Calcium cyanamide

Toxicity to birds

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to birds: acute oral toxicity test

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Acute oral toxicity to quails. For details see below.

GLP compliance:

no

Dose method:

gavage

Analytical monitoring:

no

Vehicle:

yes

Details on preparation and analysis of diet:

The test substance was administered by a rubber canule as a 25 % (w/v) aqueous suspension into the stomach of the quail in single doses of 5.76, 6.91, 8.29, 9.95 or 11.94 mL per kg body weight.

Test organisms (species):

Coturnix coturnix japonica

Details on test organisms:

Adult Japanese quail, 14 months old, were obtained from the Institute's colony. They were housed in groups of five, males and females separated, in wire-screen cages in a room ventilated with about 10 air changes per hour and maintained at 23 +/- 1 °C. Relative humidity was between 30 and 70 per cent, lighting was artificial with a sequence of 12 hours light, 12 hours dark. Food and tap water was freely available at all times, except for the overnight period before treatment till 4 hours after treatment, when food was withheld.

Limit test:

no

Total exposure duration (if not single dose):

0 h

Remarks:

single dose

Post exposure observation period:

14 days

No. of animals per sex per dose and/or stage:

For each dose five males and five females were used.

Control animals:

not specified

Nominal and measured doses / concentrations:

nominal concentrations: 1440, 1728, 2073, 2488 and 2985 mg/kg bw
no measured concentrations.

Details on test conditions:

no further details given.

Details on examinations and observations:

After treatment the birds were observed frequently for signs of intoxication during the first 4 post-treatment hours and thereafter at least once daily throughout a 14-day observation period.

Details on reproductive parameters:

no reproduction study

Reference substance (positive control):

no

Key result

Dose descriptor:

LD50

Effect level:

ca. 1 665 mg/kg bw/day (nominal)

Conc. / dose based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% CL: 1575 to 1763 mg/kg bw

Repellency factors (if applicable):

not applicable

Mortality and sub-lethal effects:

Clinical observations during the first 4 post-treatment hours revealed sluggishness and slight diarrhoea. Later on coma was frequently observed and preceded death. Most of the deaths occurred between 3 and 20 h after treatment. One cock died on the fifth post-treatment day. Thereafter the survivors recovered gradually and looked quite healthy again at the end of the observation period. The individual body weights indicated retarded growth or weight loss in the first post-treatment week. Macroscopic examination of the survivors at autopsy did not reveal any treatment-related gross alteration.

Effects on reproduction:

no reproduction study

Results with reference substance (positive control):

no reference substance

Further details on results:

no further details on result.

Reported statistics and error estimates:

From the mortality figures the oral LD50 of Perlka in Japanese quail was calculated to be 1665 mg/kg bw with 1575 and 1763 as the 95% confidence limits.

Validity criteria fulfilled:

yes

Conclusions:

From the mortality figures the oral LD50 of Perlka in Japanese quail was calculated to be 1665 mg/kg body weight of Perlka with 1575 mg/kg and 1763 mg/kg as the 95% confidence limits. This is equal to 703 mg/kg calcium cyanamide.

Executive summary:

The acute oral toxicity of Perlka (containing about 42.2% calcium cyanamide) to 14 months-old Japanese quail (Coturnix coturnix japonica) was assessed after a single dose and a 14-day observation period. Test material was administered to 5 birds per dose and sex by gavage as a 25% v/v aqueous suspension at 5.76, 6.91, 8.29, 9.95 and 11.94 mL/kg (equivalent to 1440, 1728, 2073, 2488 and 2985 mg Perlka/kg body weight).

Clinical observations during the first 4 post-treatment hours revealed sluggishness and slight diarrhoea. Most of the deaths occurred between 3 and 20 h after treatment. One cock died on the fifth post-treatment day. Thereafter the survivors recovered gradually and looked quite healthy again at the end of the observation period. The individual body weights indicated retarded growth or weight loss in the first post-treatment week macroscopic examination of the survivors at autopsy did not reveal any treatment-related gross alteration.

From the mortality figures the oral LD50 of Perlka in Japanese quail was calculated to be 1665 mg/kg body weight of Perlka with 1575 mg/kg and 1763 mg/kg as the 95% confidence limits. This is equal to 703 mg/kg calcium cyanamide.

 

Results Synopsis:

 

Test Organism Size/Age (mean weight): males 131.2 g, females 160.4 g, 14 months old

 

LD50: 1665 mg/kg bw, 95% C.I.: 1575 to 1763 mg/kg bw (Perlka), which is equal to 703 mg/kg calcium cyanamide.

