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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 December 2012 to 07 February 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Read-across performed with structurally similar substance.
Reason / purpose for cross-reference:
other: read-across target
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): local wastewater treatment plant (ARA Ergolz II, Füllinsdorf / Switzerland) treating predominantly domestic sewage.

- Preparation of inoculum for exposure:
* sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted.
* a homogenised aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.
* during the holding period of one day prior to use, the sludge was aerated at room temperature.
* prior to use, the sludge was diluted with test water to a concentration of about 1 g dw/L.
* defined volumes of this diluted activated sludge were added to test water to obtain a final concentration of 30 mg dw/L.
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of the medium: according to the OECD guideline
- Test temperature: 21 to 24°C.
- pH: Prior to test start (Day 0), the pH was measured in each test flask after the addition of test and/or reference item and adjusted to 7.3 with a 1M sodium hydroxide solution.
- pH adjusted: yes
- Suspended solids concentration: not reported
- Continuous darkness: yes. The test vessels were incubated in a dark room

TEST SYSTEM
- Culturing apparatus: 5-litre all-glass amber bottles
- Number of culture flasks/concentration: Two absorber flasks, the first one containing 300 mL 0.05 M NaOH and the second one containing 200 mL 0.05 M NaOH.
- Measuring equipment: TOC analyser
- Test performed in closed vessels due to significant volatility of test substance: No
- Test performed in open system: yes

SAMPLING
- Sampling frequency: samples were taken on Exposure Day 2, 5, 7, 9, 12, 14, 19, 21, 28, and 29.
- Sampling method: an aliquot of 5.0 mL was withdrawn from the absorber flask nearest to the test flask for analysis of inorganic carbon. Additional samples for analysis of IC were withdrawn from the second absorber flask of all test vessels on Exposure Day 14 and at the end of the exposure period on Exposure Day 28 in order to correct for any carry over of CO2.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes

Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
77
Sampling time:
28 d
Details on results:
The CO2 formation of the test material, Lanthanum Acetate, in the test media significantly increased from the start of the test until Exposure Day 19, when the mean biodegradation reached 75%. At the end of the 28 day exposure period, average biodegradation was 77%.
Toxicity control: > 25% degradation after 28 days, confirming that test material was not toxic to the microorganisms in the test.
Results with reference substance:
By the end of the test (Exposure Day 28), average biodegradation was 90 %.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
A CO2 evolution test (OECD 301B) demonstrated that the test material, lanthanum acetate, is readily biodegradable, passing the 10-d time window criterium (pass level = 60%). It must be kept in mind that this refers to the organic part of the molecule (acetate), since La itself is not biodegradable (endpoint not relevant for inorganic part of substance). The results of the test can be considered reliable without restrictions.
Executive summary:

The ready biodegradability of the test material was determined in accordance with the standardised guideline OECD 301B, under GLP conditions.

A CO2 evolution test (OECD 301B) demonstrated that the test material, lanthanum acetate, is readily biodegradable (77%), passing the 10-d time window criterium (pass level = 60%). It must be kept in mind that this refers to the organic part of the molecule (acetate), since La itself is not biodegradable (endpoint not relevant for inorganic part of substance).

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted on read-across material
Justification for type of information:
Read-across performed with structurally similar substance.
Reason / purpose for cross-reference:
read-across source
Key result
Parameter:
% degradation (CO2 evolution)
Value:
77
Sampling time:
28 d

Description of key information

Read-across performed with structurally similar substance.

A CO2 evolution test (OECD 301B) demonstrated that the test material, lanthanum acetate, is readily biodegradable (77%), passing the 10-d time window criterium (pass level = 60%). It must be kept in mind that this refers to the organic part of the molecule (acetate), since La itself is not biodegradable (endpoint not relevant for inorganic part of substance).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Read-across performed with structurally similar substance.

The ready biodegradability of the test material was determined in accordance with the standardised guideline OECD 301B, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

A CO2 evolution test (OECD 301B) demonstrated that the test material, lanthanum acetate, is readily biodegradable (77%), passing the 10-d time window criterium (pass level = 60%). It must be kept in mind that this refers to the organic part of the molecule (acetate), since La itself is not biodegradable (endpoint not relevant for inorganic part of substance).