Cyanamide

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-06-26 until 1995-07-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Deviations:

yes

Remarks:

, see below

Principles of method if other than guideline:

According to OECD 202 (adopted 1984), the deviation from the initial pH should be < 0.3 units. Furthermore, the dissolved oxygen concentration in all test solutions should be checked once every 48 hours. Temperature, dissolved oxygen and pH were measured on days 0, 4, 7, 14 and 21 in alternating duplicate replicates (test chambers A and B on days 0, 7 and 21 and test chambers C and D on days 4 and 14) of the control and all test levels. However, the pH-values ranged from 7.78 to 8.45 and differed more than 0.3 units. The dissolved oxygen was not measured once every 48 h, but the measured percent saturation were > 79 %, thus full-filling the guideline requirements. These deviations are considered to have no impact on the validity of the study.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Mean measured concentrations of cyanamide were 0.023, 0.049, 0.1, 0.21 and 0.41 mg /L and ranged from 92 to 105 % of nominal concentrations. In the test medium the test item was sufficiently stable during the test period of 21 days.

Vehicle:

no

Details on test solutions:

Not indicated

Test organisms (species):

Daphnia magna

Details on test organisms:

The Daphnia magna were < 24-hours old

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

No post exposure observation period

Hardness:

Not indicated

Test temperature:

20.5°C - 21.2°C

pH:

The pH-values ranged from 7.78 to 8.45

Dissolved oxygen:

> 79 %

Salinity:

Freshwater

Nominal and measured concentrations:

Nominal concentrations of 0.025, 0.05, 0.1, 0.2 and 0.4 mg of cyanamide/L.
Mean measured concentrations of cyanamide were 0.023, 0.049, 0.1, 0.21 and 0.41 mg /L and ranged from 92 to 105 % of nominal concentrations.

Details on test conditions:

Forty daphnids (4 replicates containing 10 daphnids each) were exposed to each test level. Removals of neonates were performed on Monday, Wednesday and Friday after first brood release in the control. The daphnids were fed 4.0 x 108 cells/mL per litre of test solution of an algal suspension (Selenastrum capricornutum / Ankistrodesmus falcatus) and 0.5 mL per test chamber of a 5.0 mg/mL suspension of trout chow and yeast.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 0.41 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

> 0.104 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Details on results:

Survival of Daphnia magna was not significantly affected in any test level when compared to the control. The day 21 EC50 based on immobility was > 0.41 mg cyanamide/L (based on mean measured test concentrations).
The 0.023 and 0.41 mg/L test levels were significantly different when compared to the control for adult length. The length was not significantly different in the other concentrations compared to the control. The data for the 0.023 mg/L test level were considered aberrant because they did not follow a normal dose-response pattern. Also, the 0.023 mg/L test level had the second highest number of young/adult/reproduction day of all the test levels and control. The significant difference at the 0.41 mg/L test level is considered a test material effect.

The mean weights were not significantly different from the control at any test concentration. The time to first brood was 7 days for the control and all test concentrations. Thus, it can be concluded that the time to first brood is not influenced by cyanamide.

The 0.41 mg/L test level was significantly different when compared to the control for the reproduction mean. The remaining levels were not significantly different from the control. There were no sublethal (behavioural) effects noted at any test concentration. Based on the effects on length and reproduction mean at the 0.41 mg/L test level, the LOEC can be identified as 0.21 mg/L (based on mean measured test concentrations). Based on the lack of weight, length, survival and reproduction effects, the 0.1 mg/L test level can be identified as NOEC (>0.1 mg/L based on mean measured test concentrations).

Results with reference substance (positive control):

No positive control

Reported statistics and error estimates:

The test groups were significantly different from control according to the Dunnett test, P < 0.05

Summary of test endpoints following exposure of Daphnia magnato to cyanamide for 21 days:

Mean measured concentrations of cyanamide (mg /L)	Mean adult survival^a (%)	Mean first day of reproduction^b	Mean total alive young^c	Mean adult length (mm)	Mean adult dry weight (mg)
Water Control	100.0	7.0	10.83	4.74	0.97
0.023	100.0	7.0	10.91	4.53*	0.88
0.049	97.5	7.0	11.50	4.63	0.91
0.10	95.0	7.0	10.49	4.68	0.97
0.21	100.0	7.0	9.64	4.61	0.98
0.41	97.5	7.0	8.54*	4.53*	0.92

^a Percent of adult daphnids alive at the end of the test (immobility was synonymous with death)

^b First day that reproduction was observed in the replicates

^c Mean of live young produced per surviving female per reproduction day

*Significantly different from control according to the Dunnett test, p < 0.05.

 

Chronic toxicity (21-d) of cyanamide to daphnids – Summary of endpoints:

Endpoints	Mean measured concentration of cyanamide
EC50(immobility)	> 0.41 mg/L
No observed effect concentration (NOEC)	>0.1 mg/L

 

 

Validity criteria fulfilled:

yes

Remarks:

see above in "principles of methods if other than guideline". The deviations are considered to have no impact on the validity of the study.

