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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:
1994-09-08 to 1994-10-07
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): WITAMOL 118
- Substance type: product
- Physical state: liquid
- Stability under test conditions: no data
- Storage condition of test material: no data
- Other: none
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: domestic sewage plant (Marl-East, Germany)
- Laboratory culture: no
- Storage conditions: not mentioned
- Storage length: not mentioned
- Preparation of inoculum for exposure: according to prescipt (not specified)
- Pretreatment: not mentioned
- Concentration of sludge: 25.3 mg/L suspended solids; dry weight of inoculum: 4.22 g/L
- Initial cell/biomass concentration: 55x10E4 cfu/mL (colony forming units/ml)
- Water filtered: not mentioned
Duration of test (contact time):
29 d
Initial conc.:
20.1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: not specified
- Additional substrate: none
- Solubilising agent (type and concentration if used): not used
- Test temperature: 20.8 - 22.1 °C
- pH: 6.6 - 6.7
- pH adjusted: no
- Aeration of dilution water: not specified
- Suspended solids concentration: 25.3 mg/L
- Continuous darkness: not mentioned
- Other: none

TEST SYSTEM
- Culturing apparatus: 5000 ml glass vessels containing culture samples
- Number of culture flasks/concentration: 2 bottles, one concentration
- Method used to create aerobic conditions: not mentioned
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: carbon analyzer (Shimadzu)
- Details of trap for CO2: collection of carbon dioxide as sodium carbonate with sodium hydroxide solution (no further details mentioned)
- Other: none


SAMPLING
- Sampling frequency: on days 0, 1, 4, 8, 13, 18, 21, 26, 28 and 29
- Sampling method: not mentioned
- Sample storage before analysis: not mentioned
- Other: none


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (2 vessels with inoculum without test substance)
- Abiotic sterile control: not performed
- Toxicity control: not performed
- Other: none


STATISTICAL METHODS: no statistics performed
Reference substance:
benzoic acid, sodium salt
Remarks:
25 mg/l final test medium (14.6 mg DOC/l)
Preliminary study:
not performed
Test performance:
Procedure: The test substance was given into a defined, liquid mineral medium, which was inoculated with an inoculum from activated sludge and aerated at 20.8 - 22.1 °C. The released CO2 is bound in caustic soda solution in the form of sodium carbonate. The degradation was followed over the duration of the test of 29 days at the days of sampling as stated above via a TIC analysis (total inorganic carbon) of the bound CO2. One day before the end of the test (28th day) a pH-measurement was conducted and the remaining dissolved CO2 was driven out by acidification of the test preparation, the degradation values ascertained on the 29th day (end of incubation) are therefore related to the 28th day.
Preparation of the mineral medium: Two days before the beginning of the test (addition of the test substance) 35 L of the mineral medium were prepared and aerated overnight. On the following day 2400 mL were filled into the individual test containers and, after inoculation with the inolculum, filled with the mineral medium up to 3 L.
Dosage of the test material: The test material was weighed exactly by means of a weighing aid (reaction vessel from Eppendorf, cut-off cover) and was put into the test vessels together with the weighing aid.
Parameter:
% degradation (CO2 evolution)
Value:
ca. 76
Sampling time:
29 d
Remarks on result:
other: after acification
Details on results:
see below
Results with reference substance:
see below

Table: Degradation kinetic

 sampling time [days]  degradation [%]         
   test substance        reference substance
  vessel 1  vessel 2  mean  
1 0 0 0 21
 4 0 0 0 66
8 46 36 41 74
 13  64  55  60  75
 18  73  66  70  76
 21  77  71  74  78
 26  80  74  77  77
 28  81  72  77  76
 29 (after acifidation)  80  72  76  76
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Executive summary:

After 28 d 76 % was biodegradaded. The 10 -day window is reached because during 10 d > 60 % was biodegradaded. Therefore 1,2-Benzenedicarboxylic acid, di-C8-10-alkyl esters is regarded as readily biodegradable.

Description of key information

Biodegradation: Readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

The biodegradability of 1,2 -Benzenedicarboxylic acid, di-C8 -10 -alkylesters was studied in a biodegradation study according to OECD 301B. A biodegradation of 76 % was reached after 28 days. The 10 -day window criterion was met. Therefore 1,2-Benzenedicarboxylic acid, di-C8-10-alkyl esters is considered readily biodegradable.

Several studies with structurally related materials (e.g. linear C6-C10 and linear C11 phthalate) support the result.

Supporting these findings, the biodegradation prediction for the isomers based on BIOWIN v4.11 models (1 -6) is ready biodegradability.

A known shortcoming of these predictions is the fact that BIOWIN does not consider steric factors or low solubility, which might limit an enzyme’s ability to access otherwise labile bonds. Nevertheless, the predictions indicate that the isomers of 1,2-Benzenedicarboxylic acid, di-C8-10- alkyl ester based on their fragments can undergo rapid degradation. The BIOWIN predicted biodegradation potential can be considered as an indication of potential degradation and as supporting information for the purpose of the risk assessment.