Branched and linear octadecanoic acid, esters with glycerol oligomers

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data based on the inhibition control of a ready biodegradability study. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2016).

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD 310: Ready Biodegradability - CO2 in sealed vessels (Headspace Test)

Version / remarks:

26 Sep 2014

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ISO 14593, Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium - Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test)

Version / remarks:

15 Mar 1999

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OPPTS 835.3140, Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test), US EPA

Version / remarks:

Oct 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Hess. Ministerium für Umwelt, Energie, Landwirtschaft und Verbraucherschutz, Wiesbaden, Germany

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A stock solution of the test item in acetone was prepared (250.6 mg test item in 50 mL acetone). Appropriate amounts of this stock solution were dosed into the test vessels of the test item (0.5 mL, Ft) and the toxicity control (0.25 mL, Fl) and allowed to evaporate completely overnight before proceeding with the dosing of test water and activated sludge. For the preparation of the test item (Ft), activated sludge (2.5 mL of a stock solution 4 g/L suspended solids) was added to appropriate amounts of the test water (2500 mL) to achieve a sludge concentration of 4 mg/L. The mixture was stirred intensively and appropriate amounts were weighed into each test vessel, containing the evaporated test item and sealed with gas-tight septum caps.
- Inoculum controls (Fb): As the control vessels have to be treated in the same way as the test item vessels, 0.5 mL acetone was added and allowed to evaporate completely overnight before proceeding with the dosing of test water and activated sludge. Activated sludge (2.5 mL of the stock solution of 4 g suspended solids/L) was added to the test water (2500 mL) to achieve a sludge concentration of 4 mg/L. The mixture was stirred intensively and appropriate amounts were dispensed into the test vessels and sealed with gas-tight septum caps.
- Toxicity control (Fl): The toxicity control contains both, the test item and the reference item. The reference item was weighed into a total volume of test water (1500 mL) and activated sludge (1.5 mL of a stock solution of 4 g/L suspended solids) was added. The mixture was stirred intensively and appropriate amounts were weighed into the test vessels, containing the evaporated test item and sealed with gas-tight septum caps.
- Chemical name of vehicle: acetone
- Concentration of vehicle in test medium: As the procedure control (Fc) vessels have to be treated in the same way as the test item vessles, 0.5 mL acetone was added and allowed to evaporate completely overnight before proceeding with the dosing of test water and activated sludge. Appropriate amounts of the reference item sodium benzoate were weighed into a total volume of test water (1500 mL) and activated sludge (1.5 mL of the stock solution of 4 g suspended solids/L) was added to achieve a sludge concentration of 4 mg/L. The mixture was stirred intensively and approprate amounts were dispensed into the test vessels and sealed with gas-tight septum caps.

LOADING RATES
- Test item: 19.8 mg C/L (= 29.5 mg/L test item)
- Reference item: 19.8 mg C/L (= 34.0 mg/L reference item)
- Toxicity control: 19.8 mg C/L (= 14.7 mg/L test item and 17.0 mg/L of reference item)

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Source of inoculum/activated sludge: aeration tank of a municipal sewage treatment plant, Rossdorf, Germany
- Storage conditions: The washed sludge suspension was adjusted to 4 g dry material per litre and aerated overnight.
- Storage length: overnight
- Preparation of inoculum for exposure: The activated sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension were mixed with test water corresponding to 4 g dry material per litre and aerated overnight.
- Concentration of sludge: 4 mg/L (final concentration)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

14 d

Details on test conditions:

TEST CONDITIONS
- Composition of medium: Reconstituted water composed of analytical grade salts in pure water.
- Solubilising agent: acetone
- Test temperature: 20 ± 2 °C
- pH: 7.6
- pH adjusted: no
- Aeration of dilution water: Yes, the test water was aerated with CO2-free air prior to test start.
- Suspended solids concentration: 4 mg/L dw
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Glass bottles with screw-caps and Teflon-coated septa.
- Number of culture flasks/concentration: 3 replicates per treatment and per sampling
- Method used to create aerobic conditions: Aeration of the activated sludge and the test water with CO2-free air prior to test start.
- Measuring equipment: TOC-Analzyer, TOC-V CPH, Shimadzu
- Test performed in closed vessels due to significant volatility of test substance: The test vessel was sealed with gas-tight septum caps.
- Details of trap for CO2 and volatile organics if used:
- Other: The headspace to liquid ratio was 1:2.

SAMPLING
- Sampling frequency: Test item and Inoculum Control (blank): Days 0, 3, 6, 10, 14, 17, 20, 28; Procedure Control and Toxicity Control: Days 0, 6, 14, 28
- Sampling method: The produced CO2 was converted into carbonate using 7 M NaOH solution (0.8 mL to 85 mL test medium) injected into the test vessels at each sampling. The alkalised medium was shaken for 1 h and subjected to total inorganic carbon (TIC) analysis. TIC consists of the carbon contained in carbonates and in carbon dioxide dissolved in water. By acidification all carbonates are converted to carbon dioxide. Carbon dioxide and dissolved carbon dioxide in the sample are volatilized by bubbling CO2-free air through the sample. The TIC-content was analyzed automatically by the TOC-Analyzer using the sealed test vessels as sampling vials.
- Sample storage before analysis: The analysis was done immediately after sampling or the alkalised samples were stored in the refrigerator (4 ± 4°C) for a maximum of 4 d. Samples of Day 0 were stored deep frozen at < -20 °C for 4 d before analysis.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes, consisting of 0.5 mL acetone (evaporated overnight), activated sludge (4 mg/L) in test water (2500 mL).
- Toxicity control: Yes, consisting of the test item and the reference item in test water (1500 mL).
- Procedure Control: Yes, consisting of 0.5 mL acetone (evaporated overnight), reference item, activated sludge (4 mg/L) and test water (1500 mL).

Reference substance (positive control):

yes

Remarks:

sodium benzoate

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 14.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Results of toxicity control from ready biodegradability test

Results with reference substance (positive control):

The reference item (sodium benzoate) was sufficiently degraded to 84.3% after 14 d and to 66.0% after 28 d of incubation (Table 1). The percentage of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

In the toxicity control containing both the test item and the reference item sodium benzoate, 77.8% biodegradation was noted within 14 d and 65.6% biodegradation after 28 d of incubation. Therefore, the test item is not inhibitory to the inoculum.

Validity criteria fulfilled:

yes

Description of key information

NOEC (14 d) ≥ 14.7 mg/L (nominal, OECD 310)

Additional information

Since no studies on the toxicity of the target substance Polyaldo 2-1-IS (CAS 73296-86-3) to aquatic microorganisms are available, a ready biodegradability study is used to derive a NOEC for the toxicity to aquatic microorganisms. If a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2016).

A substance can be assumed to be not inhibitory to aquatic microorganisms, if in the toxicity control of a ready biodegradation test, more than 25% degradation based on CO2 evolution (CO2/ThCO2)] occurred within 14 d (OECD guideline 301). For the present substance a biodegradation test according to OECD guideline 310 is available. The test includes a toxicity control, which contains 14.7 mg/L of test substance and 17.0 mg/L of the reference material (sodium benzoate).

The toxicity control attained 77.8% degradation after 14 d of incubation. Hence, the substance is not toxic to aquatic microorganisms in the toxicity control and the test item concentration of 14.7 mg/L can be used as NOEC (NOEC (14 d) ≥ 14.7 mg/L).