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Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Refer to analogue justification document provided in IUCLID section 13.

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

other: BOD

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: Biodegradation toxicity control

Remarks:

source, RA-A, CAS 91050-80-5, Emery, 2007, BODIS Test

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 Jun - 10 Jul 2007

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 2012).

Qualifier:

according to guideline

Guideline:

other: Toxicity control from MARINE BODIS ISO/TC 147/SC 5/WG 4N 141

Qualifier:

equivalent or similar to guideline

Guideline:

other: Toxicity control from ISO 10708

Principles of method if other than guideline:

Unlike similar screening tests for biodegradability in freshwater systems, thismethod uses natural seawater fortified with mineral nutrients and no innoculum is added in addition to the micro-organisms already present in the seawater. Results from this test are not to be taken as indicators for ready or ultimate biodegradability but serves only to provide a preliminary level of information on ready degradability in seawater.

GLP compliance:

yes

Analytical monitoring:

no

Details on test solutions:

The test vessels are closed glass bottles with a known volume of aqueous test mixture (66.6%) and air (33.3%). They are shaken continuously to assure steady state oxygen partitioning between the aqueous and gaseous phase. The degradation is followed by weekly measurements of the BOD in the aqueous phase for a minimum 28 day period. The test vessels are re-aerated and resealed after measurement. The total oxygen uptake in the test flasks is calculated from the measured dissolved oxygen concentration divided by the saturation value at normal conditions and multiplied with the total oxygen content originally present in the aqueous and gaseous phases.

Test organisms (species):

other: natural seawater

Details on inoculum:

Unlike similar screening tests for biodegradability in freshwater systems, this method uses natural seawater fortified with mineral nutrients and no innoculum is added in addition to the micro-organisms already present in the seawater. The raw seawater used for this study was supplied by a submersible pump situated on Sutherland’s pier on the west side of Flotta in Scapa Flow. It is pumped continuously from a depth of two metres below low water spring tide level, before passing up 1.8 kilometres of plastic pipe to a 20,000 litre storage tank. Two smaller pumps move the water to three settlement tanks situated nine metres above floor level. The seawater temperature varies between 6º C in the winter and 14º C in the summer. The salinity is between 34‰ and 37‰. Five to seven days before test commencement, raw seawater passes by gravity through a 45 µm filter to the ageing tank. Collected on 06 June 2007.

Test type:

static

Water media type:

saltwater

Total exposure duration:

28 d

Nominal and measured concentrations:

Initial test substance concentration: 20 mg/L based on BOD

Details on test conditions:

TEST CONDITIONS
- Composition of medium: Natural seawater enriched with (in g/L):
KH2PO4: 8.5
K2HPO4: 21.7
Na2HPO4 x 2H2O: 29.92
NH4Cl: 0.5
CaCl2: 31.84
MgSO4 x 7H2O: 22.5
FeCl3 x 6H2O: 0.25
EDTA: 0.4
- Solubilising agent (type and concentration if used): In tests conducted with poorly soluble materials, an inert support medium is used to provide a large and controlled surface area: 1 g/bottle of chromatography silica powder containing 20 mg of ThOD/g test material/reference base fluid
- Test temperature: 19.3 - 20.2 °C
- Aeration of dilution water: yes; Saturation value for dissolved oxygen at normal atmospheric pressure: 7.45 mg/L; Total Oxygen Capacity: 26.64 mg Oxygen per test vessel

TEST SYSTEM
- Culturing apparatus: 270 (± 0.5) mL glass BOD bottles containing 180 mL test medium
- Number of culture flasks/concentration: 3
- Measuring equipment: Polarographic electrode
- Test performed in closed vessels due to significant volatility of test substance: yes


CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates
- Toxicity control: 3 replicates
- Other: support medium blank: 3 replicates

Reference substance (positive control):

yes

Remarks:

benzoic acid, sodium salt

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

other: BOD

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: Biodegradation toxicity control

Details on results:

The test item biodegraded by 94% over 28 days and showed an inhibition of -7% to seawater bacteria. The Oxygen blank and reference oil degradation were within formal and informal limits of acceptability, respectively.

Results with reference substance (positive control):

The soluble reference material, sodium benzoate, degraded by more than 60% in the first fourteen days, indicating that the seawater used in the test contained a satisfactory population of viable bacteria.

The toxicity control attained > 35% degradation after 14 days (73% after 14 d) of incubation.

"If in a toxicity test, containing both the test and the reference substance, less than 35% based on total DOC or less than 25% based on total ThOD or ThCO2 occurred within 14 days, the test substance can be assumed to be inhibitory." (OECD Guideline 301)

Since more than 25% degradation occurred in the toxicity control, the substance is with high probability not toxic to aquatic microorganisms.The test item concentration in the toxicity control of 20 mg/L BOD can be used as NOEC value for the toxicity to aquatic microorganisms.

Description of key information

NOEC (14 d) ≥ 20 mg/L BOD (natural seawater, ISO 10708, toxicity control)

Additional information

There is no study available in which the toxicity of Fatty acids, C16-18 (even numbered), esters with glycerol oligomers to microorganisms was assessed. Therefore, read-across to the structurally and chemically related source substance Fatty acids, C16-18, tetraesters with 3,3'-oxybis[1,2-propanediol] (CAS 91050-80-5) was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, section 1.5 in order to fulfill the data requirements for this substance. The source substance is characterized by similar chemical structure and is therefore considered as suitable representative for the assessment of the toxicity of the target substance to microorganism.A detailed read-across justification in provided in IUCLID section 13.

The toxicity of the source substance Fatty acids, C16-18, tetraesters with 3,3'-oxybis[1,2-propanediol] (CAS 91050-80-5) to microorganisms was investigated in a biodegradation study similar to ISO 10708 under GLP conditions. The study was performed with natural seawater as inoculum. A toxicity control included in the biodegradation study with a test item concentration of 20 mg/L BOD reached biodegradation > 35% within 14 days (76% after 14 d). Thus, the test substance is not inhibitory to aquatic microorganisms. According to ECHA Guidance R.7b (ECHA, 2017) the test item concentration can be used as NOEC value for the toxicity to aquatic microorganisms. Thus, a NOEC (14 d) of ≥ 20 mg/L BOD resulted.

Based on the available results in a biodegradation study from a structurally related read-across substance (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that the target substance Fatty acids, C16-18 (even numbered), esters with glycerol oligomers is not expected to show toxicity to microorganisms up to the limit of its water solubility (91.9 µg/L).