Calcium cyanamide

Toxicity to other aquatic organisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to other aquatic vertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000-12-21 until 2001-06-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Streloke & Köpp (1995): Long-term toxicity test with Chironomus riparius: Development and validation of a new test system.

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Draft OECD 219 (Feb. 2000)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The concentration of cyanamide in overlying water, sediment pore water and wet sediment was determined 0, 7 and 28 days after application.

Vehicle:

no

Test organisms (species):

other: Chironomus riparius

Details on test organisms:

25 larvae of the first larval stage (2 - 3 days old)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Post exposure observation period:

No post exposure observation period

Hardness:

Water used throughout the study was Elendt M4 Medium (high-hardness media)

Test temperature:

Not indicated

pH:

pH 6.0

Dissolved oxygen:

Not indicated

Salinity:

Freshwater

Nominal and measured concentrations:

Treatments consisted of a water control, 3.0, 5.0, 8.0, 13.0, 22.0, 36.0, 60.0 and 100.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L, corresponding to 1.53, 2.56, 4.1, 6.64, 11.24, 18.4, 30.66 and 51.1 mg as/L.
Mean measured concentrations of cyanamide in overlying water at day 0 were 1.75, 13.8 and 46.2 mg/L for the test vessels of 3.0, 22.0 and 100.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L, corresponding to 0.89, 7.05 and 23.60 mg ai/L and ranged from 89 to 125 % of nominal concentrations.
Mean measured concentrations of cyanamide in pore water at day 0 were 0.59, 1.75 and 1.74 mg/L for the test vessels of 3.0, 22.0 and 100.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L in the water phase and ranged from 3 to 45 % of nominal concentrations. This values correspond to 0.30, 0.89 and 0.88 mg ai/L.
Mean measured concentrations of cyanamide in sediment at day 0 were below the limit of quantification (LOQ = 0.411 mg/kg) for the test vessels of 3.0 and 22.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L in the water-phase and 1.0 mg/kg for the highest test concentration level.

Details on test conditions:

The test organisms were fed during the study and the study was conducted under static conditions. Artificial sediment that consisted of 10 % sphagnum peat, 20 % kaolin clay and 70 % industrial sand and adjusted to pH 6.0 was used as a substrate. Water used throughout the study was Elendt M4 Medium. Test vessels (2 L glass-beakers) containing a 2 cm layer of sediment and 15 cm of overlying water were prepared and allowed to acclimate 7 days before use. 25 larvae of the first larval stage (2 - 3 days old) were added to each vessel 24 hours prior to treatment.
Four replicates were used for each treatment. At test start, the aqueous solution of Cyanamide was applied just below the water surface of the test vessels by using a pipette and gently mixed without disturbing the sediment.

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

28.97 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

18.39 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

30.66 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

6.64 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: development rate

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

11.24 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: development rate

Details on results:

After 28 days, the emergence in the water control was 87 %. The emergence was not significantly inhibited up to 36.0 mg of the 51 % aqueous solution of cyanamide/L. At the highest test concentration the inhibition of emergence was 98 %. The calculated emergence ratio was not significantly reduced at treatment concentrations at or below 36.0 mg of the 51 % aqueous solution of cyanamide/L.
The development rate as an indicator of an emergence delay was not significantly reduced at treatment concentrations of 13.0 mg of the 51 % aqueous solution of cyanamide/L and below. Only one of the test vessels of the 22.0 mg/L test concentration level indicate a significant difference in number of male to number of female. Due to the fact that at higher test concentrations no respective effect was observed, no concentration effect relationship was found. Therefore, the calculation of the toxicological endpoints was performed with the pooled number of male and female midges.

Results with reference substance (positive control):

No positive control

Reported statistics and error estimates:

Not indicated

Analysis of cyanamide in overlying water

The results indicated that cyanamide decreased with time in the overlying water for the test vessels of 3.0 and 22.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L. After 7 days only about the half of the initial concentration was found. After 28 days the cyanamide concentration was found below the limit of quantification. For the highest concentration level the decrease started after the 7th day of exposure and even at 28th day of exposure cyanamide was found above the limit of quantification. The active substance cyanamide was degraded to 3.3 % of the initial nominal concentration at the highest test concentration and to less than 1 % of the initial nominal concentration at the lower concentration levels.

Analysis of cyanamide in pore water

With a latency of 7 days at the highest concentration level the results indicated that cyanamide decreased with time in the pore water.

Analysis of cyanamide in sediment

Less than 0.5 % of cyanamide was transferred to the sediment.

