Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental start date: 15 February 2016; Experimental completion date: 14 March 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Version / remarks:
2014
Qualifier:
according to
Guideline:
ISO 14593:1999 (Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium - Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test))
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Source and lot/batch No. of test material: 409020
- Expiration date of the lot/batch: 05 January 2017
- Purity: 99.7%
- Storage condition of test material: room temperature in the dark
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: secondary treatment stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK

- Storage length: prepared the same day collected

- Preparation of inoculum for exposure: The effluent was filtered through coarse filter paper. The inorganic carbon content of the inoculum was reduced by sparging the filtrate with CO2-free air.
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
IC (inorganic carbon)
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium that recommended in the OECD and ISO Guidelines.
- Test temperature: 20 ± 1.0 °C
- Aeration of dilution water: Supernatant was maintained on aeration using CO2-free air until use
- Suspended solids concentration: not reported
- Continuous darkness: yes/no

TEST SYSTEM
- Culturing apparatus: 125 mL glass Wheaton bottles
- Number of culture flasks/concentration: 38 replicate vessels
- Method used to create aerobic conditions: aeration of supernatant prior to study and headspace to liquid ratio of 1:2
- Measuring equipment: Headspace was injected into the Inorganic Carbon channel of a Shimadzu TOC-Vcsh TOC analyser
- Test performed in closed vessels due to significant volatility of test substance: Yes, all vessels sealed using Teflon lined silicon septa and aluminium crimp caps
- Details of trap for CO2: An aliquot (1.0 mL) of concentrated orthophosphoric acid was injected through the septum of each vessel taken for analysis in order to lower the pH of the medium to< 3. The vessels were then shaken at approximately 150 rpm for 1 hour at 20±1 °C prior to samples being withdrawn from the headspace and analysed for inorganic carbon.

SAMPLING
- Sampling frequency: Triplicate inoculum control, procedure control and test item vessels were sacrificed on Days 0, 3, 7, 9, 11, 14, 16 and 21 for IC analysis. On day 28, five replicate vessels were sacrificed for IC analysis. Triplicate toxicity control vessels were sacrificed on Days 0, 7 and 14 for IC analysis.

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated culture medium
- Toxicity control: test item plus reference item in culture medium, to give a final concentration of 40 mg C/L, 9 replicate vessels
Reference substance:
benzoic acid, sodium salt
Test performance:
Variation in the biodegradation rates obtained on different sampling days was considered to be the result of normal biological variation between the respiration rates of replicate vessels. Due to the sacrificial nature of the study design, the biodegradation rates obtained on each sampling occasion were for individual replicate vessels and not the result of cumulative biodegradation values determined from a single vessel sampled on numerous occasions and as such variation in biodegradation rates on different sampling days was to be expected.
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
3 d
Parameter:
% degradation (CO2 evolution)
Value:
9
Sampling time:
7 d
Parameter:
% degradation (CO2 evolution)
Value:
12
Sampling time:
9 d
Parameter:
% degradation (CO2 evolution)
Value:
14
Sampling time:
11 d
Parameter:
% degradation (CO2 evolution)
Value:
18
Sampling time:
14 d
Parameter:
% degradation (CO2 evolution)
Value:
16
Sampling time:
16 d
Parameter:
% degradation (CO2 evolution)
Value:
19
Sampling time:
21 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
22
Sampling time:
28 d
Details on results:
The mean total inorganic carbon in the inoculum control vessels on Day 28 was 0.60 mg/L; equivalent to 3% of the organic carbon added initially as test item to the test vessels and therefore satisfied the validation criterion given in the Test Guideline.

The toxicity control attained 50% biodegradation after 14 days thereby confirming that the test item did not exhibit an inhibitory effect on the sewage treatment micro-organisms used in the test.

The test item was shown to fairly quickly form the degradant, octafluoropentanol (CASRN 355-80-6). It was considered that the test item that did not degrade to octafluoropentanol was suspected to have broken down to form methacrylic acid which was not analytically measured due to the amount formed being below the limit of quantification (50 mg/L). The methacrylic acid was considered to have mineralized with CO2 evolution shown by the inorganic carbon analyses.

The results from chemical analysis on Day 0 gave measured concentrations of 47.9 and 48.2 mg/L of the parent test item (OFPMA), equivalent to 86 and 87% of nominal for test item replicates R1 and R2 respectively. The degradation product octafluoropentanol gave values of less than the limit of quantitation (0.0523 mg/L) on Day 0.

