Cyanamide

Endpoint summary

Description of key information

Toxicity to soil macroorganisms except arthropods:

The acute toxicity effects of cyanamide (SKW Cyanamid L500 + AHL (synonymous to urea ammonium nitrate) on earthwarms (Eisenia fetida) were tested in a 14-day laboratory study. The LC50 observed after 14 days of incubation was > 111.3 mg test substance/kg dry soil (active substance cyanamide), the highest rate tested.

The long-term toxicity effects of cyanamide (50 % aqueous solution) on earthworms were tested in the earthrowm reproduction test according to OECD guideline 222 (Scheffczyk, 2016). The purpose of this study was to determine a NOEC/LOEC and if possible, an EC10, EC20 and EC50 value for reproduction (56 days after application) and a NOEC/LOEC value for mortality and the biomass development (28 days after application) of the earthworm Eisenia fetida (Lumbricidae) using a standard LUFA 2.2 soil. The test item was mixed with the substrate. The earthworm Eisenia fetida (Lumbricidae) was chosen as a representative of the soil fauna. Biomass, mortality and reproduction were not affected by the treatment. Therefore, the NOEC for biomass (28 d), mortality (28 d) and reproduction (56 d) was determined to be ≥ 1.05 mg a.s./kg soil (dw), the highest dos tested. This value was not considered relevant for chemical safety assessment, for justification please refer to the field“ Additional information”.

Toxicity to terrestrial arthropods:

Cyanamide tested under worst-case laboratory conditions as an aqueous solution of cyanamide (50-51.6% (w/w) aqueous solution of cyanamide) on honey bees and other beneficial arthropods proved to be harmful to bees, Aphidius rhopalosiphi, Pardosa spec., Chrysoperla carnea, Aleochara bilineata and harmless to Poecilus cupreus. In dose-response tests with Typhlodromus pyri and Aphidius rhopalosiphi, the lowest LR50 values obtained were determined to be 445.6 g pure cyanamide/ha and 432.1 g pure cyanamide/ha, respectively. In an extended laboratory test (aged residues) with Aleochara bilineata it was classified as harmless according to the IOBC hazard rating scheme. In a dose-response test with the collembolan species Folsomia candida, the EC10 for reproduction was determined to be 1.515 mg pure cyanamide/ka soil dw.

The corresponding toxicity endpoint values are summarised in the following table:

Species	Test	Measurement endpoint	Endpoint value
Apis mellifera	Oral contact (overspray with 0.2 L product/L)	LD50	<51.6 µg pure cyanamide/bee Abnormal behaviour and mortality
Aphidius rhopalosiphi	acute laboratory test	mortality	100 %
Aphidius rhopalosiphi	dose-response test	mortality	LR50= 0.432 kg pure cyanamide/ha
Aphidius rhopalosiphi	dose-response test	mortality	LR50= 0.620 kg pure cyanamide/ha
Chrysoperla carnea	acute laboratory test	mortality	92 %
Chrysoperla carnea	dose-response test	mortality	LR50= 3.4 kg pure cyanamide/ha
Aleochara bilineata	dose-response test	reproduction	ER50= 0.93 kg pure cyanamide/ha
Aleochara bilineata	acute laboratory test	reproduction	99.7 %
Aleochara bilineata	extended laboratory test	reduction of reproduction	15.6 %
Poecilus cupreus	acute laboratory test	mortality/reduction of feeding rate	1.4 %
Pardosa spec.	acute laboratory test	mortality/reduction of feeding rate	100 %
Pardosa spec.	dose-response test	mortality	LR50= 2.1 kg pure cyanamide/ha
Typholodromus pyri	dose-response test	mortality	LR50= 0.446 kg pure cyanamide/ha
Typholodromus pyri	dose-response test	mortality	LR50= 2.07 kg pure cyanamide/ha
Folsomia candida	dose-response test	reproduction	EC10=1.515 mg pure cyanamide/kg soil dw

Toxicity to terrestrial plants:

