Calcium cyanamide

Phototransformation in water

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991-06-26 to 1991-12-13

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Study type:

direct photolysis

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water)

Version / remarks:

, October 1982

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Analytical method:

other: TLC

Details on sampling:

Non-exposed and exposed samples were analysed at 0, 1, 3, 7, 14, 21 and 30 days for total radioactivity by LSC.

Buffers:

The photolytic stability of [14C]-Cyanamide was studied in aqueous solutions buffered at pH values of 5 and 7.

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

> 290 - < 400

Details on light source:

Test samples were installed in a photolysis chamber using a xenon arc lamp (290 - 400 nm). In addition dark controls, wrapped in foil, were incubated in the photolysis chamber.

Details on test conditions:

14C-Cyanamide was dissolved in methanol (262 µg/mL) and a [12C]/[14C]-isotopic dilution was prepared by adding 924 mg of non-radiolabelled Cyanamide to the stock solution in order to ensure an adequate amount of test material resulting in a concentration of 18.7 mg as/mL (radiochemical purity: 96.8 %). Aqueous solutions with [14C]-Cyanamide were prepared at nominal concentrations of 20 µg/mL and were continuously irradiated under sterile conditions for up to 30 days at 25 ± 1 °C in a photolysis chamber using a xenon arc lamp. In addition dark controls, wrapped in foil, were incubated in the photolysis chamber.

Duration:

30 d

Temp.:

25 °C

Initial conc. measured:

20 other: µg/mL

Reference substance:

no

Dark controls:

yes

Computational methods:

The rate of degradation of Cyanamide was determined using linear regression assuming first order reaction kinetics (DT50).

Key result

% Degr.:

48.2

Sampling time:

30 d

Test condition:

Light exposed samples at pH 5

Key result

% Degr.:

58.2

Sampling time:

30 d

Test condition:

Light exposed samples at pH 7

Key result

% Degr.:

80.5

Sampling time:

30 d

Test condition:

Dark control samples at pH 5

Key result

% Degr.:

86.6

Sampling time:

30 d

Test condition:

Dark control samples at pH 7

Key result

DT50:

28.9 d

Test condition:

Light exposed samples at pH 5

Key result

DT50:

116 d

Test condition:

Non-exposed samples at pH 5

Key result

DT50:

38.5 d

Test condition:

Light exposed samples at pH 7

Key result

DT50:

139 d

Test condition:

Non-exposed samples at pH 7

Predicted environmental photolytic half-life:

Under laboratory conditions (Xenon lamp 290 - 400 nm), Cyanamide was moderately degraded. Quantum yield was not determined in the presented study, since the adsorption coefficient at 290 nm is below 10 in UV-VIS spectra. Therefore, it can be concluded that in contrary to the laboratory conditions natural irradiation in Central Europe does not cause relevant direct photolytic degradation.

Transformation products:

yes

No.:

#1

Details on results:

Degradation of the test substance Cyanamide was observed in the exposed systems of both buffer solutions. The Cyanamide concentration in the light exposed samples decreased after 30 days to 48.2 % of initial measured dose (IMD) and 58.2 % of IMD at pH 5 and pH 7, respectively. In the dark control samples the Cyanamide concentration decreased to 80.5 % and 86.6 % of IMD at pH 5 and pH 7 after 30 days.

One major degradation product, identified as urea, was detected in the light exposed samples at maximum concentrations of 12.2 % of initial measured dose (IMD) at pH 7 and 42.4 % of IMD at pH 5. Urea was also detected in the pH 5 dark control samples at concentrations up to 8.18 % of IMD.
Photolytic half-lives were calculated using first-order degradation kinetics and were determined to be 28.9 d and 38.5 d in the light exposed samples at pH 5 and pH 7, respectively. DT50 values of the dark control samples were calculated to be 116 d and 139 d at pH 5 and pH 7, respectively.

