Cyanamide

Repeated dose toxicity: dermal

Administrative data

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1996

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Stability, homogeneity and correctness of the concentrations not verified analytically; 3 males and 3 females used per concentration instead of 5 males and 5 females; no sacrifice immediately after end of application, but after 14-day; body weight 1200 g ± 200 g instead of 2000 – 3000 g at the beginning of treatment; housing temperature 24 ± 2 °C instead of 20 ± 3 °C; no summary or individual data of clinical findings; less haematological and blood chemistry parameter compared to OECD 410; no individual organ weight data were submitted.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1996

Report date:

1996

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Gaitonde Committee guidelines

Deviations:

no

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Cyanamide

EC Number:

206-992-3

EC Name:

Cyanamide

Cas Number:

420-04-2

Molecular formula:

CH2N2

IUPAC Name:

cyanamide

Test material form:

other: aqueous solution

Details on test material:

- Test substance: Dormex (Hydrogen cyanamide, aqueous solution)
- Physical state and appearance: Light blue coloured, liquid
- Purity: 50 % w/w formulation
- Lot/Batch number: 507401

Test animals

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Body weight: 1200 ± 200 g
- Housing temperature: 24 ± 2 °C

Administration / exposure

Type of coverage:

not specified

Vehicle:

unchanged (no vehicle)

Details on exposure:

Not indicated

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

No analytical verification of doses or concentrations was performed

Duration of treatment / exposure:

six hours per day on 5 days per week for three consecutive weeks followed by a 14 day post-application observation period.

Frequency of treatment:

Daily treatment

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

25 mg/kg bw/day (nominal)

Remarks:

equivalent to 12.5 mg/kg bw/day active substance Cyanamide
nominal per unit body weight

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day (nominal)

Remarks:

equivalent to 25 mg/kg bw/day active substance Cyanamide
nominal per unit body weight

Doses / concentrations 3

Dose / conc.:

75 mg/kg bw/day (nominal)

Remarks:

equivalent to 37.5 mg/kg bw/day active substance Cyanamide
nominal per unit body weight

No. of animals per sex per dose:

3 animals per sex per dose

Control animals:

yes, concurrent no treatment

Details on study design:

- The concentrations were selected according to the results of a pilot study

Positive control:

No positive control

Examinations

Observations and examinations performed and frequency:

The animals were examined once daily for mortalities, clinical symptoms and local skin irritations. Data of body weight and food consumption of individual rabbits were recorded weekly. Clinical-chemical and haematological investigation and urinalysis were performed on day 0, 22 and 35.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

No other examinations

Statistics:

The difference between the control groups and the test-dose groups were examined by the Student´s test criteria, p< 0.05.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Dermal irritation:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

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:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

There were no mortalities in any groups of the test material or post-application observation period. At the highest concentration severe erythema of the skin and reduction in the fur density around the areas of application were observed. Slight erythema during the application period were observed at the mid dose of 25 mg/kg bw/day pure active substance cyanamide which recovered one day after application. There were no significant differences in the body weight and feed consumption of animals treated with Dormex when compared to the control animals. None of the haematological, clinical chemical and urine parameters of the treated groups showed any statistical significant variation as compared to the controls at each time of measurement.
After the recovery period some organ weights revealed a statistical significance in the low, mid or high dose males. However, due to the fact that there are no consistent dose-dependent changes the findings are considered to be incidental.
The gross pathological and histopathological examinations showed no consistent findings in the low and mid dose animals. Some high dose animals showed findings even after the 14 d recovery period.

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

25 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

clinical signs

gross pathology

histopathology: non-neoplastic

mortality

Target system / organ toxicity

Key result

Critical effects observed:

no

Lowest effective dose / conc.:

37.5 mg/kg bw/day (nominal)

System:

other: histopathological examinations revealed lesions in several tissues/organs, no clear target system

Any other information on results incl. tables

Table 1: Subacute (21-Day) dermal toxicity study in Rabbits: Organ Weights

Pure active ingredient cyanamide	0 mg/kg bw/day	12.5 mg/kg bw/day	25.0 mg/kg bw/day	37.5 mg/kg bw/day
Males:
Absolute heart weight (g)	3.925	3.058*	3.848	3.041*
Relative^aheart weight ( %)	0.257	0.162	0.226	0.171
Absolute liver weight (g)	31.667	45.333*	58.000*	45.667*
Relative^aliver weight ( %)	2.074	2.410	3.433*	2.566
Absolute kidney weight – left (g)	5.315	3.897**	5.207	4.165**
Relative^akidney weight – left ( %)	0.347	0.208**	0.307	0.234
Absolute kidney weight – right (g)	5.515	4.230*	5.137*	4.206*
Relative^akidney weight – right ( %)	0.360	0.226**	0.303	0.236**
Absolute gonad weight – left (g)	0.917	1.620	1.064	2.099
Relative^agonad weight – left ( %)	0.059	0.086	0.063	0.118*
Absolute gonad weight – right (g)	0.929	1.587*	1.254	2.095
Relative^agonad weight – right ( %)	0.060	0.084	0.068	0.118*
Females:
Absolute heart weight (g)	4.383	2.941	4.329	3.310
Relative^aheart weight ( %)	0.261	0.153	0.217	0.180
Absolute liver weight (g)	41.000	48.333	54.000	39.667
Relative^aliver weight ( %)	2.480	2.521	2.704	2.152
Absolute kidney weight – left (g)	4.950	3.819	4.777	3.847
Relative^akidney weight – left ( %)	0.290	0.200	0.241	0.209
Absolute kidney weight – right (g)	4.775	3.739	4.856	4.215
Relative^akidney weight – right ( %)	0.280	0.196	0.245	0.230
Absolute gonad weight – left (g)	0.178	0.119	0.172	0.185
Relative^agonad weight – left ( %)	0.010	0.006	0.009	0.010
Absolute gonad weight – right (g)	0.187	0.137	0.187	0.173
Relative^agonad weight – right ( %)	0.011	0.007	0.010	0.009

