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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:
31-0ct-2011 to 30-Nov-2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
Version dated 17.07.92
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Lot-No.: 20980
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Source: activated sludge from the sewage plant at Taunusstein-Bleidenstadt
Treatment: washed twice with mineral nutrient solution to eliminate organic components and carbonates from the sludge. Sunsequently, aerated by means of compressed humidified air for about four hours.
Before use the sludge was homogenised at low speed for 2 minutes and then filtered through a cotton filter previously carefully rinsed with deionised water.
The filtrate was used as inoculum (1 % of the final volume of the test solution) on the same day of preparation.
Duration of test (contact time):
29 d
Initial conc.:
14 mg/L
Based on:
test mat.
Initial conc.:
10 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Test vessels: 5-litre amber carboys closed with stoppers with tubing for gas inlet and outlet (gas exit line)
Before starting the test: the mineral nutrient solution with inoculum but without test article aerated for 24 hours with CO,-free compressed air to purge the system of carbon dioxide.
After the test was started by addition of the test item, the gas outlet (exit air line) was connected to at least three CO2 absorber bottles filled with 100 ml 0.025 N Ba(OH), (connection in series), and bubbling of CO2 free compressed air through the solution was continued.
Periodically the CO2 absorber nearest the test vessel was removed for analysis, and replaced by a new CO2 absorber at the far end.
Precipitation of BaC03 in the second CO2 trap indicated that the absorber bottle nearest the test vessel had to be changed and analysed for CO2.
Titrations were performed on day 3, 6, 10, 15, 21, 28, and 29·
CO2 measurement: CO2 generated by the test item was trapped by 0.025 N Ba(OH)2 in a trap system described in the Guideline.
Remaining Ba(OH)2 (0.025 N) in the CO2 trap removed from the trap system was quantified by titrating with HCI (0.05 N) using phenolphthalein as an indicator. Each millilitre HCI of difference between the blank control and the test series with the test item titrated corresponds to 1.1 mg of CO2 produced. Hence, CO2 production in test item solutions were corrected for the mean values from titration of two parallel Blank solutions.
Degradation was calculated as a percentage of the theoretical CO2 ("% TCO/) produced by complete combustion of the test item.
The results of the degradation were followed graphicallyalues of titration for the 'Blank'
Preliminary study:
Not applicable
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 70 - <= 73
Sampling time:
28 d
Details on results:
The "10-days-window", as required by the OECD guideline 301 B was met, but is not regarded, as the test item is a polymeric surfactant with a typical chain-distribution and not a pure substance. Thus, the test item may be regarded as "readily biodegradable". The total COrevolution of the Blank was 107.6 mg CO2/ 3.5 litres of test solution.
Results with reference substance:
The control item sodium benzoate was degraded 81%, the "10-days-window" being met within 10 days (73%). The results obtained with the toxicity control indicate that there was no toxicity of the test item towards microorganisms at the concentration used within the test.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item may be regarded as "readily biodegradable".

Description of key information

Dodecyl lactate proved to be readily biodegradable in an aerobic degradation screening test.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Supporting tests with other alkyl lactates or long chain alcohols confirm the high potential for biodegradation of all constituents in the product for registration.