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Toxicity to microorganisms

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Endpoint:
toxicity to microorganisms, other
Remarks:
Data based on the toxicity control of a standard ready biodegradability study (OECD 301 F). This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2016).
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reason / purpose for cross-reference:
read-across source
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:
Source: CAS 97338-28-8, Stéarinerie, 2016, Manometric Respirometry Test
Conclusions:
No toxicity to microorganisms was recorded up to the limit of water solubility (OECD 301 F, activated sludge microorganisms).
Endpoint:
toxicity to microorganisms, other
Remarks:
Manometric Respirometry Test
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)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): 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
Limit test:
yes
Total exposure duration:
28 d
Nominal and measured concentrations:
20.0 and 100.0 mg/L (nominal)
Details on test conditions:
- The concentration in the test assays were 100 and 20 mg per litre mineral test medium (25 and 5 mg/250 mL), respectively. 100 mg test item correspond to 305.3 mg ThOD. 20 mg test item correspond to 61.1 mg ThOD. The required amount of test item was added directly on a weight basis via Teflon discs. Subsequently, the required volume of aqueous reference stock solution (if applicable) and mineral medium were added to the vessels.
- The concentration in the test vessels with reference item (procedural control, toxicity control) was 100 mg per litre mineral test medium (25 mg/250 mL).
- A further solution containing both test and reference item at the same concentrations as in the individual solutions (test item 100 mg/L, reference item 100 mg/L) was prepared to determine the possible toxicity of the test item against the inoculum.
- Further flasks with mineral medium only were prepared for inoculum controls.
- Abiotic controls were also prepared to measure any possible abiotic degradation; a solution of the test item at about 100 mg/L was sterilized by the addition of 1 mL/L HgCl2 (10 g/L).
- In all test assays except of the abiotic controls, 2.47 mL of the inoculum stock solution were transferred for inoculation (per 250 mL) resulting in a concentration of 29.6 mg dry mass/litre (7.4 mg dry mass/250 mL).
Reference substance (positive control):
yes
Remarks:
benzoic acid, sodium salt
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Conc. based on:
test mat.
Basis for effect:
other: Results of toxicity control from ready biodegradability test 301 F
Details on results:
The biodegradation of isocetyl stearoyl stearate after 28 days of incubation in the static test was found to be 66 % (SD = 1.4 %) and 86 % (SD = 3.5 %) in the assays with 100 mg/L and 20 mg/L, respectively. The biodegradation within the 10-day-window was 43 % and 80 % in the assays with 100 mg/L and 20 mg/L, respectively. The 10-day-window started at day 3 in the assays with 100 mg/L and at day 2 - 3 in the assays with 20 mg/L.
Results with reference substance (positive control):
The reference item sodium benzoate was degraded to 86 % within the first 14 days. At the end of the test
(Day 28), the reference item was degraded by an average of 91 %.

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.
Executive summary:

At the Fraunhofer Institute for Molecular Biology and Applied Ecology the ready biodegradability of the test item was investigated according to the manometric respirometry test design and carried out according to the OECD guideline for Testing of Chemicals No. 301 F (1992) and the Council Regulation (EC) No 440/2008 of 30 May 2008. The ready biodegradability of the test item was investigated at a concentration of at a concentration of 100 mg/L (ThOD = 305 mg/L) and 20 mg/L (ThOD = 61 mg/L), respectively, in a manometric respirometry test using domestic aerobic activated sewage sludge incubated at 22°C in the dark over 28 days under continuous stirring. The biochemical oxygen demand (BOD) was measured daily and the percentage degradation was calculated from the theoretical oxygen demand (ThOD) after correcting for the BOD of inoculum controls. The biodegradation of the test item in the static test was found to be at mean 66 % with a standard deviation of 1.4 % for a concentration of 100 mg test item per liter and at mean 86 % with a standard deviation of 3.5 % for a concentration of 20 mg test item per liter after 28 days. For a concentration of 100 mg test item per liter biodegradation within the 10-day-window was found to be 43 %. For a concentration of 20 mg test item per liter biodegradation within the 10-day-window was found to be 80 %. The test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration. 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 suitability of the activated sludge.

Description of key information

NOEC (14 d) ≥ 100 mg/L for activated sludge microorganisms (OECD 301F); read-across

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

There is no study available assessing the toxicity of the target substance2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8) to activated sludge microorganisms. Therefore, read-across to the structurally related source substance Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The source substance is characterized by similar fatty acid and alcohol components and is therefore considered a suitable representative for the assessment of the ready biodegradability and toxicity of the target substance to microorganisms. A detailed justification of the analogue approach is provided in IUCLID section 13.

A ready biodegradability study conducted with the source substance Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) according to OECD guideline 301 F and GLP 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, 2017). 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 occurred within 14 days (OECD guideline 301).

The available 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 of the test item 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 % on exposure day 14, and reached an average biodegradation of 91 % at the end of the test (day 28), thus confirming suitability of the activated sludge. Hence, the test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration and a NOEC (14 d) of ≥ 100 mg/L (nominal) was derived.

Based on the structural and chemical similarity of the target and source substance, the target substance is expected to exhibit a similar ecotoxicological profile as the source substance. Therefore, it can be concluded thatthe target substance 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8) does not cause toxic effects to activated sludge microorgansims and an inhibition of degradation in sewage treatment plants is not expected.