Endpoint(s) Effected: clinical signs, body weight loss and mortality

Description of key information

The toxicity of calcium cyanamide as well as its transformation product cyanamide to birds was investigated in different studies.

A summary of the avian toxicity endpoints is provided in the following table:

Species	Test	Measurement endpoint	Endpoint value
			Test substance	Active ingredient
Japanese quail	Acute toxicity	LD50	1665 mg test substance/kg bw	703 mg pure calcium cyanamide/kg bw
Bobwhite quail (Colinus virginianus)	Single oral dose	LD50	-	350 mg pure cyanamide/kg bw
Mallard duck (Anas platyrhynchos)	Short-term dietary (5-day)	LC50	-	>5000 ppm pure cyanamide
Bobwhite quail (Colinus virginianus)	Short-term dietary (5-day)	LC50	-	>5000 ppm pure cyanamide
Bobwhite quail (Colinus virginianus)	Reproductive toxicity (22 weeks)	NOEC	300 mg test substance/kg bw	152 mg pure cyanamide/kg bw

 

In conclusion, these data indicate a low toxicity of calcium cyanamide or its degradation product cyanamide to birds.

Please note, however, that for the environmental endpoint ‘Toxicity to birds’, cyanamide is not considered a suitable read-across partner for calcium cyanamide. This conclusion is drawn based on the composition and on the comparison of toxicological studies from endpoints, where experimental results are available for both compounds, calcium cyanamide and cyanamide.

Calcium cyanamide consists of approx. 50% (w/w) calcium. In aqueous solution, Ca²⁺ ions are released, and CN₂ transforms into hydrogen cyanamide (H₂CN₂) with hydrogen being covalently bound to the CN₂ moiety. Dissolution kinetics, including dependency on the aqueous milieu, is difficult to predict for calcium cyanamide. In addition, cyanamide is not hydrolytically stable under acidic conditions (< pH 2). Thus, cyanamide will degrade to urea in the stomach of birds. Because of the complex composition of calcium cyanamide technical grade compared to cyanamide, the kinetics of the release of cyanamide from calcium cyanamide and the subsequent degradation to urea is difficult to extrapolate and adds to the overall uncertainty when it comes to read across. Therefore, even though cyanamide will be released from calcium cyanamide, the appropriateness of using cyanamide data for extrapolation adverse effects needs to be based on a case by case decision. It is not a default assumption.

The differences between cyanamide and calcium cyanamide are pronounced for any test where classification is based on a limit dose, or for in vitro tests, where test systems are generally sensitive to pH shifts and osmolarity, or for any test with oral application (i.e. toxicity studies with birds). In the latter case, dissolution kinetics will determine if the compound is already resorbed in the oral cavity (i.e. in feeding studies), in the stomach, or not until it reaches the intestines. Dissolution kinetics also determines if and at what speed cyanamide is released from calcium cyanamide. A delayed release will lead to lower systemic concentrations that may not exceed the metabolic capacities of protective pathways or repair mechanisms, compared to a bolus effect that might occur after application of cyanamide.

This line of argumentation is supported by differences in experimental results from calcium cyanamide versus cyanamide studies. For example, in acute oral toxicity studies in rat, the LD50 for “calcium cyanamide 20.5%N” is calculated to be 765 mg/kg bw (de Groot, 1976), which is equal to 639 mg/kg calcium cyanamide, technical grade (Kalkstickstoff) or approx. 270 mg/kg cyanamide. In contrast, the acute oral LD50 of pure active substance cyanamide in rats was estimated to be 142 mg/kg bw for the sexes combined (Engel, 1973). Another example is the result of the pre-natal developmental toxicity studies according to OECD 414, in rat. Here, the study on cyanamide leads to a classification as Repro 2 (s. RAC opinion, CLH-O-0000001412-86-67/F, from 5.6.2015, based on diaphragmatic hernias reported in Morseth (1989)), while a comparable study with calcium cyanamide was clearly negative [WIL Research Europe-Lyon, 2014].”

For further details and a comprehensive justification against read-across please refer to chapter 13.2, report title “Scientific rational for not using cyanamide as read-across substance for calcium cyanamide on toxicological endpoints."

Due to the low toxicity of calcium cyanamide to Japanese quail, and the feed avoidance behaviour (see Korn,1990 in IUCLID section 6.6), additional toxicity studies (including chronic) for birds are not required (especially if during application the granulated product was incorporated into the soil).

Key value for chemical safety assessment

Short-term EC50 or LC50 for birds:

703 mg/kg food