Cyanamide

Endpoint summary

Description of key information

The substance was concluded to be "readily biodegradable".

Additional information

Two studies examined the ready biodegradation of cyanamide in a nutrient medium inoculated with activated sludge. The result of the study of van der Hoeck showed that cyanamide can be regarded as not ready biodegradable by the terms of this test. A following study (Malta, 1990) showed that cyanamide was completely degraded within two weeks when it served as nitrogen source for degradation of a carbon-containing compound (sodium acetate), whereas the cyanamide degradation was rather slow when cyanamide served as both carbon and nitrogen source.

It can be concluded that the biodegradation of cyanamide in a standard ready biodegradability test is prevented by the presence of another easily available nitrogen source.

 

In two water/sediment systems, DT50 values of 2.5 days (river) and 4.8 days (pond) for the whole systems and half-lives of 2.3 days (river) and 4.3 days (pond) for the water phase were calculated. elimination of [14C]-cyanamide from the water/sediment systems proceeded mainly via mineralisation to CO2. Only one major metabolite, identified as urea, was detected in the Pond system. For urea DT50 values of 2.9 days (river) and 7.6 days (pond) for the whole systems and half-lives of 2.7 days (river) and 7.5 days (pond) for the water phase were calculated. In the sediments, neither the parent substance nor degradation products were detected in significant amounts.

 

As rapid degradation of cyanamide could clearly be demonstrated under these environmentally realistic conditions in the two aerobic water/sediment model systems (see IUCLID section 5.2.2), the substance can thus be considered as rapidly degradable according to the CLP Regulation (EC) No 1272/2008, Annex I sections 4.1.2.9.2 and 4.1.2.9.3 and therefore cyanamide was concluded to be "readily biodegradable".

 

Reliable information on the biodegradation of cyanamide in soil is available. The following DT50 and DT90 values were calculated for the aerobic and anaerobic degradation of cyanamide in soil under laboratory conditions.

DT50 aerobic : 0.7 days – 4.6 days
DT90 aerobic: 2.4 – 15.2 days
DT50 anaerobic: 34.7 days
DT90 anaerobic: 105 days

The degradation of Cyanamide under aerobic and anaerobic conditions was assessed in a GLP-compliant guideline study by Schmidt, 1990; Schmidt, 1991).

Under aerobic conditions, the primary aerobic pathway by which the parent compound disappeared from soil was the final degradation to [14CO2] (complete mineralization). This fraction accounted for approximately 94.6 % of applied radioactivity after 14 days. The half-life of cyanamide was calculated using a first order kinetic and was found to be 1.26 days. The calculated time to 90 % degradation was 1.94 days. One minor degradation product was identified as dicyandiamide accounting for 0.431 % of applied radioactivity at maximum.

Under anaerobic conditions, the degradation was slower (DT50anaerobic = 34.7 days), and mineralization did not occur to the same extent as under aerobic conditions. Four minor degradation products occurred and were identified as dicyandiamide, guanylurea, guanidine and urea. None of the degradation products exceeded the trigger value of 10 % of applied radioactivity. Guanylurea was found with 7.5 % of TAR at maximum value.

In a study of Heß (1978) the DT50 values of cyanamide ranged from 1 to 3 days in two loamy sand soils with different organic carbon content and from 6-12 days in a sand soil with a very low organic carbon content. The results show that the degradation of cyanamide in soil is influenced by the organic carbon content indicating that the biotic degradation prevails in soils. Furthermore, the degradation rate of cyanamide in the test soils depended on the application rate with a faster degradation observed in the test soils receiving the lowest application rate.

Additionally, information on the transformation and fate of Calcium cyanamide in soil matrices is available. It was demonstrated that upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide. Thus, for industrial manufacture and use, release of calcium cyanamide to water will result in potential environmental exposure of hydrogen cyanamide. Any subsequent potential soil exposure via sludge and air will be by cyanamide, not calcium cyanamide.

The transformation from cyanamide to secondary transformation products depended on the tested material. Whereas for Cyanamid F1000 only urea and ammonia in larger amounts could be detected, for PERLKA also nitrate and DCD were determined. The observed nitrate is not a transformation product but represents the original amount of nitrate in PERLKA.

The normalised DT50 value of 0.78 days at 20°C (Klein et al., 2019) is used for the risk assessment according to Regulation (EC) No 1907/2006 (REACH). It is concluded that Cyanamide is rapidly degraded in soil and that there is hence no indication for persistency regarding this environmental compartment.