 

 

Table 2: Subacute (21-Day) dermal toxicity study in Rabbits: Gross pathological lesions

 

Pure active ingredient cyanamide (mg/kg bw/day)	0	12.5	25	37.5
Number of rabbits/group	3	3	3	3
Males:
Skin
Alopecic	0	0	1	0
Sparse fur growth	0	0	0	1
Lung
Collapsed areas	0	0	0	0
Sanguineous exudate	0	0	0	1
Petechiaeted	0	0	0	2
Small intestine
Catarrhal enteritis	0	0	0	0
Liver
Mottled	0	0	1	0
Congested	0	0	1	0
Kidneys
Medullary congestion	0	0	0	1
Cortico-medullary congestion	0	0	1	1
Cotical grey specks	0	0	0	1
Heart
Apex with petechiae	0	0	0	1
Spleen
Congested	0	0	0	0
Testes
Bulged edges on section	0	0	0	1
Females:
Skin
Alopecic	0	0	0	1
Sparse fur growth	0	0	1	2
Lung
Collapsed areas	0	0	0	1
Sanguineous exudate	0	0	0	1
Petechiaeted	0	0	0	0
Small intestine
Catarrhal enteritis	0	0	0	1
Liver
Mottled	0	0	0	0
Congested	0	0	0	1
Kidneys
Medullary congestion	0	0	0	1
Cortico-medullary congestion	0	0	0	0
Cotical grey specks	0	0	0	0
Heart
Apex with petechiae	0	0	0	0
Spleen
Congested	0	0	0	1
Ovaries
Dark spots	0	0	0	1

 

 

Table 3: Subacute (21-Day) dermal toxicity study in Rabbits: Incidences of microscopic effects

Pure active ingredient cyanamide (mg/kg bw/day)	0	12.5	25	37.5
Number of rabbits/group	3	3	3	3
Males:
Brain-Cerebrum
Microcavitations (Oedema)	0	0	1	2
Brain-Cerebellum
Microcavitations	0	0	0	1
Heart
Focal Hyalinisation of Myocardial cells	0	1	0	1
Foci of calcification	0	0	0	1
Focal haemorrhage	0	0	0	1
Small intestine
Catarrh (Jejunum)	0	0	0	0
Hyperanemia	0	0	0	1
Kidneys
Cysts	0	0	0	0
Eosinophilic material in some Convoluted tubules	0	1	0	3
Few Foci of mononuclear cells	0	0	0	1
Liver
Hyperaemia	0	0	0	0
Lungs
Focal Oedema	0	0	0	2
Atelectasis (focal)	0	0	0	0
Perivasular cuffing	0	1	0	2
Testes
Focal interstitial oedema	0	0	0	1
Females:
Brain-Cerebrum
Microcavitations (Oedema)	0	0	0	2
Brain-Cerebellum
Microcavitations	0	0	0	1
Heart
Focal Hyalinisation of Myocardial cells	0	0	0	0
Foci of calcification	0	0	0	0
Focal haemorrhage	0	0	0	0
Small intestine
Catarrh (Jejunum)	0	0	0	1
Hyperanemia	0	0	0	1
Kidneys
Cysts	0	0	0	1
Eosinophilic material in some Convoluted tubules	0	0	1	1
Few Foci of mononuclear cells	0	0	0	0
Liver
Hyperaemia	0	1	1	1
Lungs
Focal Oedema	1	0	0	1
Atelectasis (focal)	0	1	0	1
Perivasular cuffing	0	0	0	0

 

Applicant's summary and conclusion

Conclusions:

The NOAEL for dermal effects in rabbits: 25 mg/kg bw
The NOAEL for systemic effects in rabbits: 25 mg/kg bw

Executive summary:

Dormex (Hydrogen cyanamide, aqueous solution) was applied undiluted to the skin of three male and three female New Zealand White rabbits per dose level for a period of six hours per day on 5 days per week for three consecutive weeks followed by a 14 day post-application observation period. The concentrations were 0, 25, 50 and 75 mg/kg bw/day equivalent to 12.5, 25 and 37.5 mg/kg bw/day active substance Cyanamide, which were selected according to the results of a pilot study. The control group did not receive any treatment of the test substance.

There were no mortalities in any groups of the test material or post-application observation period. At the highest concentration severe erythema of the skin and reduction in the fur density around the areas of application were observed. Slight erythema during the application period were observed at the mid dose of 25 mg/kg bw/day pure active substance cyanamide which recovered one day after application. There were no significant differences in the body weight and feed consumption of animals treated with Dormex when compared to the control animals. None of the haematological, clinical chemical and urine parameters of the treated groups showed any statistical significant variation as compared to the controls at each time of measurement.

After the recovery period some organ weights revealed a statistical significance in the low, mid or high dose males. However, due to the fact that there are no consistent dose-dependent changes the findings are considered to be incidental.

The gross pathological and histopathological examinations showed no consistent findings in the low and mid dose animals. Some high dose animals showed findings even after the 14 d recovery period.

Due to the irreversibility of the local skin effects at 37.5 mg/kg bw and the reversibility of the skin findings at 25 mg/kg bw the NOAEL for dermal effects is 25 mg/kg bw of ai cyanamide in rabbits. Due to the fact that there were no systemic findings in the low and mid dose animals attributable to treatment with cyanamide the NOAEL for systemic effects was deduced at the mid dose of 25 mg/kg bw based on the histopathological findings at the high dose.