Cyanamide

Endpoint summary

Description of key information

Toxicity to fish

In a short-term toxicity test in fish an EC50 of 43.1 as mg/L and a NOEC of 30.6 mg as/L were obtained with Bluegill sunfish (lepomis macrochirus) fish.

In a long-term toxicity test with fish (Rainbow trout (Oncorhynchus mykiss)) the calculated LC50 was 11.8 mg of pure active ingredient /L and the NOEC was 3.7 mg ai/L. 

Toxicity to aquatic invertebrates (daphnia magna)

In a static, short-term (48 hours) test with daphnia magna the calculated EC50 was 3.2 mg of pure active ingredient (ai)/L, the NOEC was calculated to be 1.6 mg ai/L and the LC50 was calculated to be 4.3 mg ai/L.

In a long-term toxicity test with Daphnia magna in an EC50 of > 0.41 mg/L and a NOEC of 0.1044 mg /L were calculated from the obtained results.

Toxicity to aquatic algae and cyanobacteria

Growth inhibition data obtained with the 51.1 % (w/w) aqueous solution of cyanamide on Pseudokirchneriella subcapitata were as follows: For biomass, the 96-hour EbC50 was 13.2 mg of the 51.1 % (w/w) aqueous solution of cyanamide/L (6.7 mg as/L) with a corresponding NOEC of 5.0 mg of the 51.1 % (w/w) aqueous solution of cyanamide/L (2.6 mg as/L). Considering the growth rate the following data were obtained: The 96-hour ErC50 was 32.5 mg of the 51.1 % (w/w) aqueous solution of cyanamide/L (16.6 mg as/L) with a corresponding NOEC of 5.0 mg of the 51.1 % (w/w) aqueous solution of cyanamide/L (2.6 mg as/L).

Toxicity to aquatic plants other than algae

The effects of cyanamide were investigated in Lemna gibba G3 in a 7 day test. The calculated endpoint values were as follows: 7 day EC50 (dry weight) = 2.4 mg ai/L and a corresponding NOEC = 0.5 mg ai/L, a 7 day EC50 (biomass) = 2.33 mg ai/L and a corresponding NOEC = 0.5 mg ai/L, a EC50 (growth rate) = 5.61 mg ai/L and a corresponding NOEC = 0.5 mg ai/L.

Toxicity to microorganisms

In Pseudomonas putida the toxicity threshold (19 hours) was found to be 157 mg ai/L. The EC50 (19 hours) 283 mg as/L. The NOEC was determined to be 180 mg product/L, corresponding to 88 mg as/L.

Toxicity to other aquatic organisms

The effect of a 51 % (w/w) aqueous solution of cyanamide on sediment dwelling organisms: Chironomus riparius was determined in an aerated, 28-day emergence test. The ecotoxicological endpoints for Chironomus riparius for the 51 % (w/w) aqueous solution of cyanamide were as follows: Emergence inhibition: EC50 (28d) = 56.7 mg of a 51 % (w/w) aqueous solution of cyanamide/L (28.97 mg ai/L) and an emergence ratio NOEC (28d) = 36.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (18.39 mg ai/L) LOEC (28d) = 60.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (30.66 mg ai/L) Development rate: NOEC (28d) = 13.0 mg .of a 51 % (w/w) aqueous solution of cyanamide/L (6.64 mg ai/L) and LOEC (28d) = 22.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (11.24 mg ai/L).

Additional information

Acute studies indicate that cyanamide has a low toxicity to fish, a moderate toxicity to algae and a high toxicity to daphnids (EC50 (48 h) = 3.2 ai mg/L). The EC₅₀-values of the short and long - term toxicity are in a range between 0.4 and 180.0 mg of an aqueous solution of cyanamide/L (equivalent to 0.2 to 90.0 mg of the pure ai/L). The NOECs of the chronic studies indicate that daphnids are the most susceptible species, with a NOEC of 0.1044 mg cyanamide/L (mean measured concentration).

In the following, a summary of the aquatic toxicity testing values obtained with the aqueous solution of cyanamide and extrapolated to pure active ingredient/substance cyanamide

Species	Test/duration	NOEC mg/L^1	EC50 or LC50 mg/L^1	Reference
Oncorhynchus mykiss (fish)	acute (96 h)	62.5 [30.6]^2	180.0 [83.2]^2	McAllister et al. (1985)
Oncorhynchus mykiss (fish)	acute (96 h)	64.8 [31.8]^2	93.0 [45.6]^2	Barrows, B. (1985),
Bluegill sunfish (fish)	acute (96 h)	62.5 [30.6]^2	88.0 [43.1]^2	McAllister et al. (1985)
Cyprinus carpio (fish)	acute (96 h)	61.0 [29.9]^2	165.0 [80.9]^2	Bowmann, J. (1990)
Daphnia magna (invertebrates)	acute (48 h)	3.2 [1.6]^2	6.5 [3.2]^2	Adema, M. (1983)
Oncorhynchus mykiss (fish)	chronic (21 d)	7.5 [3.7]^2	24.0 [11.8]^2	Bowmann, J. (1990)
Daphnia magna (invertebrates)	chronic (21 d)	0.1044 [0.1]^2	> 0.41 [0.2]^2	Murell et al. (1995)
Pseudokirchneriella subcapitata (algae)	acute (90.5 h)	2.2 [1.1]^2	27.5 [13.5]^2	Schoot Uiterkamp, A.J.M. (1988)
Pseudokirchneriella subcapitata (algae)	acute (96 h)	5.0 [2.6]^2	13.2 [6.7]^2	Seyfried, B. (2000)
Anabaena flos-aquae (cyanobacteria)	acute (72 h)	0.1 [0.05]^2	1.29 [0.65]^2	Hertl, J. (2000)
Chironomus riparius (insects)	chronic (28 d)	13.0 [6.6]^2	56.7 [28.9]^2	Heintze, A. (2001)
Lemna gibba (plant)	Short-term (7 d)	1.0 [0.5]^2	4.6 [2.4]^2	Hertl, J. (2000)
Pseudomonas putida (microorganism)	Acute (19 h)	Toxicity threshold: 320 [157]^2	577 [283]^2	Hanstveit et al. (1988)

¹= based on an aqueous solution of Cyanamide (about 50%)

²= based on pure active ingredient

Invertebrates are the most sensitive species to the toxic effects of cyanamide with an acute EC50 of 3.2 mg/L. Tests with blue-green algae show even lower EC50 values below 1 mg/L. These results were not regarded as relevant for classification and labeling as this test has significant deficiencies and other test with the more relevant green algae species in several tests confirmed EC50 values of higher than 10 mg/L.

As cyanamide is regarded ready biodegradable the substance has to be to be classified regarding as chronic env. tox. cat. 3 (H412 Harmful to aquatic life with long-lasting effects) according to CLP (GHS) based on the available long-term studies. This classification is in accordance with the conclusion of the 33 RAC-Meeting (1 -5 June 2015, Helsinki).