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Toxicity to microorganisms

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Endpoint:
toxicity to microorganisms
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 provided in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
GLP compliance:
yes
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 14.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Result of toxicity control from ready biodegradability test
Remarks on result:
other:
Remarks:
Source: Key, source, RA-A, CAS 93803-87-3, Croda, 1998, CO2 evolution, RL2
Conclusions:
The retained effect concentration for the toxicity to microorganisms is a NOEC (14 d) of ≥ 14.2 mg/L (nominal, OECD 301 B, read-across).
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data based on the inhibition 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 2017).
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: After addition of 10 mL MilliQ Water to each weighing bottle containing the test substance, followed by thorough mixing (vortex) and ultra sonication (20 min), the resulting emulsions with test substance at the surface were quantitatively added to the test media. The test solutions were continuously stirred during the test. Two days later no test substance was observed at the surface of the test medium.
- Eluate: no
- Controls: yes
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source of inoculum/activated sludge: Obtained from a municipal sewage treatment plant ‘Waterschap de Maaskant’, ‘s-Hertogenbosch, The Netherlands.
- Laboratory culture: No
- Storage conditions: The sludge was kept under continuous aeration until further treatment.
- Preparation of inoculum for exposure: Before use, the sludge was allowed to settle for at least 30 minutes and the liquid decanted for use as inoculum at the amount of 10 mL/L of mineral medium.
- Concentration of sludge: Suspended solid concentration was 5.1 g/L
- Water filtered: No
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
14 d
Test temperature:
20 - 22 °C
pH:
7.4 - 7.6
Details on test conditions:
TEST SYSTEM
- Test vessel: 2 L all-glass brown coloured bottles
- Aeration: A mixture of oxygen (21%) and nitrogen (79%) was led through a bottle, containing 0.5 – 1 L 0.0125 M Ba(OH)2 solution to trap CO2. The CO2-free air was sparged through the scrubbing solutions at a constant rate. During incubation the rate was 1-2 bubbles/sec (ca. 30 - 100 mL/min)
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per toxicity control: 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: According to OECD Guideline 301B using tap-water purified by reverse osmosis and subsequently passed over activated carbon and ion-exchange cartridges.

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED: biodegradation based on CO2 evolution in the toxicity control
Reference substance (positive control):
yes
Remarks:
benzoic acid, sodium salt
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 14.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Result of toxicity control from ready biodegradability test
Results with reference substance (positive control):
The reference substance attained 78.1% degradation after 14 d and 89% degradation after 28 d, respectively.

The toxicity control attained 56.3% degradation after 14 d of incubation. 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 14.2 mg/L can be used as a NOEC value for the toxicity to aquatic microorganisms.

Description of key information

NOEC (14 d) ≥ 14.2 mg/L for activated sludge microorganisms (OECD 301 B)

Key value for chemical safety assessment

Additional information

There is no respiration inhibition study available, in which the toxicity offatty acids, C14-22, C16-24-alkyl esters (CAS 92797-30-3)to activated sludge microorganisms was assessed. Therefore, read-across to the structurally related source substance2-octyldodecyl isooctadecanoate(CAS 93803-87-3) was conducted in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5 for which a standard ready biodegradability test according to OECD guideline 301 B 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 degraded well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration. 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 d (OECD 301).

The available ready biodegradability test included a toxicity control containing 14.2 mg/L test material and 39.85 mg/L reference material. The toxicity control attained 78.1% degradation after 14 d of incubation. Hence, the substance is not toxic to aquatic microorganisms and a NOEC of ≥ 14.2 mg/L was derived.

Based on the structural and chemical similarity of the target and source substance, the target substance is expected to have a similar ecotoxicological profile as the source substance. Therefore, it can be concluded that the target substancefatty acids, C14-22, C16-24-alkyl esters (CAS 92797-30-3)does not inhibit the degradation process in sewage treatment plants.