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Environmental fate & pathways

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:
August 1, 2003 - September 4, 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, guideline test. Available as an unpublished report, acceptable without restriction.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Clinton Sanitary Wastewater Treatment Plant, Annandale, New Jersey
Activated sludge homogenised in blender (2 minutes, low speed). Allowed to settle for 60 minutes. Supernatant decanted. Supernatant, plus mineral asalt solutions, added to glass distilled water. Test medium aerated with CO2-free air for approximately 24 hours before test.
- Concentration of sludge: 10 mL sludge supernatant per liter of glass distilled water
- Mineral salt solutions (volumes per litre of glass distilled water):
-- 2.25% Magnesium sulphate solution: 1 mL/L
-- 2.75% Calcium chloride solution: 1 mL/L
-- pH 7.2 Phosphate buffer solution: 10 ml/L
-- 0.025% Ferric chloride solution: 1 mL/L
- Initial cell/biomass concentration: Microbal activity determined to be 100000 CFU/mL
Duration of test (contact time):
28 d
Initial conc.:
50.31 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Activated sludge supernatant plus minteral salts in glass distilled water
- Test temperature: 22 ± 1°C
- pH: 7.28
- pH adjusted: Buffer solution present
- Suspended solids concentration: 3.61 g/L

TEST SYSTEM
- Culturing apparatus: One litre respirometer flask
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: Aeration prior to test
- Measuring equipment: Manometric respirometer
- Test performed in closed vessels: yes
- Details of trap for CO2 and volatile organics if used: 10N NaOH as CO2 trap. Pressure reduction caused, triggering eletrolytic generation of O2 (measured with CES aerobic respirometer)

SAMPLING
none

CONTROL AND BLANK SYSTEM
Blank control and Sodium benxoate (postive control)

STATISTICAL METHODS:
Biodegration evaluation based on ThOD calculation.
Reference substance:
benzoic acid, sodium salt
Remarks:
at 50.69 mg/L
Key result
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
28 d
Results with reference substance:
93.00 (SD: 4.40) % degradation after 28 days.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance was not found to be biodegradable under the test conditions.
Executive summary:

In a GLP, OECD 301F guideline test the test substance was found to undergo 0% biodegradation after 28. The test fulfilled the validity criteria. The test substance was not found to be biodegradable under the test conditions.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, near guideline study, available as unpublished report, minor restrictions in design but otherwise adequate for assessment
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
Deviations: The test medium was aerated for 18 hours with CO2 free air for homogeneity instead of 24 hours and the activated sludge was homogenized for 3 minutes instead of 2 minutes. The protocol deviations were not believed to to have adversly affected
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not reported
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Fresh activate sludge was used as the inoculum, obtained from the Somerset-Raritan Valley sewage authority in Bridegewater, New Jersey. Domestic sewage treatment works, no known contaminants believed to be present.
Duration of test (contact time):
28 d
Initial conc.:
60 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test was conducated according to OECD guideline 301F. Test material was evaluated in triplicate test systems at a concentration of approximately 60 mg/l. The amount of oxygen taken up by the microbial populations during biodegradation of the test material, corrected for uptake by blank inoculum) is expressed as a percentage of ThOD. Biodegradation of the sodium benzoate was also measured. Duplicate blank test systems, which did not contain the test or positive control were run at the same time.
Reference substance:
benzoic acid, sodium salt
Test performance:
Test is considered valid since sodium benzoate biodegraded to approximately 97 % by day 14 and so fullfilled the guideline requirement of > 60% biodegradation within the 1st 14 days.
Parameter:
% degradation (O2 consumption)
Value:
3
St. dev.:
0.4
Sampling time:
7 d
Remarks on result:
other: Based on ThOD
Parameter:
% degradation (O2 consumption)
Value:
48.8
St. dev.:
2.2
Sampling time:
11 d
Remarks on result:
other: Based on ThOD
Parameter:
% degradation (O2 consumption)
Value:
65.5
St. dev.:
1.7
Sampling time:
13 d
Remarks on result:
other: Based on ThOD
Key result
Parameter:
% degradation (O2 consumption)
Value:
87
St. dev.:
4.2
Sampling time:
28 d
Remarks on result:
other: Based on ThOD
Details on results:
Biodegradation was calcualted as the net amount of oxygen (mg) consumed by the test system multiplied by a constant. Net amount of oxygen was calculated as the difference between the test system oxygen consumption (mg) and the average oxygen oxygen (mg) consumed by the blanks
Results with reference substance:
97 % biodegradation of sodium benzoate occured by day 14.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
87 % of initial n-pentane degraded in 28 days. N-pentane is therefore readily biodegradable
Executive summary:

The test was considered valid as 97 % degradation of sodium benzoate occured by day 14 and n-pentane was shown to be readily biodegradable with 87 % biodegradation occuring within 28 days.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
April 5th 1996 - May 3rd 1996
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study was non-GLP and non guideline, minor restrictions in design abut otherwise adequate for assessment
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
Study design was based on OECD Guideline for Testing of Chemicals, Method 301F Manometric Respirometry Test. One notable deviation from the guideline was the concentration of the test substance, which was less than the range stated in the guideline but from calculation of the ThOD for isopentane (based on OECD 301F equation) the range used was still deemed suitable. Triplicate test systems were used for the test substance and duplicates used for the control material and the blank controls.
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not reported
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum used as the source of microorganisms was an aliquot of fresh activated sludge obtained from domestic sewage works.
Duration of test (contact time):
28 d
Initial conc.:
25 - 33 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Study design was based on OECD Guideline for Testing of Chemicals, Method 301F Manometric Respirometry Test. One notable deviation from the guideline was the concentration of the test substance, which was less than the range stated in the guideline but from calculation of the ThOD for isopentane (based on OECD 301F equation) the range used was still deemed suitable. Triplicate test systems were used for the test substance and duplicates used for the control material and the blank controls.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
71.43
Sampling time:
28 d
Details on results:
The study was similar to OECD Method 301F Manometric respirometry test. The details of the ThOD of the subtance was not reported and so the suitablity of the test concentration was not clear for the report. However calculation of the ThOD of isopentane (3.6 mg/mg), using the standard equation in Annex IV of the method, did show that the concentration used did meet the criteria of at least 50 -100 mg ThOD/L specified in the guideline. % biodegradation varied between the individual replicates by >20%. However as all replicates exceeded 60 % of ThOD within the 28 day period, isopentane can be considered readily biodegradable
Results with reference substance:
Sodium benzoate: Initial concentration 51 mg/L. >60% degradation by day 14 so test could be considered valid
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
71.43 % degredation occured within 28 days and so 2-methylbutane is considered to be readily biodegradable.
Executive summary:

This followed the OECD guideline 301F manometric respirometry test with some minor deviations in test concentrations. However this deviation from the guideline were shown to not affect the integrity of the study as it meet the validity criteria. The study was therefore deemed suitable for assessment. This study indicates that isopentane is readily biodegradable.

Description of key information

There is data available for this substance. Additionally, key data is available for the structural analogues Pentane and 2-methylbutane and is presented in the dossier. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

Based on the available data, this substance is considered readily biodegradable. Key information is summarised below:

Pentane biodegraded 87% after 28 days under the conditions of the study and is therefore considered readily biodegradable.

2 -methylbutane biodegraded 71.43 % after 28 days under the conditions of the study and is therefore considered readily biodegradable.

Cyclopentane biodegraded 0% after 28 days under the conditions of the study and is therefore considered not biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information