Calcium 4-[(5-chloro-4-methyl-2-sulphonatophenyl)azo]-3-hydroxy-2-naphthoate

Biodegradation in soil

Administrative data

Endpoint:

biodegradation in soil: simulation testing

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Specific details on test material used for the study:

- Storage condition of test material: At room temperature at about 20 °C, away from direct sunlight

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: aerobic activated sludge from a wastewater treatment treating predominantly domestic wastewater
- Preparation of inoculum for exposure: Sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated. Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (±10%) dry material per liter. During the holding period of one day prior to use, the sludge was aerated at room temperature. Prior to use, the sludge was diluted with test water to a concentration of about 1 g dry material per liter. Defined volumes of this diluted activated sludge were added to test water to obtain a final concentration of 30 mg dry material per liter.

Duration of test (contact time):

28 d

Initial conc.:

33 mg/L

Based on:

test mat.

Initial conc.:

15.3 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: One day before test start (Day-1), between 2400 and 3000 mL of untreated test medium was filled into the flasks and 90 ml activated sludge inoculum was added. Then aeration overnight with C02-free air on the following day (Day 0), defined amounts of the test item were directly added to the test flasks and made up to a volume of 3 L with test water.
- Solubilising agent: none
- Test temperature: 21-23 °C
- pH: 7.2 - 7.4
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5-liter all-glass amber bottles
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: air was led through a bottle containing about 750 mL of a 2 M NaOH solution to trap CO2. The CO2-free air was passed through the test solutions at a rate corresponding to about 30-100 mL/min.
- Details of trap for CO2 and volatile organics: two absorber flasks, the first one containing 300 mL 0.05 M NaOH and the second one containing 200 mL 0.05 M NaOH, were connected in series to the exit air line of each test flask.

SAMPLING
- Sampling frequency test item and inoculum control: day 2, 5, 7, 9, 12, 14, 19, 23, 27, 28, 29
- Sampling frequency procedure control: day 2, 7, 14, 28, 29
- Sampling frequency toxicity control: day 7, 14, 28, 29
- Sampling method: aliquot of 5.0 mL withdrawn from the absorber flask nearest to the test flask for analysis of inorganic carbon

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Toxicity control: 1 replicate
- Procedure control: 2 replicates

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

28 d

Results with reference substance:

Mean degradation rate after 28 days = 77.1%

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

and ETAD method

Principles of method if other than guideline:

To measure the partition coefficient of pigments utilising the standard OECD Guideline 107 is extremely difficult because of the problems associated with the inherent very low solubilities. The following procedure is used for determining the LogPow of low solubility substances and in particular that of pigments.
The partition coefficient was estimated based on the ratio of the solubilities in n-octanol and in water. The individual solubilities were determined by flask method based on OECD Guideline 105 and the ETAD method.

A defined amount of the pigment (see table 1) was transferred to a 100 ml flask with glass stopper and 60 ml of water (deionised, 18.2 MOcm). This was stirred at 70°C for 2 hours, and then 72 hours in an air conditioned laboratory (T = 23°C). The suspension was then centrifuged (10 000 rpm, 10 min) and filtered once through a standard paper filter, twice through a 0.2 μm membrane filter (Millipore) and twice through a 0.025μm membrane filter (Millipore). If particles were detected in the solution (turbidity), the final filtration step was repeated until a perfectly clear solution was acheived.
The above procedure was conducted in parallel for a total of 2 water (deionised, 18.2 MOcm) samples and of 2 n-octanol (Sigma-Aldrich, spectrophotometric grade) samples.

GLP compliance:

no

Type of method:

flask method

Key result

Water solubility:

>= 250 - <= 280 µg/L

Conc. based on:

test mat. (total fraction)

Incubation duration:

72 h

Temp.:

23 °C

pH:

>= 4.5 - <= 5

Remarks on result:

other: pH of the test water

Conclusions:

The water solubility of test substance was determined to be 250 - 280 µg/L at 23°C.