Analytical determination of concentrations tested in the water phase:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean measured test concentrations (mg/L) of samples taken after
	0 d	7 d	28 d
Water control	< LOQ	< LOQ	< LOQ
3.0	1.75	0.69	< LOQ
22.0	13.8	8.20	< LOQ
100.0	46.2	57.7	1.0

LOQ = 0.154 mg/L

Analytical determination of concentrations tested in the pore water:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean measured test concentrations (mg/L) of samples taken after
	0 d	7 d	28 d
Water control	< LOQ	< LOQ	< LOQ
3.0	0.59	< LOQ	< LOQ
22.0	1.75	0.65	< LOQ
100.0	1.74	5.07	< LOQ

LOQ = 0.154 mg/L

Analytical determination of concentrations tested in the sediment:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean measured test concentrations                                                               (mg/kg)                                of samples taken after
	0 d	7 d	28 d
Water control	< LOQ	< LOQ	< LOQ
3.0	< LOQ	< LOQ	< LOQ
22.0	< LOQ	< LOQ	< LOQ
100.0	1.0	< LOQ	< LOQ

LOQ = 0.154 mg/L

Summary of emergence data of Chironomus ripariusto a 51 % (w/w) aqueous solution of cyanamide for 28 days:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean emergence (%)	Mean development rate (%)	Males – number of emerging adults	Females – number of emerging adults
Water control	87.0	0.0629	40	47
3.0	84.0	0.0646	38	46
5.0	98.0	0.0608	38	61
8.0	78.0	0.0643	36	42
13.0	85.0	0.0624	48	40
22.0	96.0	0.0562	27	69
36.0	84.0	0.0550	36	48
60.0	37.0	0.0502	19	18
100.0	2.0	0.0457	1	1

No chironomids emerged before day 14

Validity criteria fulfilled:

yes

Conclusions:

*Emergence inhibition:
EC50 (28d) = 56.7 mg of a 51 % (w/w) aqueous solution of cyanamide/L (28.97 mg ai/L)

*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)
LOEC (28d) = 22.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (11.24 mg ai/L)

*Based on nominal initial overlying water concentrations).

Executive summary:

The effect of a 51 % (w/w) aqueous solution of cyanamide on Chironomus riparius was determined in an aerated, 28-day emergence test which was conducted in a similar way to the OECD 219. 25 larvae of the first larval stage (2 - 3 days old) were added to each vessel 24 hours prior to treatment. Treatments consisted of a water control, 3.0, 5.0, 8.0, 13.0, 22.0, 36.0, 60.0 and 100.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L, corresponding to 1.53, 2.56, 4.1, 6.64, 11.24, 18.4, 30.66 and 51.1 mg as/L. Four replicates were used for each treatment. Analysis of cyanamide was performed in overlying water, in pore water and in sediment. After 28 days, the emergence in the water control was 87 %. The emergence was not significantly inhibited up to 36.0 mg of the 51 % aqueous solution of cyanamide/L. At the highest test concentration the inhibition of emergence was 98 %. The calculated emergence ratio was not significantly reduced at treatment concentrations at or below 36.0 mg of the 51 % aqueous solution of cyanamide/L. The development rate as an indicator of an emergence delay was not significantly reduced at treatment concentrations of 13.0 mg of the 51 % aqueous solution of cyanamide/L and below. Only one of the test vessels of the 22.0 mg/L test concentration level indicate a significant difference in number of male to number of female. Due to the fact that at higher test concentrations no respective effect was observed, no concentration effect relationship was found. Therefore, the calculation of the toxicological endpoints was performed with the pooled number of male and female midges.

Based on nominal initial overlying water concentrations, 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) and 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), LOEC (28d) = 22.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (11.24 mg ai/L).

Reference 2

Endpoint:

toxicity to other aquatic vertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide.
Therefore, ecotoxicity in natural aquatic environments can be expressed in terms of cyanamide, irrespective of the substance constituting the exposure source. This is supported by experimental results: After stoichiometric correction of test concentrations, toxic effect values of cyanamide and calcium cyanamide are very similar in all standard test organisms. Thus, read-across from cyanamide to calcium cyanamide is justified for aquatic environmental endpoints.
For agricultural applications, calcium cyanamide is formulated as granules (PERLKA) that only slowly dissolve in a soil environment. Exposure of the aquatic environment will be exclusively due to runoff from agricultural fields. As above, cyanamide is the chemical moiety relevant for exposure due to rapid transformation from calcium cyanamide to cyanamide.
(Please note: direct release of the product to surface waters is strictly advised against, thus not a relevant exposure pathway.
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")

Reason / purpose for cross-reference:

read-across source

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

28.97 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

18.39 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

30.66 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

6.64 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: development rate

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

11.24 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: development rate

Details on results:

After 28 days, the emergence in the water control was 87 %. The emergence was not significantly inhibited up to 36.0 mg of the 51 % aqueous solution of cyanamide/L. At the highest test concentration the inhibition of emergence was 98 %. The calculated emergence ratio was not significantly reduced at treatment concentrations at or below 36.0 mg of the 51 % aqueous solution of cyanamide/L.
The development rate as an indicator of an emergence delay was not significantly reduced at treatment concentrations of 13.0 mg of the 51 % aqueous solution of cyanamide/L and below. Only one of the test vessels of the 22.0 mg/L test concentration level indicate a significant difference in number of male to number of female. Due to the fact that at higher test concentrations no respective effect was observed, no concentration effect relationship was found. Therefore, the calculation of the toxicological endpoints was performed with the pooled number of male and female midges.

Results with reference substance (positive control):

No positive control

Reported statistics and error estimates:

Not indicated

Analysis of cyanamide in overlying water

The results indicated that cyanamide decreased with time in the overlying water for the test vessels of 3.0 and 22.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L. After 7 days only about the half of the initial concentration was found. After 28 days the cyanamide concentration was found below the limit of quantification. For the highest concentration level the decrease started after the 7th day of exposure and even at 28th day of exposure cyanamide was found above the limit of quantification. The active substance cyanamide was degraded to 3.3 % of the initial nominal concentration at the highest test concentration and to less than 1 % of the initial nominal concentration at the lower concentration levels.

Analysis of cyanamide in pore water

With a latency of 7 days at the highest concentration level the results indicated that cyanamide decreased with time in the pore water.

Analysis of cyanamide in sediment

Less than 0.5 % of cyanamide was transferred to the sediment.

Analytical determination of concentrations tested in the water phase:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean measured test concentrations (mg/L) of samples taken after
	0 d	7 d	28 d
Water control	< LOQ	< LOQ	< LOQ
3.0	1.75	0.69	< LOQ
22.0	13.8	8.20	< LOQ
100.0	46.2	57.7	1.0

LOQ = 0.154 mg/L

Analytical determination of concentrations tested in the pore water:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean measured test concentrations (mg/L) of samples taken after
	0 d	7 d	28 d
Water control	< LOQ	< LOQ	< LOQ
3.0	0.59	< LOQ	< LOQ
22.0	1.75	0.65	< LOQ
100.0	1.74	5.07	< LOQ

LOQ = 0.154 mg/L

Analytical determination of concentrations tested in the sediment:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean measured test concentrations                                                               (mg/kg)                                of samples taken after
	0 d	7 d	28 d
Water control	< LOQ	< LOQ	< LOQ
3.0	< LOQ	< LOQ	< LOQ
22.0	< LOQ	< LOQ	< LOQ
100.0	1.0	< LOQ	< LOQ

LOQ = 0.154 mg/L

Summary of emergence data of Chironomus ripariusto a 51 % (w/w) aqueous solution of cyanamide for 28 days:

Nominal concentrations of the 51 % (w/w) aqueous solution of cyanamide (mg/L)	Mean emergence (%)	Mean development rate (%)	Males – number of emerging adults	Females – number of emerging adults
Water control	87.0	0.0629	40	47
3.0	84.0	0.0646	38	46
5.0	98.0	0.0608	38	61
8.0	78.0	0.0643	36	42
13.0	85.0	0.0624	48	40
22.0	96.0	0.0562	27	69
36.0	84.0	0.0550	36	48
60.0	37.0	0.0502	19	18
100.0	2.0	0.0457	1	1

No chironomids emerged before day 14

Validity criteria fulfilled:

yes

Conclusions:

*Emergence inhibition:
EC50 (28d) = 56.7 mg of a 51 % (w/w) aqueous solution of cyanamide/L (28.97 mg ai/L)

*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)
LOEC (28d) = 22.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (11.24 mg ai/L)

*Based on nominal initial overlying water concentrations).

Upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide.
Therefore, ecotoxicity in natural aquatic environments can be expressed in terms of cyanamide, irrespective of the substance constituting the exposure source. This is supported by experimental results: After stoichiometric correction of test concentrations, toxic effect values of cyanamide and calcium cyanamide are very similar in all standard test organisms. Thus, read-across from cyanamide to calcium cyanamide is justified for aquatic environmental endpoints.
For agricultural applications, calcium cyanamide is formulated as granules (PERLKA) that only slowly dissolve in a soil environment. Exposure of the aquatic environment will be exclusively due to runoff from agricultural fields. As above, cyanamide is the chemical moiety relevant for exposure due to rapid transformation from calcium cyanamide to cyanamide.
(Please note: direct release of the product to surface waters is strictly advised against, thus not a relevant exposure pathway.
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".)

