Cyanamide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

Deviations:

yes

Remarks:

The medium contained a buffer of higher capacity than the described one in the OECD Guideline. But this deviation has no effect on the validity of the study.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Not indicated

Duration of test (contact time):

28 d

Initial conc.:

14.7 mg/L

Based on:

act. ingr.

Initial conc.:

29.4 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

- The nutrient medium was inoculated with activated sludge. A stock solution of aqueous hydrogen cyanamide solution was prepared in nutrient medium
- A stock solution of aqueous hydrogen cyanamide solution was prepared in nutrient medium. Two concentrations of 49 % (w/w) aqueous solution of cyanamide (30 and 60 mg/L corresponding to 4 and 9 mg DOC/L and to 14.7 and 29.4 mg as/L) were tested by adding the respective amounts of stock solution to inoculated nutrient media
- Control flasks without test substance and a sterile control (test medium autoclaved for 20 minutes at 120 °C) were included in the test
- Sodium acetate was used as a positive control
- The test samples were incubated for 28 days at 20°± 2 °C and aliquots were collected from each flask after 0, 1, 2, 3 and 4 weeks
- The residual dissolved organic carbon (DOC) was measured using a TOC-Analyser after persulphate oxidation to assess the percent of biodegradation.

Reference substance:

acetic acid, sodium salt

Preliminary study:

No preliminary study

Test performance:

No special remarks on test performance

Key result

Parameter:

% degradation (DOC removal)

Value:

0

Sampling time:

28 d

Remarks on result:

other: Same biodegradadble result (%) was obtained also before the 28th day sampling time (after 0,7, 14, 21 days of exposure).

Details on results:

Cyanamide was not degraded in the inoculated medium within 28 days. Therefore, cyanamide is regarded as not readily biodegradable by the terms of this test. No degradation was found in the sterile control confirming the stability of the test substance.

Results with reference substance:

The biodegradability of sodium acetate was used as a measure for the microbial activity of the inoculum, and to detect any inhibition of this activity due to the presence of high concentrations of cyanamide. Sodium acetate was completely degraded within one week i.e. biodegradation reached a level of 97 to 100 % indicating that sodium acetate is readily biodegradable by the terms of this test. The sodium acetate degradation was not influenced by cyanamide present in the medium.

No remarks

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Cyanamide is regarded as not readily biodegradable by the terms of this test.

Executive summary:

The nutrient medium was prepared as described in OECD 301 E with one exception: solution (a) contained 1.5 g NH4Cl/1000 mL instead of 0.5 g/1000 mL. The nutrient medium was inoculated with activated sludge. A stock solution of aqueous hydrogen cyanamide solution was prepared in nutrient medium. Two concentrations of 49 % (w/w) aqueous solution of cyanamide (30 and 60 mg/L corresponding to 4 and 9 mg DOC/L and to 14.7 and 29.4 mg as/L) were tested by adding the respective amounts of stock solution to inoculated nutrient media. Control flasks without test substance and a sterile control (test medium autoclaved for 20 minutes at 120 °C) were included in the test. Sodium acetate was used as a positive control. The test samples were incubated for 28 days at 20 ± 2 °C and aliquots were collected from each flask after 0, 1, 2, 3 and 4 weeks. The residual dissolved organic carbon (DOC) was measured using a TOC-Analyser after persulphate oxidation to assess the percent of biodegradation. The biodegradability of sodium acetate was used as a measure for the microbial activity of the inoculum, and to detect any inhibition of this activity due to the presence of high concentrations of cyanamide. Sodium acetate was completely degraded within one week i.e. biodegradation reached a level of 97 to 100 % indicating that sodium acetate is readily biodegradable by the terms of this test. The sodium acetate degradation was not influenced by cyanamide present in the medium. Cyanamide was not degraded in the inoculated medium within 28 days. Therefore, cyanamide is regarded as not readily biodegradable by the terms of this test. No degradation was found in the sterile control confirming the stability of the test substance. As literature data indicated that cyanamide should be readily biodegradable (in contrast to the results of this study), the influence of some limiting factors (i.e. nitrogen source, test substance and inoculum concentrations) on the biodegradability of cyanamide was determined in another study (Matla, 1990 Doc. No.713-002).