Conclusions:

The 21 day EC50 based on immobility was > 0.41 mg cyanamide/L. The 21 day NOEC (no-observed effect concentration), based on mean measured concentrations and the parameters ”young per adult”, ”reproduction day” and ”length” was >0.1 mg cyanamide/L, for Daphnia magna neonates exposed for 21 days under flow-through conditions.

Executive summary:

The effects of of cyanamide on the growth and reproduction of Daphnia magna (< 24-hours old) were assessed in an unaerated, flow-through, 21-day test. Treatments consisted of a water control and nominal concentrations of 0.025, 0.05, 0.1, 0.2 and 0.4 mg cyanamide/L. Forty daphnids (4 replicates contain 10 daphnids) were exposed to each test level.

 

All chemical and physical parameters (dissolved oxygen concentration, temperature) in the definitive test were within expected ranges. Mean measured concentrations of cyanamide were 0.023, 0.049, 0.1, 0.21 and 0.41 mg /L and ranged from 92 to 105 % of nominal concentrations. In the test medium the test item was sufficiently stable during the test period of 21 days.

Survival of Daphnia magna was not significantly affected in any test level when compared to the control. The day 21 EC50 based on immobility was > 0.41 mg cyanamide/L (based on mean measured test concentrations).

 

The 0.023 and 0.41 mg/L test levels were significantly different when compared to the control for adult length. The length was not significantly different in the other concentrations compared to the control. The data for the 0.023 mg/L test level were considered aberrant because they did not follow a normal dose-response pattern. Also, the 0.023 mg/L test level had the second highest number of young/adult/reproduction day of all the test levels and control. The significant difference at the 0.41 mg/L test level is considered a test material effect.

 

The mean weights were not significantly different from the control at any test concentration. The time to first brood was 7 days for the control and all test concentrations. Thus, it can be concluded that the time to first brood is not influenced by cyanamide.

 

The 0.41 mg/L test level was significantly different when compared to the control for the reproduction mean. The remaining levels were not significantly different from the control. There were no sublethal (behavioural) effects noted at any test concentration.

 

Based on the effects on length and reproduction mean at the 0.41 mg/L test level, the EC50 can be identified as 0.41 mg/L (based on mean measured test concentrations). Based on the lack of weight, length, survival and reproduction effects, the >0.1 mg/L test level can be identified as NOEC.

 

The available long-term studies do not change the classification.

Description of key information

The long-term toxicity of cyanamide to aquatic invertebrates was examined in one available study. In the study the growth and reproduction of Daphnia magna were assessed in an unaerated, flow-through, 21-day test. An EC50 of > 0.41 mg cyanamide/L and NOEC of 0.1044 mg cyanamide/L were calculated from the obtained results.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

0.104 mg/L

Additional information

The effects of of cyanamide on the growth and reproduction of Daphnia magna (< 24-hours old) were assessed in an unaerated, flow-through, 21-day test. Treatments consisted of a water control and nominal concentrations of 0.025, 0.05, 0.1, 0.2 and 0.4 mg cyanamide/L. Forty daphnids (4 replicates contain 10 daphnids) were exposed to each test level.

 

All chemical and physical parameters (dissolved oxygen concentration, temperature) in the definitive test were within expected ranges. Mean measured concentrations of cyanamide were 0.023, 0.049, 0.1, 0.21 and 0.41 mg /L and ranged from 92 to 105 % of nominal concentrations. In the test medium the test item was sufficiently stable during the test period of 21 days.

 

Survival of Daphnia magna was not significantly affected in any test level when compared to the control. The day 21 EC50 based on immobility was > 0.41 mg cyanamide/L (based on mean measured test concentrations).

 

The 0.023 and 0.41 mg/L test levels were significantly different when compared to the control for adult length. The length was not significantly different in the other concentrations compared to the control. The data for the 0.023 mg/L test level were considered aberrant because they did not follow a normal dose-response pattern. Also, the 0.023 mg/L test level had the second highest number of young/adult/reproduction day of all the test levels and control. The significant difference at the 0.41 mg/L test level is considered a test material effect.

 

The mean weights were not significantly different from the control at any test concentration. The time to first brood was 7 days for the control and all test concentrations. Thus, it can be concluded that the time to first brood is not influenced by cyanamide.

 

The 0.41 mg/L test level was significantly different when compared to the control for the reproduction mean. The remaining levels were not significantly different from the control. There were no sublethal (behavioural) effects noted at any test concentration.

 

Based on the effects on length and reproduction mean at the 0.41 mg/L test level, the EC50 can be identified as 0.41 mg/L (based on mean measured test concentrations). Based on the lack of weight, length, survival and reproduction effects, the >0.1 mg/L (0.1044 mg/L) test level can be identified as NOEC.