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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27 July 1990 - 24 August 1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
the results of this key study are compiled in a summary report only representing the most crucial results, lacking information on the blanks and reference substance. Raw data should be available.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
- ferric chloride stock solution was 0.25g not 0.2g. The slight difference in composition of the mineral salts medium was trusted to have no effect on the results.
Principles of method if other than guideline:
The study was conducted in accordance to draft Ecotoxicology SOP 158 01. However, the EDTA stock solution contained 0.4g (as recommended in the 1988 OECD Ring Test) and not 0.5g as advised by the draft SOP 158 01.
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
other: Secondary effluent from an unacclimatised activated sludge plant
Details on inoculum:
- Source of inoculum/activated sludge: Secondary effluent from an unacclimatised activated sludge plant at URL North
- Preparation of inoculum for exposure: 10% by volume of activated sludge plant secondary effluent was filtered through Whatman filter paper (541) to remove coarse particulate matter.
- Pretreatment: The level of dissolved inorganic carbon (DIC) was reduced by sparging the filtered effluent with nitrogen after prior adjustment of the pH to 6.5.
Duration of test (contact time):
28 d
Initial conc.:
9.4 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral salts medium (as recommended in the 1988 OECD Ring test)
- Test temperature: Air temperature 18-21°C; Temperature in the liquid medium 21.5-23°C
- pH: 6.5
- pH adjusted: yes
- Other: EDTA stock solution (for the preparation of the mineral salts medium) contained 0.4g instead of 0.5g as recommended in the draft Ecotoxicology SOP 158 01; Nominal Carbon added to medium: 940 µg (assuming 100% purity of compound)

TEST SYSTEM
- Culturing apparatus: 160mL vessels (hypovials) containing 100mL mineral salts medium inoculated with secondary effluent and the respective test of reference substance
- Method used to create aerobic conditions: headspace of vessels filled with air (60mL), containing approx. 6 times the mass of oxygen required for the complete oxidation of the substance.
- Measuring equipment: Ionics 555 Inorganic Carbon Analyser for measurement of CO2/DIC (headspace gas and liquid medium)
- Test performed in closed vessels due to significant volatility of test substance: yes

SAMPLING
- Sampling frequency: Day 4, 7, 11, 14, 18, 21, 25 and 28
- Sampling method: At each interval a vessel is removed and the carbon dioxide concentration of the headspace gas determined. The seal of the vessel is then broken and the concentration of inorganic carbon in the test medium measured.

CONTROL AND BLANK SYSTEM
There are no reference substance and blank controls included in the report, however the report contains relevant summary data for 10 fragrance ingredients, including Litsea cubeba. The test was part of a screening of a range of fragrances of the same functional chemistry.
Key result
Parameter:
% degradation (CO2 evolution)
Value:
103.9
Sampling time:
28 d
Remarks on result:
other: Given the allowed error in biodegradation studies of ±20% it is regarded as applicable to interpret the 103.9% for Litsea cubeba as 100% biodegradation.
Validity criteria fulfilled:
not specified
Remarks:
no information on difference between replicates and CO2 evolution in blank, toxicity control not applicable as substance was found to be readily biodegradable.
Interpretation of results:
readily biodegradable
Conclusions:
As part of a screening test of a range of same functional chemicals, Litsea cubeba essential oil can be regarded as readily and ultimately biodegradable, with a relatively high percentage biodegradation in comparison to other substances tested.
Executive summary:

The performed sealed vessel test is a CO2 production test according to OECD Guideline 301B. The test was suitable to determine the ready and ultimate biodegradability of Litsea cubeba essential oil. Unilever Research compiled a summary report presenting the ready biodegradability results of the substance Litsea cubeba essential oil within a group of 10 other substances, all possessing a similar chemical functionality and thus resulting in the omission of a reference substance and blank controls during the test performance.

A biodegradation rate of nearly 104% on day 28 for Litsea cubeba essential oil results in a classification as readily biodegradable.

Description of key information

The performed sealed vessel test is a CO2 production test according to OECD Guideline 301B. The test was suitable to determine the ready and ultimate biodegradability of Litsea cubeba essential oil. Unilever Research compiled a summary report presenting the ready biodegradability results of the substance Litsea cubeba essential oil within a group of 10 other substances, all possessing a similar chemical functionality and thus resulting in the omission of a reference substance and blank controls during the test performance. A biodegradation rate of nearly 104% on day 28 for Litsea cubeba essential oil results in a classification as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information