Two non-target terrestrial plant studies were conducted with cyanamide (a 50.6 % (w/w) aqueous solution of cyanamide). In a seedling emergence Tier 2 (LR50) test (performed according to the OPPTS 850.4225 (1996)) , 9 common plant specie were evaluated the following applied dose levels: 0.125, 0.5, 2.0, 8.0 and 32.0 kg Cyanamid L500/ha, corresponding to 0.063, 0.253, 1.01, 4.05 and 16.19 kg as/ha. Effects on seedling emergence and early growth following soil surface application were assessed. The most sensitive endpoint in this study was shoot dry weight. The most sensitive plant was Allium cepa with an EC50 value of 1.722 kg Cyanamid L500/ha when applied directly to the soil (corresponds to 0.87 kg as/ha).

In a in a vegetative vigour Tier 2 (LR50) test (performed according to the OPPTS 850.4220), the most sensitive endpoint was dhoot dry weight for all species. The most sensitive sensitive species tested was tomato (Lycopersicon esculentum). The EC50 value for tomato was determined as 33.2 kg Cyanamid L500/ha.

A long-term test according to ISO 22030 (2005): "Soil Quality – Biological methods – Chronic Toxicity in Higher Plants" was performed with Avena sativa (Oat, Monocots) and Brassica rapa (turnip, Dicots). For A. sativa, the lowest NOEC was 50 mg a.s./kg soil dw (increase of shoot fresh mass on day 14 and day 39). The lowest NOEC for B. rapa was 50 mg a.s./kg soil dw (increase of shoot fresh weight on day 14 and dry weight on day 28). Due to a lack of a dose-response relationship between the test item concentrations and the observed effects on the respective endpoints, ECx values could not be calculated. The EC50, however, can nevertheless to be deduced to be > 100 mg a.s./kg soil dry mass. The test item did not reduce the biomass or number of inflorescences or seed pods at any of the tested concentrations up to and including 100 mg a.s./kg soil dry mass for any of the two test species, B. rapa and A. sativa. Based on the assumption that only a reduction in biomass or number of flowers/seed pods is an ecological adverse effect, the no observed adverse effect concentration (NOAEC) derived from the chronic plant test is ≥ 100 mg a.s./kg soil dry mass.

Toxicity to soil microorganisms:

From the results of two soil microflora tests (soil respiration test and nitrogen transformation) performed in two available studies, it can be concluded that the use of Cyanamide 49% or 51.1% (w/w) aqueous solution of cyanamide in a dose rate equivalent to around 20 kg ai/ha and the 5-fold thereof (100 kg ai/ha)) is safe for soil non-target microorganism as the results of both tests in both studies were practically not higher than 25% of the control.

Toxicity to birds:

The toxicity of cyanamide (49-50% (w/w) aqueous solution of cyanamide) to birds was examined in four available studies: an acute toxicity study (in Bobwhite Quail), two short-term toxicity studies (in Bobwhite Quail and Mallard Duck) and one sub-chronic and reproduction study (Bobwhite Quail). The LD50 value for the Bobwhite Quail was determined to be 350 mg/kg bw. Despite the slight acute toxicity cyanamide, the feeding studies resulted in less critical NOEC and LC50 values in feed. In both of these short-term dietary toxicity studies the LC50 values were determined to be >5000 mg/kg feed (Bobwhite Quail) and >5000 mg/kg feed (Mallard Duck), thus, the repeated uptake (5 days) did not result in higher toxicity when compared to a single acute dose. In the reproduction toxicity study a NOEC value of 152 mg/kg feed, corresponding to 13.3 mg ai/kg bw/d (Bobwhite Quail) was determined based on a reduction of chick 14-day body weights at 506 mg ai/kg diet (ppm), which was the only observed substance-related effect. It can be stated that cyanamide is of low acute toxicity to birds, producing no mortality at the maximum dose levels used in short term dietary tests.

