Isooctadecanoic acid, mixed esters with oxybis[propanediol]

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Remarks:

Ready and Ultimate Biodegradability

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

8 Aug - 5 Sep 1996

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

large variability between test vessels

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Version 1994

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Remarks:

activated sludge plant secondary effluent

Details on inoculum:

- Source of inoculum/activated sludge: secondary effluent from an unacclimatised activated sludge plant at the test facility
- Pretreatment: Filtration through Whatman filter paper (541) to remove coarse particulate matter; pH was adjusted to 6.5, followed by sparging with nitrogen in order to lower the level of dissolved inorganic carbon.
- Concentration of sludge: 10% (v/v)

Duration of test (contact time):

28 d

Initial conc.:

10.4 mg/L

Based on:

other: based on organic carbon, not specified

Initial conc.:

13.01 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salts medium
- Test temperature: 20-22°C
- pH: 6.5
- pH adjusted: yes

TEST SYSTEM
- Culturing apparatus: vessels of 160 mL volume (Hypovials)
- Measuring equipment: Analysis of the headspace gas and the liquid medium for CO2/Dissolved Inorganic Carbon was performed according to Ecotoxicology SOP 147 03, Ionics 555 Inorganic Carbon Analyser.

SAMPLING
- Sampling frequency: on day 4, 7, 11, 14, 19, 21, 25 and 28
- Sampling method: One vessel per substance and control was analysed on each day except on day 28 when six vessels were analysed.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

53.7

Sampling time:

28 d

Remarks on result:

other: Variability between replicates > 20%. 95% CI: 24.9-82.5%

Details on results:

In the 6 analysed vessels on day 28, the following biodegradation of the test item was observed: 3.0, 43.2, 63.7, 66.1, 66.6 and 79.6%. The great variability from vessel to vessel also showed in the previous analyses between day 4 and 25 where sample from different bottles were analysed. It is suspected that the test systems were not all dosed with the full amount of test substance. From these results it was not possible to come to any firm conclusion as to the biodegradability of the test substance. Despite the large variability, the results indicate that the substance is under going degradation to an appreciable amount and is possibly ultimately biodegradable.

Results with reference substance:

Sodium benzoate achieved 99.2% biodegradation after 28 days and the 60% pass level was reached within 10 days of exceeding the 10% level. Consequently sodium benzoate can be regarded as readily biodegradable thereby confirming the suitability of the inoculum and the culture conditions.

Table 1: Percentage biodegradation over 28 day test period

Day No.	% Biodegradation of the test substance
4	35.1
7	45.1
11	52.9
14	9.3
18	71.2
21	19.2
25	76.4
28	66.1, 79.6, 66.6, 63.7, 3.0, 43.2
mean 28	53.7
95% CI	24.9 – 82.5

Table 2: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	> 20%	no
Percentage degradation of the reference compound has reached the pass levels by day 14.	96.6%	yes

Validity criteria fulfilled:

no

Remarks:

variability between replicates > 20%

Interpretation of results:

other: While an appreciable amount of biodegradation occured and there is evidence of ultimate biodegradation, a firm conclusion as to the biodegradability of the test substance was not possible due to the large variability of the results.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 May - 11 June 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

17 July, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

December 1992

Deviations:

no

GLP compliance:

yes

Remarks:

Carbon analysis was not performed under GLP conditions.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: freshly obtained from a municipal sewage treatment plant, Waterschap de Maaskant, s'Hertogenbusch, Netherlands
- Storage conditions: sludge was kept under continous aeration until further treatment
- Preparation of inoculum for exposure: Before use, the sludge was allowed to settle for at least 30 minutes and the liquid decanted.
- Concentration of sludge: 3.6 g/L of suspended solids
- Initial cell/biomass concentration: concentration of sludge supernatant: 1.44 x 10E5 cells/mL; the test system contained 1.44 x 10E3 cells/mL

Duration of test (contact time):

28 d

Initial conc.:

16.5 mg/L

Based on:

test mat.

Initial conc.:

12 mg/L

Based on:

other: total carbon content

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium:
A) 8.50 g KH2PO4, 21.75 g K2HPO4, 67.20 g Na2HPO4 x 12 H2O, 0.50 g NH4Cl, dissolved in 1L MilliQ water, pH 7.4 +/- 0.2
B) 22.50 g MgSO4 x 7 H2O dissolved in 1L MilliQ water
C) 36.40 g CaCl2 x 2 H2O dissolved in 1L MilliQ water
D) 0.25 FeCl3 x 6 H2O dissolved in 1L MilliQ water
1 litre mineral medium contained 10 mL of solution A) and 1 mL of solutions B) to D) and MilliQ water
- Test temperature: 20-22°C
- pH (range between test start and end): 7.5- 8.0
- Preparation of test solutions: mineral components, MilliQ water (ca. 80 % total volume) and inoculum (1% final volume) were added to each bottle. This mixture was aerated with CO2-free air overnight to purge the system of CO2.