On Day 14 measured concentrations of the parent test item (OFPMA) had reduced to 3.98 and 13.3 mg/L (equivalent to 7 and 24% of nominal respectively) with concentrations of the measured degradant, octafluoropentanol of 33.8 and 25.2 mg/L respectively for test item replicates R1 and R2.

At the end of the study on Day 28 measured concentrations of the parent test item (OFPMA) had reduced to less than the limit of quantitation (0.0494 mg/L) for test item replicate R1 and 3.14 mg/L for test item replicate R2 (equivalent to 0 and 6% of nominal) with concentrations of the measured degradant, octafluoropentanol of 34.5 and 35.9 mg/L respectively for test item replicates R1 and R2.
Results with reference substance:
Sodium benzoate attained 72% biodegradation after 14 days and 65% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:

The test item (octafluoropentyl methactylate) attained 22% biodegradation after 28 days by inorganic carbon analysis and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 310.
 
The test item was shown to fairly quickly form the degradant, octafluoropentanol. It was considered that the test item that did not degrade to octafluoropentanol was suspected to have broken down to form methacrylic acid which was not analytically measured due to the amount formed being below the limit of quantification (50 mg/L). The methacrylic acid was considered to have mineralized with CO2 evolution shown by the inorganic carbon analyses.
Executive summary:

The assessment of ready biodegradability was performed according to the GLP-complaint study following OECD Guideline 310. This OECD guideline was selected as the preliminary work showed that the test item was volatile and the OECD Guideline 310 method is recommended for volatile materials.

 

The OFPMA (20 mg C/L) was exposed to non-adapted activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at 20 ± 1.0 °C for 28 days. The degradation was assessed by determination of carbon dioxide evolution on Days0, 3, 7, 9, 11, 14, 16, 21, and 28.

 

Compound specific analyses with GC/MS assessment were carried out on Days 0, 14 and 28 from duplicate test item and inoculum control vessels.

 

The toxicity control attained 50% degradation after 14 days thereby confirming that the test item was not toxic to the inoculum. The sodium benzoate attained 72% degradation at 14 days thereby confirming the suitability of the inoculum and test conditions. The test item attained 22% degradation after 28 days and therefore cannot be considered to be readily biodegradable.

 

The test item (OFPMA) was shown to fairly quickly form the degradant, octafluoropentanol (CAS 355-80-6). It was considered that the test item that did not degrade to octafluoropentanol was suspected to have broken down to form methacrylic acid which was not analytically measured due to the amount formed being below the limit of quantification (50 mg/L). The methacrylic acid was considered to have mineralized with carbon dioxide evolution shown by the inorganic carbon analyses.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Version / remarks:
2006
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: secondary treatment stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK

- Preparation of inoculum for exposure: The sample of effluent was filtered through coarse filter paper (first approximate 200 ml discarded).

- Pretreatment: In order to reduce the inorganic carbon (IC) content of the inoculum, the filtrate was sparged with CO2-free air for approximately 1 hour whilst maintaining its pH at 6.5 using concentrated orthophosphoric acid. After sparging, the pH was restored to its original value of 7.19 using 7 M sodium hydroxide and the inoculum allowed to settle for approximately 1 hour prior to removal of an aliquot (2 litres) of the supernatant for use in the test. The supernatant was maintained on aeration using CO2-free air until use.
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
IC (inorganic carbon)
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral salts medium as per OECD Guideline 310
- Test temperature: 20 ± 1 °C
- Aeration of dilution water: The supernatant was maintained on aeration using CO2-free air until use
- Suspended solids concentration: not reported
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 125 mL glass Wheaton bottles
- Number of culture flasks/concentration: 29 replicate vessels
- Method used to create aerobic conditions: aeration of supernatant prior to study and headspace to liquid ratio of 1:2
- Measuring equipment: Headspace was injected into the Inorganic Carbon channel of a Shimadzu TOC-Vcsh TOC analyser
- Test performed in closed vessels due to significant volatility of test substance: Yes, all vessels sealed using Teflon lined silicon septa and aluminium crimp caps
- Details of trap for CO2: An aliquot (1.0 mL) of concentrated orthophosphoric acid was injected through the septum of each vessel taken for analysis in order to lower the pH of the medium to< 3. The vessels were then shaken at approximately 150 rpm for 1 hour at 20±1 °C prior to samples being withdrawn from the headspace and analysed for inorganic carbon.