Cross-reference 3

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 105 and ETAD method

Principles of method if other than guideline:

To measure the partition coefficient of pigments utilising the standard OECD Guideline 107 is extremely difficult because of the problems associated with the inherent very low solubilities. The following procedure is used for determining the LogPow of low solubility substances and in particular that of pigments.
The partition coefficient was estimated based on the ratio of the solubilities in n-octanol and in water. The individual solubilities were determined by flask method based on OECD Guideline 105 and the ETAD method.

A defined amount of the pigment (see table 1) was transferred to a 100 ml flask with glass stopper and 60 ml of water (deionised, 18.2 MOcm). This was stirred at 70°C for 2 hours, and then 72 hours in an air conditioned laboratory (T = 23°C). The suspension was then centrifuged (10 000 rpm, 10 min) and filtered once through a standard paper filter, twice through a 0.2 μm membrane filter (Millipore) and twice through a 0.025μm membrane filter (Millipore). If particles were detected in the solution (turbidity), the final filtration step was repeated until a perfectly clear solution was acheived.
The above procedure was conducted in parallel for a total of 2 water (deionised, 18.2 MOcm) samples and of 2 n-octanol (Sigma-Aldrich, spectrophotometric grade) samples.

GLP compliance:

no

Type of method:

estimation method (solubility ratio)

Partition coefficient type:

octanol-water

Analytical method:

photometric method

Key result

Type:

log Pow

Partition coefficient:

-0.75

Temp.:

23 °C

Remarks on result:

other: pH value not reported

Details on results:

Solubiliy in n-octanol: 43-52 µg/L
Solubility in water: 250-280 µg/L
Weight in n-octanol/water: 57.2-59.3 mg/100 mL

Conclusions:

The partition coefficient of test substance was estimated to be log Pow= -0.75 at 23°C.

Cross-reference 4

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

additional information on environmental fate and behaviour

Remarks:

Dispersion stability in simulated environmental media

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 318

GLP compliance:

yes (incl. QA statement)

At any of the time points mentioned in the TG-318, the influence of Ca is critical. Regardless of pH, the pigment is categorized at the 24h-sampling time as “unstable” in 10 mM Ca, representing high water hardness.

After 6h, the stability for the samples in 0 mM Ca and at pH 4 in 1 mM Ca was high. Stability at all other conditions was at lower end of the intermediate level.

After 24 hours the stability for samples in 0 mM Ca and at pH 4 in 1 mM Ca remained high. Stability at all other conditions 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	100	0.6	100	0.7	100	1.0
pH 4	1	100	0.1	100	0.1	100	0.1
pH 4	10	12.5	0.3	7.3	0.3	5.9	0.2
.
pH 7	0	100	0.3	100	0.3	100	0.3
pH 7	1	15.1	1.6	8.3	0.7	6.5	0.3
pH 7	10	14.7	1.1	10.0	1.2	8.7	0.9
.
pH 9	0	100	0.5	100	0.6	100	0.7
pH 9	1	17.8	1.4	9.1	0.1	7.6	0.1
pH 9	10	17.3	2.1	10.8	0.1	9.3	1.4

 

To rationalize the observed dispersion stability, we finally checked the particle size distribution directly in the environmental medium (exact same sample preparation as for the UV/VIS measurements). We applied the NanoDefine method of Analytical Ultracentrifugation (SOP AUC-RI, published by³). The centrifugation parameters are given in the methods section.

 

The observed size distributions confirm the moderate agglomeration at 1 mM Ca, pH7, with NOM (Figure 4). 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 c.a 0.04. This is a fraction of 3% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 3% of the sample may have been dissolved.

 

All evidence combined, the results after centrifugation confirm that at least 97% of the observed dispersion stability has to be attributed to the particles, not to dissolution.

Executive summary:

Elevated apparent dispersion stability may originate from dissolution. The dissolution in environmental media has not yet been assessed, but the particle size distribution was measured in all media. The remaining absorption after centrifugal separation of particles was determined to be not more than 3% of the total signal. Thus, dissolution is not the main cause of the observed stability.

 

Taken together, the dispersion stability of Pigment Red 48:2 depends especially on pH and water hardness. The stability for samples in 0 mM Ca and at pH 4 in 1 mM Ca was high. Stability at all other conditions was low.