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration: 2 each for test substance and inoculum blank; 1 each for reference substance and toxicity control
- Method used to create aerobic conditions: The test was started by bubbling CO2-free air through the solution (rate ca. 30-100 mL/min).
- Details of trap for CO2 and volatile organics if used: 4 g Ba(OH)2 x 8 H2O per L MilliQ water was filtered through filter paper and stored in a sealed vessel to prevent absorption of CO2 from air. Three CO2 absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2 were connected in series to the exit air line of each test bottle.

SAMPLING
- Sampling frequency: every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day
- Sampling method: Titration with Phenolphthalein as indicator; the CO2 produced in each test bottle reacted with the Ba(OH)2 in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardised HCl.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes, containing test substance, reference substance and inoculum
- Positive control: yes, with sodium acetate as reference substance

Reference substance:

acetic acid, sodium salt

Remarks:

ca. 40 mg/L, corresponding to TOC=12 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

65

Sampling time:

28 d

Remarks on result:

other: Test material; Replicate A

Parameter:

% degradation (CO2 evolution)

Value:

80

Sampling time:

28 d

Remarks on result:

other: Test material; Replicate B

Parameter:

% degradation (CO2 evolution)

Value:

59

Sampling time:

14 d

Remarks on result:

other: Toxicity control; based on ThCO2

Results with reference substance:

60% degradation of the reference substance was recorded on day 9

Table 1: % Degradation of the test substance

Day No.	% Biodegradation of the test substance
	Replicate A	Replicate B
2	0.1	1.0
5	1.2	2.9
7	15.5	16.2
9	26.9	28.1
14	33.2	45.7
19	58.3	65.6
23	59.3	73.7
27	61.9	76.9
29	64.5	79.9

Table 2: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	< 20%	yes
Percentage degradation of the reference compound has reached the pass levels by day 14 (>60%).	64.6%	yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	59.0%	yes

The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.

28.1 mg/L

yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to "Any other information on results incl. tables."

Interpretation of results:

readily biodegradable, but failing 10-day window

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 May - 11 June 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

17 July, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

December 1992

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: freshly obtained from a municipal sewage treatment plant, Waterschap de Maaskant, s'Hertogenbusch, Netherlands
- Storage conditions: sludge was kept under continous aeration until further treatment
- Preparation of inoculum for exposure: Before use, the sludge was allowed to settle for at least 30 minutes and the liquid decanted.
- Concentration of sludge: 3.6 g/L of suspended solids
- Initial cell/biomass concentration: concentration of sludge supernatant: 1.44 x 10E5 cells/mL; the test system contained 1.44 x 10E3 cells/mL

Duration of test (contact time):

28 d

Initial conc.:

17 mg/L

Based on:

test mat.

Initial conc.:

12 mg/L

Based on:

other: total carbon

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium:
A) 8.50 g KH2PO4, 21.75 g K2HPO4, 67.20 g Na2HPO4 x 12 H2O, 0.50 g NH4Cl, dissolved in 1L MilliQ water, pH 7.4 +/- 0.2
B) 22.50 g MgSO4 x 7 H2O dissolved in 1L MilliQ water
C) 36.40 g CaCl2 x 2 H2O dissolved in 1L MilliQ water
D) 0.25 FeCl3 x 6 H2O dissolved in 1L MilliQ water
1 litre mineral medium contained 10 mL of solution A) and 1 mL of solutions B) to D) and MilliQ water
- Test temperature: 20-22°C
- pH (range between test start and end): 7.5- 8.0
- Preparation of test solutions: mineral components, MilliQ water (ca. 80 % total volume) and inoculum (1% final volume) were added to each bottle. This mixture was aerated with CO2-free air overnight to purge the system of CO2.

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration: 2 each for test substance and inoculum blank; 1 each for reference substance and toxicity control
- Method used to create aerobic conditions: The test was started by bubbling CO2-free air through the solution (rate ca. 30-100 mL/min).
- Details of trap for CO2 and volatile organics if used: 4 g Ba(OH)2 x 8 H2O per L MilliQ water was filtered through filter paper and stored in a sealed vessel to prevent absorption of CO2 from air. Three CO2 absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2 were connected in series to the exit air line of each test bottle.