Executive summary:

The effect of a 51 % (w/w) aqueous solution of cyanamide on Chironomus riparius was determined in an aerated, 28-day emergence test which was conducted in a similar way to the OECD 219. 25 larvae of the first larval stage (2 - 3 days old) were added to each vessel 24 hours prior to treatment. Treatments consisted of a water control, 3.0, 5.0, 8.0, 13.0, 22.0, 36.0, 60.0 and 100.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L, corresponding to 1.53, 2.56, 4.1, 6.64, 11.24, 18.4, 30.66 and 51.1 mg as/L. Four replicates were used for each treatment. Analysis of cyanamide was performed in overlying water, in pore water and in sediment. After 28 days, the emergence in the water control was 87 %. The emergence was not significantly inhibited up to 36.0 mg of the 51 % aqueous solution of cyanamide/L. At the highest test concentration the inhibition of emergence was 98 %. The calculated emergence ratio was not significantly reduced at treatment concentrations at or below 36.0 mg of the 51 % aqueous solution of cyanamide/L. The development rate as an indicator of an emergence delay was not significantly reduced at treatment concentrations of 13.0 mg of the 51 % aqueous solution of cyanamide/L and below. Only one of the test vessels of the 22.0 mg/L test concentration level indicate a significant difference in number of male to number of female. Due to the fact that at higher test concentrations no respective effect was observed, no concentration effect relationship was found. Therefore, the calculation of the toxicological endpoints was performed with the pooled number of male and female midges.

Based on nominal initial overlying water concentrations, 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) and 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), LOEC (28d) = 22.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (11.24 mg ai/L).

This information is used in a read-across approach in the assessment of the target substance.

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"

Description of key information

In the absence of data for calcium cyanamide, the assessment is based on data available for the read-across substance cyanamide:

The long-term toxicity of cyanamide to aquatic insects was examined in one available study. 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);

- 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

Upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide.

Therefore, ecotoxicity in natural aquatic environments can be expressed in terms of cyanamide, irrespective of the substance constituting the exposure source. This is supported by experimental results: After stoichiometric correction of test concentrations, toxic effect values of cyanamide and calcium cyanamide are very similar in all standard test organisms. Thus, read-across from cyanamide to calcium cyanamide is justified for aquatic environmental endpoints.

For agricultural applications, calcium cyanamide is formulated as granules (PERLKA) that only slowly degrades in a soil environment. Exposure of the aquatic environment will be exclusively due to runoff from agricultural fields. As above, cyanamide is the chemical moiety relevant for exposure due to rapid transformation from calcium cyanamide to cyanamide.

(Please note: direct release of the product to surface waters is strictly advised against, thus not a relevant exposure pathway.

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")

The long-term toxicity of cyanamide to aquatic insects was examined in one available study. 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 which was conducted in a similar was to the OECD 219. 25 larvae of the first larval stage (2 - 3 days old) were added to each vessel 24 hours prior to treatment. Treatments consisted of a water control, 3.0, 5.0, 8.0, 13.0, 22.0, 36.0, 60.0 and 100.0 mg of the 51 % (w/w) aqueous solution of cyanamide/L, corresponding to 1.53, 2.56, 4.1, 6.64, 11.24, 18.4, 30.66 and 51.1 mg as/L. Four replicates were used for each treatment. Analysis of cyanamide was performed in overlying water, in pore water and in sediment.

After 28 days, the emergence in the water control was 87 %. The emergence was not significantly inhibited up to 36.0 mg of the 51 % aqueous solution of cyanamide/L. At the highest test concentration the inhibition of emergence was 98 %. The calculated emergence ratio was not significantly reduced at treatment concentrations at or below 36.0 mg of the 51 % aqueous solution of cyanamide/L. The development rate as an indicator of an emergence delay was not significantly reduced at treatment concentrations of 13.0 mg of the 51 % aqueous solution of cyanamide/L and below. Only one of the test vessels of the 22.0 mg/L test concentration level indicate a significant difference in number of male to number of female. Due to the fact that at higher test concentrations no respective effect was observed, no concentration effect relationship was found. Therefore, the calculation of the toxicological endpoints was performed with the pooled number of male and female midges.

Based on nominal initial overlying water concentrations, 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);

- Emergence ratio NOEC (28d) = 36.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (18.39 mg ai/L) and 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), LOEC (28d) = 22.0 mg of a 51 % (w/w) aqueous solution of cyanamide/L (11.24 mg ai/L).