Calcium cyanamide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

10 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

22 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

1 µg/L

Assessment factor:

100

Extrapolation method:

assessment factor

PNEC marine water (intermittent releases):

2.2 µg/L

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1.09 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.151 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

For detailled description where read across is used/recommended and where it is preferrable to refain from read across, please see section 13.2 "read across justification for environmental endpoints" and "Scientific rationale for not using cyanamide as read-across substance for calcium cyanamide on toxicological endpoints"

Conclusion on classification

Acute toxicity

Invertebrates are the most sensitive species to the toxic effects of calcium cyanamide with an acute EC₅₀ of 4.2 mg calcium cyanamide/L (corresponding to 2.2 mg cyanamide/L). Based on the results obtained in the aquatic toxicity studies, calcium cyanamide does not have to be classified regarding acute toxicity to the environment.

Chronic toxicity

The acute toxicity data set of calcium cyanamide is supplemented by chronic toxicity data of the relevant transformation product cyanamide in a read-across approach (for justification for read-across for the aquatic compartment please refer to the read-across report attached to IUCLID section 13). The most sensitive chronic toxicity value was reported for reproduction of D. magna. The 21-d NOEC value of 0.1044 mg cyanamide/L obtained in this study (Murrell & Leak, 1995) corresponds to 0.199 mg calcium cyanamide/L. 

Calcium cyanamide cannot be considered as readily biodegradable based on the results obtained in a screening test (OECD 301B, CO₂ evolution test). However, higher tier testing with the relevant transformation product cyanamide resulted in DT₅₀ values for the water/sediment system of 2.5 days and 4.8 days in river and pond systems, respectively. For the water phase the corresponding DT₅₀ values were 2.3 days in rivers and 4.3 days in ponds. Elimination of [14C]-hydrogen cyanamide from the water/sediment systems occurred 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 any degradation products were detected in significant amounts.

As rapid degradation of cyanamide could clearly be demonstrated under environmentally relevant conditions in the two aerobic water/sediment model systems (see IUCLID section 5.2.2), the substance as well as the read-across partner calcium cyanamide 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.

Consequently, calcium cyanamide is classified for chronic aquatic toxicity category Chronic 3 according to Regulation (EC) No 1272/2008 (CLP).