Glycerides, tallow sesqui-, hydrogenated, propoxylated

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study conducted between 25 and 26 November 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: RL 686/15
- Expiration date of the lot/batch: 30 October 2018
- Purity test date: Complex mixture

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature
- Stability under test conditions: No data
- Solubility and stability of the test substance in the solvent/vehicle: Low solubilty in aqueous media

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 25 mL solvent stocks in acetone prepared at nominal 100, 300, 1000, 3000 and 10000 mg/L. An aliquot of the appropriate stock solution was added to test vessels and the acetone evaporated off by nitrogen. Aliquots of RO water, synthetic sewage and activated sludge added to each test vessel, to give final volume of 500 mL per test vessel.
100 uL anti-foaming agent (silicone in oil) was also added to each test vessel (control, test item and reference substance).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Worlingworth sewage treatment works, Suffolk, UK
- Preparation of inoculum for exposure:
- Pretreatment: Maintained under aerobic conditions
- Initial biomass concentration:

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

No data

Test temperature:

20 +/- 2 oC (nominal)
20.3 - 21.4 oC (measured)

pH:

7.51 - 8.29 (measured)

Dissolved oxygen:

Initial DO (mg O2/L)
Control: 5.7 - 6.4
Test item: 5.2 - 6.7
Reference item: 6.5 - 8.2

Salinity:

No data

Conductivity:

No data

Nominal and measured concentrations:

10, 30, 100, 300 and 1000 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL bottles
- Type (delete if not applicable): closed
- Material: Glass
- Fill volume: 500 mL
- Aeration: Test vessels aerated and stirred for duration of test (3 hours)
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per abiotic control (replicates): 1
- Sludge concentration (weight of dry solids per volume): 1.6 g/L MLSS (mixed liquor suspended solides)
- Nutrients provided for bacteria: Synthetic sewage
- Nitrification inhibitor used (delete if not applicable): None

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: RO water

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Test concentrations: 10, 30, 100, 300 and 1000 mg/L (nominal)

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

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: Insoluble test item was noted coating surfaces during test and may potentially have interferred with transfer of oxygen across DO probe. Therefore, effect may not be due to toxicty of test item.

Details on results:

- Coefficient of variation of oxygen uptake rate in control replicates: 7.3%

Results with reference substance (positive control):

- Results with reference substance valid?: Yes
- Relevant effect levels: EC50 for 3,5-DCP was 8.94 mg/L (nominal)

Nominal test concentration	Mean respiration rate	% inhibition
(mg/L)	(mg O2/g/h)
Control
0	32.6	-
Test item
10	28.5	13
30	26.3	19
100	27.5	16
300	22.2	32
1000	25.0	24
Reference item
3	25.2	23
10	15.4	53
32	6.5	80

Validity criteria fulfilled:

yes

Conclusions:

The mean respiration rate of the control was 32.6 mg O2/g/h with a coefficient of variation of 7.3% (max. permitted = 30%)
3-hour EC50 for reference item (3,5 -DCP) was 8.94 mg/L, indicating the activated sludge was sensitive to inhibition (EC50 range allowed = 2 -25 mg/L).
The mean respiration rate of activate sludge exposed to the test item did not show a concentration related response with % inhibition of 13, 19, 16, 32 and 24% at nominal test item concentrations of 10, 30, 100, 300 and 1000 mg/L, respectively. Consequently it was not possible to determine EC20, EC50, EC80 and 95% effect concentrations. Potential inhibition (>20%) was observed at 300 and 1000 mg/L, suggesting a NOEC of 100 mg/L (nominal). However, during the test it was noted that insoluble test item was coating surfaces and potentially interferring with transfer of oxygen across the dissolved oxygen probe. The test substance is not toxic to aquatic organisms at the limit of solubility, which is was less than the LoQ.

Executive summary:

A study was performed to determine the effects of the test item on sewage treatment micro-organisms by measuring the rate of oxygen uptake of activated sludge under aerobic conditions. The test was conducted according to the principles of GLP and followed internationally accepted test guidelines.

Test validity criteria were met, therefore, the test can be considered valid. Test item NOEC was determined to be 100 mg/L, however, during the test it was noted that insoluble test item was coating surfaces and potentially interferring with transfer of oxygen across the DO probe, making it difficult to determine if inhibition observed was due to toxicity of the test item. It is concluded that the test substance is not toxic to aquatic organisms at the limit of solubility, which is was less than the LoQ.

Description of key information

A study was performed to determine the effects of the test item on sewage treatment micro-organisms by measuring the rate of oxygen uptake of activated sludge under aerobic conditions. The test was conducted according to the principles of GLP and followed internationally accepted test guidelines. Test validity criteria were met, therefore, the test can be considered valid.

EC20, EC50, EC80 and 95% confidence intervals could not be estimated for the test item as there was no concentration response relationship

Test item NOEC was determined to be 100 mg/L. However, during the test it was noted that insoluble test item was coating surfaces and potentially interferring with transfer of oxygen across the DO probe, making it difficult to determine if inhibition observed was due to toxicity of the test item.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L