Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

Toxicity control from biodegradation study.

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 Aug - 07 Sep 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The solution of the reference substance in mineral medium (100 mg/L) was prepared using a stock solution (10 g/L). Required amounts of the test item were added directly to the test vessels and the mineral medium was added subsequently.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Source of inoculum/activated sludge: Sewage treatment plant Ruhrverband Kläranlage, Sunthelle 6, 57392 Schmallenberg, Germany
- Date of sampling: 10th August 2016
- Storage conditions: No storage
- Preparation of inoculum for exposure: No washing, the concentration was adjusted to 3.0 g/L and verified by dry mass measurement.
- Pretreatment: Kept aerobic until use
- Concentration of sludge in the test: 29.6 mg dry mass/litre

Test type:

static

Water media type:

freshwater

Total exposure duration:

28 d

Test temperature:

22 ± 1 °C

pH:

7.4 ± 0.2 (test start)
7.8 (test end)

Nominal and measured concentrations:

20, and 100 mg/L test item (nominal) corresponding to 61, and 305 mg ThOD/L

Details on test conditions:

TEST SYSTEM
- Toxicity control: Containing 100 mg/L test item and 100 mg/L reference item (2 replicates)
- Test vessel: Respirometer flasks (SAPROMAT respirometer (VOITH Inc.)
- Material, size, headspace, fill volume: 500 mL respirometer flasks filled with 250 mL test solution.
- Aeration: The suspension was aerated during the whole test.
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per abiotic control (replicates): 2
- Sludge concentration: 29.6 mg dry mass/litre
- Other: The solutions were stirred throughout the test.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Deionized water, free from inhibitory concentrations of toxic substances (e.g. Cu2+ ions)

OTHER TEST CONDITIONS
- Adjustment of pH: Before test start the pH of all solutions were determined and adjusted to 7.4 ± 0.2 with H2SO4 (50 g/L).
- Photoperiod: 24 h darkness

EFFECT PARAMETERS MEASURED:
Oxygen consumption was measured and recorded continuously throughout the duration of the test using a SAPROMAT respirometer (VOITH Inc.).

Reference substance (positive control):

yes

Remarks:

sodium benzoate

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other:

Remarks:

Toxicity control from a biodegradation study.

Details on results:

In absence of a microbial inhibition test, a NOEC for microbial toxicity can be derived from a ready biodegradability test. According to Chapter R.7b: Endpoint specific guidance (ECHA, 2017) 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.

The test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration.

Percent degradation. Degradation (%) after 14 days.

vessel		Test suspension 100 mg/L	Test suspension 20 mg/L	Abiotic control	Procedural control	Toxicity control
1		45.2	88.4	0.0	86.5	42.8
2		45.9	78.6	0.0	84.7	47.5
Mean		45.5	83.5	0.0	85.6	45.1
SD		0.5	6.9	0.0	1.3	3.3

Percent degradation. Degradation (%) after 28 days.

vessel		Test suspension 100 mg/L	Test suspension 20 mg/L	Abiotic control	Procedural control	Toxicity control
1		67.5	88.4	0.0	91.3	57.4
2		65.5	83.5	0.0	91.3	64.2
Mean		66.5	86.0	0.0	91.3	60.8
SD		1.4	3.5	0.0	0.0	4.8

Validity criteria fulfilled:

yes

Conclusions:

The test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L (nominal).

Description of key information

NOEC (14 d) ≥ 100.0 mg/L for activated sludge microorganisms (OECD 301 F)

Additional information

There is no respiration inhibition study available assessing the toxicity of Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) to activated sludge microorganisms. However, a standard ready biodegradability test conducted according to OECD guideline 301 F and GLP is available, whose toxicity control can be used to derive a NOEC. According to the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA, 2017), a concentration can be used as NOEC value, if a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration.

The available ready biodegradability test included a toxicity control containing 100 mg/L test item and 100 mg/L reference item (benzoic acid, sodium salt) to determine the possible toxicity to microorganisms of activated sludge at a concentration of 29.6 mg dry mass/L.

After 14 d, a mean biodegradation of 45.1% was observed and after 28 d a mean biodegradation of 60.8% was recorded in the toxicity control. In the procedural controls, the reference substance sodium benzoate was degraded by an average of 86% by exposure day 14, and reached an average biodegradation of 91% by the end of the test (day 28), thus confirming the suitability of the activated sludge. Hence, Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration and a NOEC (14 d) of ≥ 100.0 mg/L (nominal) was derived.