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

Modified Sturm Test (1981)

Deviations:

yes

Remarks:

The medium contained a buffer of higher capacity than the described one in the OECD Guideline. But this deviation has no effect on the validity of the study.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Activated sludge was added to the medium to reach inoculum concentrations of approximately 30 mg (dry weight) and approximately 100 mg (dry weight) per litre.

Duration of test (contact time):

56 d

Initial conc.:

1 mg/L

Based on:

act. ingr.

Initial conc.:

15 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

- Nutrient medium was prepared as described in OECD 301 B with one exception: solution (a) contained 1.5 g NH4Cl/1000 mL instead of 0.5 g/1000 mL. One nitrogen free medium was prepared leaving out NH4Cl and yeast extract for the testing of Cyanamide as nitrogen source
- The media were aerated for 24 hours with CO2-free air before use
- Activated sludge was added to the medium to reach inoculum concentrations of approximately 30 mg (dry weight) and approximately 100 mg (dry weight) per liter
- The test samples were incubated for 56 days at 20 ± 2°C and aliquots were collected from each flask after 0, 13, 28 and 56 days
- Evolving CO2 was trapped in NaOH traps and its amount determined by titration with 0.1 M HCL
- The following tests were performed:
Nitrogen limitation: A 49 % (w/w) aqueous solution of cyanamide was added to the inoculated medium at a concentration of 1 mg/L in order to serve as the sole source of carbon and nitrogen. In additional flasks the inoculated medium was incubated with cyanamide (as possible nitrogen source) and sodium acetate (100 mg/L), as carbon source.

Test substance and inoculum concentration: To nutrient medium with an inoculum concentration of 30 mg (d.w.)/L and 100 mg (d.w.)/L, respectively, a 49 % (w/w) aqueous solution of cyanamide was added at concentrations of 1.0 and 15 mg as/L, respectively.

Reference substance:

other: was not used

Preliminary study:

No preliminary study

Test performance:

No special remarks on test performance

Key result

Parameter:

% degradation (CO2 evolution)

Value:

100

Sampling time:

13 d

Remarks on result:

other: Cyanamide was completely degraded within two weeks when it served as nitrogen source for degradation of a carbon-containing compound (sodium acetate).

Key result

Parameter:

% degradation (CO2 evolution)

Value:

22

Sampling time:

56 d

Remarks on result:

other: Cyanamide served as both carbon and nitrogen source. The obtained result was therefore slower (22% within 8 weeks) than the result obtained when cyanamide served only as a nitrogen source.

Details on results:

Nitrogen limitation:
Cyanamide was completely degraded within two weeks when it served as a nitrogen source for degradation of a carbon-containing compound (sodium acetate). When cyanamide served as both carbon and nitrogen source it was degraded slowly with about 22 % within 8 weeks.
Test substance and inoculum concentration:
Neither the test substance concentration nor the inoculum concentration influenced the ready biodegradability of cyanamide.

Validity criteria fulfilled:

yes

Interpretation of results:

other: The biodegradation of cyanamide in a standard ready biodegradability test is prevented by the presence of another easily available nitrogen source.

Conclusions:

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.

Executive summary:

The study was performed in order to determine the influence of some limiting factors (i.e. nitrogen source, test substance and inoculum concentrations) on the biodegradability of cyanamide. For this purpose a nutrient medium was prepared as described in OECD 301 B with one exception: solution (a) contained 1.5 g NH4Cl/1000 mL instead of 0.5 g/1000 mL. One nitrogen free medium was prepared leaving out NH4Cl and yeast extract for the testing of cyanamide as nitrogen source. The media were aerated for 24 hours with CO2-free air before use. Activated sludge was added to the medium to reach inoculum concentrations of approximately 30 mg (dry weight) and approximately 100 mg (dry weight) per liter. The test samples were incubated for 56 days at 20 ± 2 °C and aliquots were collected from each flask after 0, 13, 28 and 56 days. Evolving CO2 was trapped in NaOH traps and its amount determined by titration with 0.1 M HCL.

