 weeks. Since food intake of test females frequently was less than that of their controls, this contributed, at least in part, to their lesser weight gains.

HAEMATOLOGY
Hematological values determined after 12 and 24 months on test are reported, including mean values for hematocrit, hemoglobin and total leukocytes. Mean hematocrit and mean hemoglobin values were compared according to the method of Dunnett (J. Am. Statis. Assoc.; 50: l096, 1955) using one-sided comparison at the 95% confidence interval.
At 24 months, females receiving l.0% DCD had a moderate, significant increase in mean hematocrit value, compared to their controls. All other test groups had mean hematocrits comparable to their controls after 12 and 24 months on test.
Mean hemoglobin values showed a slight, but significant, decrease for 0. 25% males at 12 months, and a moderate increase for l.0 % females at 24 months.
All other mean hemoglobin values at 12 and 24 month did not differ significantly
from corresponding control values.
Since mean hematocrit and mean hemoglobin values for the 4.0% DCD group did not differ from their corresponding control values at the end of the study, and since such deviations as were noted were sporadic and not dose-related, it is concluded that feeding of DCD did not affect hematocrit or hemoglobin of rats.
Total and differential leukocyte counts were examined visually. The observed values are comparable for test and control animals, and reflect the variability encountered in studies of this nature. It is judged that feeding of DCD was without effect on the number or distribution of
leukocytes.

ORGAN WEIGHTS
Weights of organs determined at time of sacrifice are reported. Statistical evaluation was limited to heart, liver and kidney, expressed as percent of body weight. There were no significant differences in mean heart weight, expressed in percent of body weight between any test group and its corresponding control. Mean liver weight of test females did not differ significantly from that of female controls. Among males, the 1.0% and 4.0% DCD groups had significant decreases in mean liver weight. The observed decrease for the 4.0% group which was just at the 95% confidence level, was smaller
than the decrease for the 1.0% group. Since the effect is obviously not dose-related, and since mean liver weight of the 0.25% group did not differ significantly from that of the controls, it is concluded that feeding of DCD did not have an adverse effect on mean liver weight. Mean kidney weight of females fed DCD did not differ significantly from mean kidney weight of control females. Control males had a mean kidney weight which was significantly higher than that of male test groups. Since mean kidney weight of test males was nearly identical for all levels of feeding, there is no dose-related effect. 3 rats had chronic interstitial nephritis and cysts, which contributed to enlargement of the organs. It is judged that these 3 enlarged kidneys distort the value for mean kidney weight of control males, thus preventing a reliable assessment of results. Consequently, mean kidney weight of control males was recalculated for the 7 remaining animals. The mean value, 0.69 percent of body weight, does not differ significantly from that of the test
groups. On this basis, it is concluded that feeding of DCD has no adverse effect on kidney weight of males. A review of the absolute weights of other organs came to a conclusion that there was no adverse effect attributed to feeding of DCD. The weights of these organs are comparable in range for test and control groups and are similar to those encountered in previous studies. An occasional animal has a somewhat enlarged adrenal or spleen, and a few animals have enlarged pituitaries. It should be noted that the latter condition is fairly common in this strain of rat. A female receiving 1.0% DCD had an unusually small pituitary.

HISTOPATHOLOGY:
A number of animals died of various causes in the course of the trial. Individual autopsy
reports on these animals are given. Because of autolytic changes, many could not be autopsied satisfactorily. Of those which could be examined, no lesions were encountered which suggested Dicyandiamide-induced change. Varying degrees of autolysis among these animals makes presentation of the autopsy data in tabular form of questionable value. This is, therefore, not attempted. This is less true of animals with tumors since by their size, color and other characteristics, neoplasms may often be recognized even though moderate degrees of autolysis be present. Accordingly, the type and incidence of tumors among spontaneously dying animals is given. No effect of DCD could be detected.
At the completion of 2 years of feeding, all survivors were anaesthetized with chloroform, killed by bleeding from the posterior aorta, and autopsied. Ten animals of each sex on each feeding level were selected at random and the major organs weighed. Five of each sex and each level of these were likewise selected for histopathologic study. The following organs were fixed in 10% buffered formalin, sectioned, and stained with hematoxylin and eosin for microscopic examination: skeletal muscle, spleen, mesenteric lymph node, liver, stomach, ileum, caecum, colon, urinary bladder, gonads, prostate or uterus, seminal vesicle or vagina, adrenals, kidneys, thyroid and when possible parathyroid, trachea, esophagus, lung, heart, and brain. Picuitary was stained with periodic acid- Schiff-orange G, pancreas was fixed in sodium acetate-mercuric chloride formalin before staining, femurs and marrow were decalcified in formic acid and stained with Giemsa stain. A07 lesions whose nature was not grossly obvious in animals other than the above-mentioned "selected" animals were also examined microscopically. All tumors were examined microscopically with the exception of a few obviously benign mammary fibro-adenomas.
No gross or microscopic lesions referable to the feeding of DCD were encountered.
On all groups of males, testicular atrophy and chronic infectious nephritis, either of the interstitial or pyelo-types were common. In the female groups, there were frequent pituitary adenomas, cystic ovaries and adrenal cortical hemorrhages. Common to both sexes of all groups were chronic pneumonia, chronic bronchitis and peribronchitis and otitis media. Cage sores (infected decubitus ulcers) were common only in the large heavy males, and not in the females. An interesting incidental finding was the occurrence of a. small inflamed mammary gland in one of the 1.0% males.
Dose descriptor:
LOAEC
Effect level:
40 000 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: reduced body weight gain
Remarks on result:
other: Effect type: toxicity
Dose descriptor:
NOAEC
Effect level:
10 000 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: toxicity
Dose descriptor:
conc. level:
Effect level:
>= 40 000 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no increase in the incident of neoplasm or other histopathological lesions
Conclusions:
Feeding of levels of Dicyandiamide as high as 4% of the diet did not result in incidences of mortality, disease lesions, or neoplasms significantly different from those of the control animals.
Executive summary:

In a carcinogenicity study, Dicyandiamide was administered to 25 – 50 albino rats/sex/dose in diet at dose levels of 0, 2500, 10000, 40000 ppm for 106 weeks.

There were no compound related effects in mortality, clinical signs, food consumption, hematology, clinical chemistry, urinalysis, organ weights, or gross and histologic pathology. Body weight was slightly decreased in the high dose group in both sexes, and in females of the mid dose group. The LOAEL is 40000 ppm, based on body weight. The NOAEL is 10000 ppm.

At the doses tested, there was not a treatment related increase in tumor incidence when compared to controls. Dosing was considered adequate.

This carcinogenicity study in the rat is acceptable and does satisfy main aspects of the guideline requirement for a carcinogenicity study in rats.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Study duration:
chronic
Species:
rat

Carcinogenicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Based on the findings of two long-term feeding studies DCD exerts no carcinogenic potential in rats when administered for up to two years under the applied conditions at doses up to 50000 ppm (equals 1740 mg/kg bw/day in males and 2424 mg/kg bw/day in females, respectively, based on compound consumption in week 104).


Justification for classification or non-classification

DCD exerts no carcinogenic potential in rats when administered for up to two years at doses up to 50000 ppm.