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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: Ready Biodegradability (Closed Bottle test) OECD 301D
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: A0076
- Expiration date of the lot/batch: 2021


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Ambient, in the dark
- Stability under test conditions: Stable
- Solubility and stability of the test substance in the solvent/vehicle: Stable

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test material was stated to be poorly soluble in water therefore a non-ionic surfactant (IGEPAL CA 630) was used to emulsify the sample.

- Final dilution of a dissolved solid, stock liquid or gel: The emulsion was gradually diluted by the addition of deionised water and then made up to volume (500ml) to give a concentration of 1.02g/l. Replicate BOD bottles were filled to absolute volume (250ml) with the test solution, prepared by addition of a 2ml/l sample stock solution to 3.5L of inoculated mineral medium to give a test concentration of 2.0mg/l.

FORM AS APPLIED IN THE TEST (if different from that of starting material) : solution


Analytical monitoring:
no
Vehicle:
yes
Remarks:
non-ionic surfactant (IGEPAL CA 630)
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test material was stated to be insoluble in water therefore a surfactant was used to emulsify the sample. To prepare the emulsion, 0.5008g of the test item was intimately mixed with a 0.2496g of nonionic surfactant (IGEPAL CA 630). The emulsion was gradually diluted by the addition of
deionised water and then made up to volume (500ml) to give a concentration of 1.02g/l.
- Controls:
- Inoculum blank: inoculated mineral medium
- Functional/reference control: 5.01 mg/L sodium acetate
- Toxicity control: 2.0 mg/L test Item and 5.01 mg/L reference Item (sodium acetate)
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): IGEPAL CA 630 (synonym: Octylphenoxy poly(ethyleneoxy)ethanol, branched)
- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): 1.00 mg/L
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): Not reported
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Laboratory culture: no
- Name and location of sewage treatment plant where inoculum was collected: Cambridge STW, Cowley Road, Cambridge
- Initial biomass concentration: 1 ml/l
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
28 d
Hardness:
Not reported
Test temperature:
20.3 - 20.5oC
pH:
Not reported
Dissolved oxygen:
Control vessels
Day 0: 8.20 -8.26 mg/L
Day 7: 8.22 - 8.08 mg/L
Day 17: 7.17 - 7.87 mg/L
Day 28: 5.75 - 7.86 mg/L
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations:
- Functional/reference control: 5.01 mg/L sodium acetate
- Toxicity control: 2.0 mg/L test Item and 5.01 mg/L reference Item (sodium acetate)
Details on test conditions:
TEST SYSTEM
- Test vessel: 250ml BOD bottles
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: filled to absolute volume
- Biomass loading rate: 1mL/L
- Aeration: mineral medium was aerated for 20 minutes and allowed to stand for 23 hours
- No. of vessels per concentration (replicates): 11 vessels
- No. of vessels per control (replicates):11 vessels
- No. of vessels per vehicle control (replicates): 11 vessels
- No. of vessels per abiotic control (replicates): 11 vessels

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: mineral medium prepared according to OECD 301D guideline

OTHER TEST CONDITIONS
- Adjustment of pH: not reported
- Photoperiod: The bottles were incubated in the dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : dissolved oxygen measurements were used to determine material toxicity by comparing the biochemical oxygen demand (BOD) results of the test and reference vessels with that of the toxicity control vessels. The percentage degradation of the toxicity control was calculated based on the biological oxygen demand recorded. This was compared to the test and reference solutions used to make up the toxicity sample.
Reference substance (positive control):
yes
Remarks:
sodium acetate
Duration:
17 d
Dose descriptor:
NOEC
Effect conc.:
2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: degradation of the reference material in the toxicity control conducted as a part of the biodegradation study (OECD 301D)
Results with reference substance (positive control):
For the reference material, sodium acetae, 88% degradation was observed after 17 days of incubation.
Validity criteria fulfilled:
yes
Remarks:
For sodium acetate 99% degradation was observed after 28 d (must be at least 60%). The maximum blank DO loss was 0.40 mg/l (must not exceed 1.5 mg/l after 28 d).
Conclusions:
The test item is not inhibitory to sewage treatment microorganisms at tested concentration of 2.0 mg/L.
Executive summary:

The toxicity of the test item to activated sewage sludge was taken from the toxicity control of a GLP-compliant ready biodegradability Closed bottle test following OECD guideline 301D (Crane 2018). The results of the study show that the test item is not inhibitory to sewage treatment microorganisms at tested concentration of 2.0 mg/L. The NOEC of test item to aquatic microorganisms is 2.0 mg test item/L.

The study was conducted according to the standard guideline and is GLP-compliant, therefore is considered reliable and suitable for this endpoint.

Description of key information

The NOEC of test item to aquatic microorganisms is 2.0 mg test item/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
2 mg/L

Additional information

The toxicity of the test item to activated sewage sludge was taken from the toxicity control of a GLP-compliant ready biodegradability Closed bottle test following OECD guideline 301D (Crane 2019). The results of the study show that the test item is not inhibitory to sewage treatment microorganisms at tested concentration of 2.0 mg/L.The NOEC of test item to aquatic microorganisms is 2.0 mg test item/L.

The study was conducted according to the standard guideline and is GLP-compliant, therefore is considered reliable and suitable for this endpoint.