SAMPLING
- Sampling frequency: every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day
- Sampling method: Titration with Phenolphthalein as indicator; the CO2 produced in each test bottle reacted with the Ba(OH)2 in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardised HCl.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes, containing test substance, reference substance and inoculum
- Positive control: yes, with sodium acetate as reference substance

Reference substance:

acetic acid, sodium salt

Remarks:

40 mg/L, corresponding to TOC=12 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

77

Sampling time:

28 d

Remarks on result:

other: test material; Replicate A

Parameter:

% degradation (CO2 evolution)

Value:

95

Sampling time:

28 d

Remarks on result:

other: test material; Replicate B

Parameter:

% degradation (CO2 evolution)

Value:

43.7

Sampling time:

14 d

Remarks on result:

other: Toxicity control; based on ThCO2

Details on results:

The test material reached the pass level of 60% within 10 days after exceeding 10%.

Results with reference substance:

The reference control containing sodium acetate reached the pass level of 60% biodegradation by day 14.

Table 1: % Degradation of the test substance

Day No.	% Biodegradation of the test substance
	Replicate A	Replicate B
2	0.1	0.8
5	0.1	0.8
7	0.1	7.2
9	4.0	13.2
14	29.9	44.7
19	60.2	72.1
23	70.5	80.2
27	77.4	86.5
29	77.4	95.4

Table 2: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	< 20%	yes
Percentage degradation of the reference compound has reached the pass levels by day 14 (>60%).	64.6%	yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	43.7%	yes

The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.

28.1 mg/L

yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to "Any other information on results incl. tables."

Interpretation of results:

readily biodegradable

Description of key information

The target substance is considered not readily biodegradable.

Additional information

The target substance Isooctadecanoic acid, mixed esters with oxybis[propanediol] exists as two different grades. Grade One is characterized by mainly triesters of C18 iso fatty acids of the alcohol component diglycerol. Grade Two is characterized by mainly tetraesters of C18 iso fatty acids of the alcohol component diglycerol. There is one study available investigating the ready biodegradability ofGrade Two of the target substanceIsooctadecanoic acid, mixed esters with oxybis[propanediol]. However, this study was disregarded due to large variability between replicates.

The source substance Isooctadecanoic acid, ester with oxybis[propanediol] (CAS 73296-86-3) also exists as two different grades. It is characterized as a UVCB substance with mainly monoesters (Grade One) and mainly diesters, respectively (Grade Two), of C18 iso fatty acids of the alcohol component polyglycerol. One study per grade is available for the source substance Isooctadecanoic acid, ester with oxybis[propanediol] (CAS 73296-86-3).

In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5, a read-across to the two grades of the structurally related source substance Isooctadecanoic acid, mixed esters with oxybis[propanediol] was conducted. This read-across is justified in detail within the analogue justification in IUCLID Section 13.

Both studies were conducted in identical test designs under GLP conditions and according to OECD Guideline 301 B (CO2 evolution test) and EU method C-4.C. The studies were performed under aerobic conditions using microorganisms from a municipal sewage treatment plant. The initial concentration of the test material in the test medium was 17 mg/L, corresponding to 12 mg/L total carbon content.

In the first study with Isooctadecanoic acid, ester with oxybis[propanediol] (CAS 73296-86-3; Grade One), biodegradation rates of 77-95 % after 28 days were observed. The 10-day-window was met. The substance can therefore be considered readily biodegradable according to OECD criteria.

In the second study with Isooctadecanoic acid, ester with oxybis[propanediol] (CAS 73296-86-3; Grade Two), the degradation rate was 65-80% after 28 days. The substance failed to meet the 10-day-window. The substance is therefore not readily biodegradable according to OECD criteria.

The tested batch in the study with Isooctadecanoic acid, ester with oxybis[propanediol] (CAS 73296-86-3; Grade One) had higher a content of monoesters while the batch in the second study with Isooctadecanoic acid, ester with oxybis[propanediol] (CAS 73296-86-3; Grade Two) consisted of a larger amount of diesters. Conclusively, the rate of biodegradation decreases with an increasing degree of esterification of the alcohol component diglycerol. Since the target substance with both grades is characterized by mainly tri- and tetraesters of C18 iso fatty acids, it can be concluded that Isooctadecanoic acid, mixed esters with oxybis[propanediol] is not readily biodegradable based on data from the source substance CAS 73296-86-3. This is supported by the disregarded study withIsooctadecanoic acid, mixed esters with oxybis[propanediol] (Grade Two) where a mean degradation rate of 53.7% (95% CI: 24.9 – 82.5%) was observed after 28 days.

Based on the available results from the structurally related read-across substances (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by a similar ecotoxicological profile and comparable structure and the disregarded substance for the target substance, it is concluded that Isooctadecanoic acid, mixed esters with oxybis[propanediol] can be expected to be not readily biodegradable according to the OECD guideline criteria.