SAMPLING
- Sampling frequency: Triplicate control, reference item and test item vessels sacrificed on days 0, 2, 6, 8, 10, 14, 16 and 21. On day 28, five replicate vessels were sacrificed for analysis. Triplicate toxicity control vessels were sacrificed on days 0, 8 and 14 for analysis.

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated culture medium
- Toxicity control: test item plus reference item in culture medium, to give a final concentration of 40 mg C/L, 9 replicate vessels.
Reference substance:
benzoic acid, sodium salt
Preliminary study:
The test item was a poorly water soluble, volatile, non-viscous liquid and hence for the purpose of the biodegradation test the test item was added directly to the test vessels using a high precision volumetric syringe.

Preliminary work conducted showed that a volume of 3.8 μI of test item injected into a test vessel using a gas tight micro-syringe gave a measured weight of 5.94 mg, mean of 15 separate weighings.
Test performance:
Variation in the degradation rates obtained on different sampling days was considered to be the result of normal biological variation between the respiration rates of replicate vessels. Due to the sacrificial nature of the study design, the degradation rates obtained on each sampling occasion were for individual replicate vessels and not the result of cumulative degradation values determined from a single vessel sampled on numerous occasions and as such variation in degradation rates on different sampling days was to be expected.
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
2 d
Parameter:
% degradation (CO2 evolution)
Value:
15
Sampling time:
6 d
Parameter:
% degradation (CO2 evolution)
Value:
18
Sampling time:
8 d
Parameter:
% degradation (CO2 evolution)
Value:
16
Sampling time:
10 d
Parameter:
% degradation (CO2 evolution)
Value:
23
Sampling time:
14 d
Parameter:
% degradation (CO2 evolution)
Value:
23
Sampling time:
16 d
Parameter:
% degradation (CO2 evolution)
Value:
22
Sampling time:
21 d
Parameter:
% degradation (CO2 evolution)
Value:
27
Sampling time:
28 d
Details on results:
The mean total inogranic carbon in the control vessels on Day 28 was 0.30 mg/I; equivalent to 14% of the organic carbon added initially as test item to the test vessels and therefore satisfied the validation criterion given in the Test Guideline.

The toxicity control attained 59% degradation after 14 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used in the study.
Results with reference substance:
Sodium benzoate attained 99% degradation after 14 days and 81% degradation 28 days thereby confirming the suitability of the inoculum and test conditions.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item attained 27% degradation after 28 days and therefore cannot be considered to be readily biodegradable.
Executive summary:

The assessment of ready biodegradability was performed according to the GLP-complaint study following OECD Guideline 310. This OECD guideline was selected as the preliminary work showed that the test item was volatile and the OECD Guideline 310 method is recommended for volatile materials.

 

The OFPMA (20 mg C/L) was exposed to non-adapted activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at 20 ± 1.0 °C for 28 days. The degradation was assessed by determination of carbon dioxide evolution on Days 0, 2, 6, 8, 14, 16, 21, and 28.

 

The toxicity control attained 59% degradation after 14 days thereby confirming that the test item was not toxic to the inoculum. The sodium benzoate attained 99% degradation at 14 days thereby confirming the suitability of the inoculum and test conditions. The test item attained 27% degradation after 28 days and therefore cannot be considered to be readily biodegradable.

Description of key information

The assessment of ready biodegradability was performed according to two GLP-complaint studies following OECD Guideline 310. The first study conducted in 2010 determined the OFPMA attained 27% degradation after 28 days and therefore cannot be considered to be readily biodegradable. The second study conducted in 2016 determined the OFPMA attained 22% degradation after 28 days and therefore cannot be considered to be readily biodegradable.

 

The 2016 study included compound analyses with GC/MS on Days 0, 14 and 28 from duplicate test item and inoculum control vessels. The test item (OFPMA) was shown to fairly quickly form the degradant, octafluoropentanol (CAS 355-80-6). It was considered that the test item that did not degrade to octafluoropentanol was suspected to have broken down to form methacrylic acid which was not analytically measured due to the amount formed being below the limit of quantification. The methacrylic acid was considered to have mineralized with carbon dioxide evolution shown by the inorganic carbon analyses. The concentration of the degradant on Day 14 (average of 29.6 mg/L) was similar to the concentration reported on Day 28 (average of 35.2 mg/L). Since the octafluoropentanol did not show evidence of mineralization within the 28-day study, the parent compound cannot be considered to be inherently biodegradable.

Key value for chemical safety assessment

Additional information