 

The following tests were performed

Nitrogen limitation

A 49 % (w/w) aqueous solution of cyanamide was added to the inoculated medium at a concentration of 1 mg/L in order to serve as the sole source of carbon and nitrogen. In additional flasks the inoculated medium was incubated with cyanamide (as possible nitrogen source) and sodium acetate (100 mg/L), as carbon source.

Test substance and inoculum concentration: To nutrient medium with an inoculum concentration of 30 mg (d.w.)/L and 100 mg (d.w.)/L, respectively, a 49 % (w/w) aqueous solution of cyanamide was added at concentrations of 1.0 and 15 mg as/L, respectively.

 

Nitrogen limitation

Cyanamide was completely degraded within two weeks when it served as a nitrogen source for degradation of a carbon-containing compound (sodium acetate). When cyanamide served as both carbon and nitrogen source it was degraded slowly with about 22 % within 8 weeks.

Test substance and inoculum concentration: Neither the test substance concentration nor the inoculum concentration influenced the ready biodegradability of cyanamide.

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.

Description of key information

The result of the study of van der Hoeck showed that cyanamide can be regarded as not readily 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. But, as rapid degradation of cyanamide could clearly be demonstrated under environmentally realistic conditions in 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".

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

Two ready biodegradable studies were conducted in which the newer study (Malta, 1990) examined the influence of some limiting factors on the biodegradability of cyanamide that might explain the not readily biodegradadble result obtained by the former study (van der Hoeck, 1988).

 

In the study of van der Hoeck (1988) a stock solution of aqueous Hydrogen cyanamide solution was prepared in nutrient medium inoculated with activated sludge in two concentrations corresponding to 14.7 and 29.4 mg ai cyanamide/L. Control flasks without test substance and a sterile control (test medium autoclaved for 20 minutes at 120 °C) were included in the test. Sodium acetate was used as a positive control. The test samples were incubated for 28 days at 20°± 2 °C. The residual dissolved organic carbon (DOC) was measured using a TOC-Analyser after persulphate oxidation to assess the percent of biodegradation. The biodegradability of sodium acetate was used as a measure for the microbial activity of the inoculum, and to detect any inhibition of this activity due to the presence of high concentrations of cyanamide.

 

Sodium acetate was completely degraded within one week i.e. biodegradation reached a level of 97 to 100 % indicating that sodium acetate is readily biodegradable by the terms of this test. The sodium acetate degradation was not influenced by cyanamide present in the medium. Cyanamide was not degraded in the inoculated medium within 28 days. Therefore, cyanamide is regarded as not readily biodegradable by the terms of this test. No degradation was found in the sterile control confirming the stability of the test substance. As literature data indicate that cyanamide should be readily biodegradable (in contrast to the results of this study), the influence of some limiting factors (i.e. nitrogen source, test substance and inoculum concentrations) on the biodegradability of cyanamide was determined in another study (Malta, 1990).

 

For this purpose in the study of Malta (1990), one nitrogen free medium was prepared leaving out NH4Cl and yeast extract for the testing of cyanamide as nitrogen source. Activated sludge was added to the medium and the test samples were incubated for 56 days at 20 ± 2°C. Evolving CO2 was trapped in NaOH traps and its amount determined by titration with 0.1 M HCL.

 

Results showed that in the nitrogen limitation samples the cyanamide was completely degraded within two weeks when it served as a nitrogen source for degradation of a carbon-containing compound (sodium acetate). When cyanamide served as both carbon and nitrogen source it was degraded slowly with about 22 % within 8 weeks. Results of the samples that examined the influence of the test substance and the inoculum concentrations showed that neither the test substance concentration nor the inoculum concentration influenced the biodegradability of cyanamide.

 

But, as rapid degradation of cyanamide could clearly be demonstrated under environmentally realistic conditions in 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".