2-cyano-2-[2,3-dihydro-3-(tetrahydro-2,4,6-trioxo-5(2H)-pyrimidinylidene)-1H-isoindol-1-ylidene]-N-methylacetamide

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
see attached justification

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP compliant guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum: Chemicals Evaluation and Research Institute, Japan
- Culturing: Once a day, the supernatant solution was removed about one-third the total amount and synthetic waste water was refilled

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Parameter followed for biodegradation estimation:

DOC removal

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Test volume: 300 ml
- Solubilising agent (type and concentration if used):
- Test temperature: 25 °C
- pH: 7.2 - 7.8

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

0 - 10

Sampling time:

28 d

Details on results:

Degradability based on DOC removal after 28 d: 0 - 10 %
Degradability based on residual test substance concentration after 28 d: 0 - 10 %

Suspended matter of the insoluble test substance was observed in test bottles.

Results with reference substance:

- Degradability of aniline (based on BOD): 53 % at day 7

Interpretation of results:

under test conditions no biodegradation observed

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Principles of method if other than guideline:

Estimation of results of OECD screening tests on ready biodegradation in water: CATALOGIC (v5.14.1.5); CATALOGIC 301C v.11.16

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Duration of test (contact time):

28 d

Parameter:

half-life in days (QSAR/QSPR)

Remarks on result:

other: Primary half life: 2.71 days; Ultimate half life: 1y 0m 5d

Parameter:

probability of ready biodegradability (QSAR/QSPR)

Remarks on result:

not readily biodegradable based on QSAR/QSPR prediction

Details on results:

Model domain similarity:
- Parametric domain: 100%
- Structural domain: 100%
- Mechanistic domain: 100%

Predicted BOD value: 0.18 +/- 7.10E-3

Prediction: not ready degradable

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance is not readily biodegradable (according to OECD criteria)

Cross-reference 3

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

additional information on environmental fate and behaviour

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 318

GLP compliance:

no

At any of the time points mentioned in the TG-318, the influence of Ca is critical. Regardless of pH, the pigment is unstable in 10 mM Ca, representing high water hardness. After 6h, the samples showed high dispersion stability in 0 mM Ca, intermediate stability in 1 mM and 10 mM Ca at pH values 4 and 9 and low stability 1 mM and 10 mM Ca at pH 7. After 24 hours the stability in 0 mM Ca remained high. For the samples in 1 and 10 mM Ca the stability was low.

 

Table 1: full results of the dispersion stability in the presence of NOM

	Ca(NO3)2	Stability after 6h	Standard deviation	Stability after 15h	Standard deviation	Stability after 24h	Standard deviation
	[mM]	[%]	[%]	[%]	[%]	[%]	[%]
pH 4	0	103.9	1.0	105.3	0.9	99.7	7.1
pH 4	1	13.4	0.8	5.3	0.3	4.1	0.3
pH 4	10	14.8	2.7	4.8	0.9	3.3	0.6
.
pH 7	0	97.3	0.4	95.5	0.3	94.5	0.4
pH 7	1	7.0	4.2	2.9	1.5	1.8	0.6
pH 7	10	9.2	3.9	4.0	1.4	2.4	4.2
.
pH 9	0	99.6	0.6	99.5	0.7	98.5	0.8
pH 9	1	15.6	0.9	6.9	0.3	5.1	0.6
pH 9	10	13.9	4.5	7.5	1.9	5.7	1.8

 

To rationalize the observed dispersion stability, we finally checked the particle size distribution directly in the environmental medium. We applied the NanoDefine method of Analytical Ultracentrifugation. The centrifugation parameters are given in the methods section.

As required by TG318, paragraph 31, the tested nanomaterial was pre-wetted in ultrapure water and left in the form of wet-paste for 24 h. The TG318 requires this step “to insure the proper interaction of nanomaterial surface with ultrapure water.” We visually observed incomplete wetting, and so any ensuing measurement would have been incorrect. In accord with the NanoGenoTox dispersion protocol, a drop of ethanol was added, successfully transferred the powder into a paste, which was then further diluted as specified in the TG318

The observed size distributions confirm the moderate agglomeration at 1 mM Ca, pH7, with NOM. If the particles would have been significantly dissolved, no size distribution would be observable at all by this method, which relies on the detection of the movement of particles during centrifugal separation.

Additionally, the centrifugation methods include a determination of the remaining absorption after centrifugation, fully consistent with the conventional determination of the dissolved fraction after centrifugation as recommended by the TG-318. The remaining absorption was measured at ca. 0.21. This is a fraction of 10% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 10% of the sample may have been dissolved.

All evidence combined, the results after centrifugation confirm that at least 90% of the observed dispersion stability has to be attributed to the particles, not to dissolution.

 

Executive summary:

At any of the time points mentioned in the TG-318, the influence of Ca is critical. Regardless of pH, the pigment is unstable in 10 mM Ca, representing high water hardness. After 6h, the samples showed high dispersion stability in 0 mM Ca, intermediate stability in 1 mM and 10 mM Ca at pH values 4 and 9 and low stability 1 mM and 10 mM Ca at pH 7. After 24 hours the stability in 0 mM Ca remained high. For the samples in 1 and 10 mM Ca the stability was low.

Results and discussion

Transformation products:

no

Remarks:

Since the substance is highly insoluble in water, simulation biodegradation tests in water and sediment are not proposed, since no relevant new findings are expected from such investigations.