- The mass balance in light exposed and dark control samples ranged from 89.1 to 103 % of applied radioactivity with mean recoveries of 98.3 % for light exposed samples and 96.1 % for dark control samples

- Quantum yield was not determined in the presented study, since the adsorption coefficient at 290 nm is below 10 in UV-VIS spectra

- Under laboratory conditions (Xenon lamp 290 - 400 nm), Cyanamide was moderately degraded

Photochemical degradation of¹⁴C-Cyanamide in sterile buffers:

Time	System	pH 5			pH 7
		Total^14C	Cyanamide	Urea	Total^14C	Cyanamide	Urea
0	-	100	94.0	n.d.	100	96.7	n.d.
1	NON EXP	99.5 100	95.1 96.3	n.d. n.d.	103 102	99.8 95.6	n.d. n.d.
3	NON EXP	100 100	93.1 91.9	1.96 3.28	100 101	96.5 91.1	n.d. 1.78
7	NON EXP	100 99.0	89.7 87.6	4.32 6.59	102 101	96.9 87.1	n.d. 3.49
14	NON EXP	91.7 95.1	81.6 70.3	4.77 19.3	94.6 90.1	88.7 70.9	n.d. 6.57
21	NON EXP	92.6 93.1	82.5 56.7	5.60 30.5	94.6 89.1	87.3 61.6	n.d. 9.0
30	NON EXP	92.6 93.6	80.5 48.2	8.18 42.4	94.1 89.6	86.6 58.2	n.d. 12.2

Photochemical degradation of [¹⁴C]-Cyanamide in sterile buffers:

pH	System	DT50[d]	R^2
5	NON	116	0.9282
	EXP	28.9	0.9924
7	NON	139	0.9293
	EXP	38.5	0.9827

Validity criteria fulfilled:

yes

Conclusions:

The results show that photodegradation of Cyanamide occurred in aqueous solution buffered at pH 5 and 7. Photolytic half-lives were calculated to be 28.9 d and 38.5 d in the light-exposed samples at pH 5 and pH 7, respectively. Urea was detected as major degradation product in the light-exposed samples at maximum concentrations of 12.2 % of IMD at pH 7 and 42.4 % of IMD at pH 5. Urea was also detected in the pH 5 dark control samples at concentrations up to 8.18 % of IMD. These data indicate that photolysis is a more significant degradation pathway at pH 5 and pH 7 (25 °C) than hydrolysis
2. Under laboratory conditions (Xenon lamp 290 - 400 nm), Cyanamide was moderately degraded. Quantum yield was not determined in the presented study, since the adsorption coefficient at 290 nm is below 10 in UV-VIS spectra. Therefore, it can be concluded that in contrary to the laboratory conditions natural irradiation in Central Europe does not cause relevant direct photolytic degradation.

Executive summary:

The photolytic stability of [14C]-Cyanamide was studied in aqueous solutions buffered at pH values of 5 and 7. For this purpose 14C-Cyanamide was dissolved in methanol (262 µg/mL) and a [12C]/[14C]-isotopic dilution was prepared by adding 924 mg of non-radiolabelled Cyanamide to the stock solution in order to ensure an adequate amount of test material resulting in a concentration of 18.7 mg as/mL (radiochemical purity: 96.8 %). Aqueous solutions with [14C]-Cyanamide were prepared at nominal concentrations of 20 µg/mL and were continuously irradiated under sterile conditions for up to 30 days at 25 ± 1 °C in a photolysis chamber using a xenon arc lamp. In addition dark controls, wrapped in foil, were incubated in the photolysis chamber. Non-exposed and exposed samples were analysed at 0, 1, 3, 7, 14, 21 and 30 days for total radioactivity by LSC. For identification of parent compound and degradation products the samples were analysed by reversed-phase TLC. Selected samples were analysed by HPLC with UV detection to confirm the amounts and identities of the residues identified by TLC. The rate of degradation of Cyanamide was determined using linear regression assuming first order reaction kinetics. The results show that photodegradation of Cyanamide occurred in aqueous solution buffered at pH 5 and 7. The Cyanamide concentration in the light exposed samples decreased after 30 days to 48.2 % of initial measured dose (IMD) and 58.2 % of IMD at pH 5 and pH 7, respectively. In the dark control samples the Cyanamide concentration decreased to 80.5 % and 86.6 % of IMD at pH 5 and pH 7 after 30 days. Photolytic half-lives were calculated to be 28.9 d and 38.5 d in the light exposed samples at pH 5 and pH 7, respectively. Urea was detected as major degradation product in the light-exposed samples at maximum concentrations of 12.2 % of IMD at pH 7 and 42.4 % of IMD at pH 5. Urea was also detected in the pH 5 dark control samples at concentrations up to 8.18 % of IMD. These data indicate that photolysis is a more significant degradation pathway at pH 5 and pH 7 (25 °C) than hydrolysis.