Additional information

Justification for chosing the EC10 of 1.515 mg cynamide/kg soil (dw) for the reproduction of F. candida (Moser 2009) as key value for chemical safety assessment

The study conducted by Scheffczyk (2016) investigates the 56-d reproduction toxicity of cyanamide in earthworm (Eisenia fetida) in accordance with OECD guideline 222 and ISO 11268-2. In the first step a 28-d range-finding study (non-GLP) was conducted at 0 (control), 0.1, 1, 10, 100 and 100 mg cyanamide/kg soil (dw) in two replicates. Based on the dose-response relationship observed in the range-finding study, the concentration range for the definitive test (GLP) was chosen as follows: 0 (control), 0.017, 0.031, 0.056, 0.10 mg, 0.18, 0.32, 0.58, and 1.05 mg cyanamide/kg soil (dw).

In the definitive test, no adverse effects could be observed at the highest concentration evaluated in the test. Thus, the NOEC from this study was determined to be ≥ 1.05 mg cyanamide/kg soil dw, a definitive LOEC value could not be derived.Although the validity criteria of OECD guideline 222 are met (mortality in control ≤ 10 %; number of juveniles per control replicate ≥ 30; coefficient of variation for the number of juveniles in control ≤ 30 %), the variability between replicates in the control and in samples of all test concentrations is relatively high, thus reducing the robustness of the data.

In accordance with the ECHA Guidance on information requirements and chemical safety assessment, Chapter R.10: Characterisation of dose [concentration]-response for environment (May 2008, p. 11), the NOEC is defined as “the highest concentration tested at which the substance is observed to have no statistically significant effect (p<0.05) when compared with the control, within a stated exposure period” (OECD 211, 1998b) or the test concentration immediately below the LOEC, which when compared with the control has no statistically significant effect (p<0.05) within a stated period (OECD 211, 1998b).” Furthermore, “[t]here has to be a concentration-effect relationship.” However, in the present main test by Scheffczyk (2016), no concentration-effect relationship was observed.Any bounded NOEC of cyanamide for the reproduction of E. fetida under the conditions of OECD guideline 222 would presumably be higher than the highest test concentration chosen is the test by Scheffczyk (2016). However, such a bounded NOEC value is currently not available and could only be determined by repeat testing.  

The most sensitive bounded NOEC value that is currently available is reported for collembola (Folsomia candida). The study by Moser (2009) investigates the long-term toxic effects on the reproduction of F. candida after 28-d exposure in artificial soil spiked with cyanamide at 0.4, 1.26, 4.00, 12.46, 40.00, 60.00, 80.00, 100.00 mg a.s./kg soil (dw). This GLP guideline study (ISO 11267) reports a clear dose-response relationship with a significant reduction of the number of juveniles in comparison to the control at 1.26 mg cyanamide/kg sol (dw), resulting in a NOEC and EC10 of 0.4 and 1.515 mg cyanamide/kg soil (dw), respectively. 
In accordance with the ECHA Guidance on information requirements and chemical safety assessment, Chapter R.10:  Characterisation of dose [concentration]-response for environment (May 2008, p. 11), EC10 values for long-term test which are obtained using an appropriate statistical method will be used preferentially. Therefore, the EC10 of 1.515 mg cynamide/kg soil (dw) is considered the key value for chemical safety assessment.
Please note: The EC10 of 1.515 mg cynamide/kg soil (dw) has been recalculated by the German Competent Authority (UBA) and was used for the calculation of the PNECsoil in the Assessment Report for the evaluation of cyanamide as active biocidal substance (July 2016;http://dissemination.echa.europa.eu/Biocides/ActiveSubstances/1280-03/1280-03_Assessment_Report.pdf).

In conclusion, the unbounded NOEC of ≥ 1.05 mg cyanamide/kg soil (dw) in E. fetida reported by Scheffcyzk (2016) is not considered relevant for hazard assessment purposes. Instead, the EC10 of 1.515 mg cyanamide/kg soil (dw)for the reproduction of F. candida (Moser 2009) is considered the key value.