Reference 2

Endpoint:

phototransformation in water

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, available information on cyanamide is used in the assessment of calcium cyanamide in a read-across approach.
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

Key result

% Degr.:

48.2

Sampling time:

30 d

Test condition:

Light exposed samples at pH 5

Key result

% Degr.:

58.2

Sampling time:

30 d

Test condition:

Light exposed samples at pH 7

Key result

% Degr.:

80.5

Sampling time:

30 d

Test condition:

Dark control samples at pH 5

Key result

% Degr.:

86.6

Sampling time:

30 d

Test condition:

Dark control samples at pH 7

Key result

DT50:

28.9 d

Test condition:

Light exposed samples at pH 5

Key result

DT50:

116 d

Test condition:

Non-exposed samples at pH 5

Key result

DT50:

38.5 d

Test condition:

Light exposed samples at pH 7

Key result

DT50:

139 d

Test condition:

Non-exposed samples at pH 7

Predicted environmental photolytic half-life:

Under laboratory conditions (Xenon lamp 290 - 400 nm), Cyanamide was moderately degraded. Quantum yield was not determined in the presented study, since the adsorption coefficient at 290 nm is below 10 in UV-VIS spectra. Therefore, it can be concluded that in contrary to the laboratory conditions natural irradiation in Central Europe does not cause relevant direct photolytic degradation.

Transformation products:

yes

No.:

#1

Details on results:

Degradation of the test substance Cyanamide was observed in the exposed systems of both buffer solutions. The Cyanamide concentration in the light exposed samples decreased after 30 days to 48.2 % of initial measured dose (IMD) and 58.2 % of IMD at pH 5 and pH 7, respectively. In the dark control samples the Cyanamide concentration decreased to 80.5 % and 86.6 % of IMD at pH 5 and pH 7 after 30 days.

One major degradation product, identified as urea, was detected in the light exposed samples at maximum concentrations of 12.2 % of initial measured dose (IMD) at pH 7 and 42.4 % of IMD at pH 5. Urea was also detected in the pH 5 dark control samples at concentrations up to 8.18 % of IMD.
Photolytic half-lives were calculated using first-order degradation kinetics and were determined to be 28.9 d and 38.5 d in the light exposed samples at pH 5 and pH 7, respectively. DT50 values of the dark control samples were calculated to be 116 d and 139 d at pH 5 and pH 7, respectively.

- The mass balance in light exposed and dark control samples ranged from 89.1 to 103 % of applied radioactivity with mean recoveries of 98.3 % for light exposed samples and 96.1 % for dark control samples

- Quantum yield was not determined in the presented study, since the adsorption coefficient at 290 nm is below 10 in UV-VIS spectra

- Under laboratory conditions (Xenon lamp 290 - 400 nm), Cyanamide was moderately degraded

Photochemical degradation of¹⁴C-Cyanamide in sterile buffers:

Time	System	pH 5			pH 7
		Total^14C	Cyanamide	Urea	Total^14C	Cyanamide	Urea
0	-	100	94.0	n.d.	100	96.7	n.d.
1	NON EXP	99.5 100	95.1 96.3	n.d. n.d.	103 102	99.8 95.6	n.d. n.d.
3	NON EXP	100 100	93.1 91.9	1.96 3.28	100 101	96.5 91.1	n.d. 1.78
7	NON EXP	100 99.0	89.7 87.6	4.32 6.59	102 101	96.9 87.1	n.d. 3.49
14	NON EXP	91.7 95.1	81.6 70.3	4.77 19.3	94.6 90.1	88.7 70.9	n.d. 6.57
21	NON EXP	92.6 93.1	82.5 56.7	5.60 30.5	94.6 89.1	87.3 61.6	n.d. 9.0
30	NON EXP	92.6 93.6	80.5 48.2	8.18 42.4	94.1 89.6	86.6 58.2	n.d. 12.2

Photochemical degradation of [¹⁴C]-Cyanamide in sterile buffers:

pH	System	DT50[d]	R^2
5	NON	116	0.9282
	EXP	28.9	0.9924
7	NON	139	0.9293
	EXP	38.5	0.9827

Validity criteria fulfilled:

yes

Conclusions:

The results show that photodegradation of Cyanamide occurred in aqueous solution buffered at pH 5 and 7. Photolytic half-lives were calculated to be 28.9 d and 38.5 d in the light-exposed samples at pH 5 and pH 7, respectively. Urea was detected as major degradation product in the light-exposed samples at maximum concentrations of 12.2 % of IMD at pH 7 and 42.4 % of IMD at pH 5. Urea was also detected in the pH 5 dark control samples at concentrations up to 8.18 % of IMD. These data indicate that photolysis is a more significant degradation pathway at pH 5 and pH 7 (25 °C) than hydrolysis
2. Under laboratory conditions (Xenon lamp 290 - 400 nm), Cyanamide was moderately degraded. Quantum yield was not determined in the presented study, since the adsorption coefficient at 290 nm is below 10 in UV-VIS spectra. Therefore, it can be concluded that in contrary to the laboratory conditions natural irradiation in Central Europe does not cause relevant direct photolytic degradation.

Upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide. Therefore, available information on cyanamide is used in the assessment of calcium cyanamide in a read-across approach.
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 photolytic stability of [14C]-Cyanamide was studied in aqueous solutions buffered at pH values of 5 and 7. For this purpose 14C-Cyanamide was dissolved in methanol (262 µg/mL) and a [12C]/[14C]-isotopic dilution was prepared by adding 924 mg of non-radiolabelled Cyanamide to the stock solution in order to ensure an adequate amount of test material resulting in a concentration of 18.7 mg as/mL (radiochemical purity: 96.8 %). Aqueous solutions with [14C]-Cyanamide were prepared at nominal concentrations of 20 µg/mL and were continuously irradiated under sterile conditions for up to 30 days at 25 ± 1 °C in a photolysis chamber using a xenon arc lamp. In addition dark controls, wrapped in foil, were incubated in the photolysis chamber. Non-exposed and exposed samples were analysed at 0, 1, 3, 7, 14, 21 and 30 days for total radioactivity by LSC. For identification of parent compound and degradation products the samples were analysed by reversed-phase TLC. Selected samples were analysed by HPLC with UV detection to confirm the amounts and identities of the residues identified by TLC. The rate of degradation of Cyanamide was determined using linear regression assuming first order reaction kinetics. The results show that photodegradation of Cyanamide occurred in aqueous solution buffered at pH 5 and 7. The Cyanamide concentration in the light exposed samples decreased after 30 days to 48.2 % of initial measured dose (IMD) and 58.2 % of IMD at pH 5 and pH 7, respectively. In the dark control samples the Cyanamide concentration decreased to 80.5 % and 86.6 % of IMD at pH 5 and pH 7 after 30 days. Photolytic half-lives were calculated to be 28.9 d and 38.5 d in the light exposed samples at pH 5 and pH 7, respectively. Urea was detected as major degradation product in the light-exposed samples at maximum concentrations of 12.2 % of IMD at pH 7 and 42.4 % of IMD at pH 5. Urea was also detected in the pH 5 dark control samples at concentrations up to 8.18 % of IMD. These data indicate that photolysis is a more significant degradation pathway at pH 5 and pH 7 (25 °C) than hydrolysis.

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

Upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide. Therefore, available data for the phototransformation of hydrogen cyanamide in water are used in a read-across approach for the assessment of calcium cyanamide.

The photolytical half-life of cyanamide in buffered aqueous solutions was calculated to be 28.9 days and 38.5 days at pH 5 and pH 7, respectively. Urea was detected as major degradation product in the light exposed samples.

The half-life of 38.5 days at pH 7 is carried forward as key value for chemical safety assessment.

Key value for chemical safety assessment

Half-life in water:

38.5 d

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"