Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
09 July 2013 to 27 March 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Fully GLP compliant and in accordance with current test guidelines

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report Date:
2014

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
Name: Oxypyrionacetate
CAS number: 1742-79-6
Batch number: 14058400
Molecular weight: 153 g/mol
Storage details: stored refrigerated (2 °C to 8 °C) in the dark
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Reference substance: diethylene glycol
Carbon content: expressed as a percentage by weight is 45.27%.

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
A sample of activated sludge was collected from one of the return lines at Burley Menston sewage treatment works (West Yorkshire, UK), which has a predominantly domestic waste-water catchment. The sample was transported to Smithers Viscient in a closed container, but with an adequate headspace, to prevent the sample becoming anaerobic.
On arrival, the sample was washed by allowing the solids to settle, removing the supernatant and replacing it with an equal volume of mineral media. The washed sample was aerated by means of a compressed air supply.
The suspended solids concentration of the activated sludge was determined by filtering a subsample (25 mL) through a pre-dried and pre-weighed glass microfibre filter (Whatman GF/C). The filter and retained solids were then dried in an oven and re-weighed. The weight of the sludge solids was determined from the difference in the weights before and after drying.
The activated sludge used in this study was not deliberately acclimatised or adapted to oxypyrion acetate before exposure under test conditions.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
50 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
-Composition of medium: The mineral medium used in this study (after dilution of the mineral medium concentrate) contained 10 mL/L solution of Potassium dihydrogen phosphate (8.50 g), Dipotassium hydrogen phosphate (21.75 g), Disodium hydrogen phosphate dihydrate (33.40 g) and Ammonium chloride (0.50 g), 1 mL/L of each of Calcium chloride dihydrate (36.40 g), Magnesium sulphate heptahydrate (22.50 g), Ferric chloride hexahydrate (0.25 g) and Hydrochloric acid (1 drop).
- Test temperature: 22 ± 2°C
- pH: 7.48 to 7.51 at Day 0 and 7.40 to 7.55 at Day 28
- pH adjusted: no
- CEC (meq/100 g): Not applicable
- Aeration of dilution water: was delivered from a cylinder of CO2-free air (Air Products)
- Suspended solids concentration: Not reported
- Continuous darkness: yes

TEST SYSTEM
- Method used to create aerobic conditions: aerated by means of a compressed air supply
- Details of trap for CO2 and volatile organics if used: . Each vessel was sealed, connected to a series of three traps containing aqueous barium hydroxide (nominally 0.0125M)

SAMPLING
- Sampling frequency: 2, 5, 7, 9, 12, 14, 19, 23, 28 and 29 Day
- Sampling method: trap bottle nearest to the test vessel was removed for sampling. The initial barium hydroxide stock concentration and the residual concentrations in detached trap bottles were determined by titration against hydrochloric acid (nominally 0.05M) using 0.5% ethanolic phenolphthalein indicator solution.
- Sterility check if applicable: Not applicable
- Sample storage before analysis: Not applicable

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated mineral salts medium
- Abiotic sterile control: Mineral salts medium inoculated with sterilised inoculum and test substance
- Toxicity control: inoculated mineral salts medium, test substance and diethylene glycol
- Other: Dose control - Un-inoculated mineral salts medium and test substance
Reference substance
Reference substance:
diethylene glycol

Results and discussion

Preliminary study:
Not applicable
Test performance:
pH values in all vessels ranged from 6,52 to 8,08. DO measurements in all vessels ranged from 6,89 mg/l to 8,68 mg/l indicating aerobic conditions. The pH and DO values were within the limits specified in the protocol with one deviation: at Day 21 the abiotic control pH (8.08) was slightly higher than the limit of 8.0 and was not adjusted in error. The pH of the abiotic control vessel was within the limits at the following two sampling occasions. This is not considered to have had an impact on the integrity of the study.
% Degradation
Key result
Parameter:
% degradation (CO2 evolution)
Value:
99
Sampling time:
29 d
Remarks on result:
other: inherently biodegradable
Remarks:
Not readily biiodegradable
Details on results:
To be considered inherently biodegradable, a test substance must achieve 20% biodegradation by the end of the test. After 2 days, 22% mean biodegradation was observed; by the end of the test, 99% mean biodegradation was observed and oxypyrion acetate can therefore be considered to be inherently biodegradable.
Assessment of biodegradation in the toxicity control was calculated for the diethylene glycol fraction only. The biodegradation of the reference substance in the presence of oxypyrion acetate was 100% at 14 days, suggesting that oxypyrion acetate did not have an inhibitory effect on the sludge microorganisms under the test conditions. Results from study 3200294 show that oxypyrion acetate degrades rapidly in water to oxypyrion and (theoretically) acetic acid.

BOD5 / COD results

Results with reference substance:
The mean percentage biodegradation for vessels containing the reference substance alone was 100% at Day 14. The validity criterion of 70% removal at 14 days was therefore met.

Any other information on results incl. tables

Biodegradation as a Percentage of Initial Carbon Concentration

 

% Biodegradation

Day 2

Day 7

Day 14

Day 21

Day 27

Day 28

Reference substance replicate 1

1

100

100

100

100

100

Reference substance replicate 2

5

100

100

100

100

100

Mean

3

100

100

100

100

100

Test substance replicate 1

21

78

100

100

100

100

Test substance replicate 2

23

88

100

100

100

99

Mean

22

83

100

100

100

99

Toxicity control

17

24

100

101

100

101

Abiotic control

1

38

96

98

97

97

Note: Numbers are rounded for presentation. Consequently, the displayed mean may not be the calculated mean of the rounded individual values shown.

All values are corrected for blank control.

Negative numbers are reported as zero.

Toxicity Control results are expressed in terms of concentration of reference substance alone.

 

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The validity criterion was satisfied and the results of this study are therefore considered to be valid.
Biodegradation of oxypyrion acetate was 22% after 2 days and 99% at 28 days. The level of biodegradation observed satisfies the requirements for inherent biodegradability and oxypyrion acetate can therefore be classified as inherently biodegradable.
Executive summary:

The inherent and primary biodegradability of oxypyrion acetate was assessed by measurement of dissolved organic carbon elimination under standard conditions. The study was carried out in accordance with OECD Guideline 302B, Zahn Wellens/EMPA test (Adopted July 1992).

The test substance, oxypyrion acetate (CAS 1742-79-6), was added to the test system in an aqueous solution to give a test substance concentration equivalent to 50 mg organic carbon/l. The procedure and the activity of the inoculum were checked by measuring the dissolved organic carbon (DOC) eliminated from vessels containing a reference substance, diethylene glycol. Blank control, abiotic control and toxicity control groups were also included.

The medium was inoculated with microorganisms derived from a sample of activated sludge not previously intentionally exposed to the test substance. Test vessels were incubated in darkness at 20 – 24 °C for 28 days and their contents continuously stirred and aerated. At intervals, samples were removed and subjected to DOC analysis (and HPLC-MS analysis, where appropriate).

Mean % biodegradation of oxypyrion acetate was 22% after 2 days, reaching 99% at 28 days. The level of biodegradation observed satisfies the requirements for inherent biodegradability and oxypyrion acetate can therefore be classified as inherently biodegradable. Results from study 3200294 show oxypyrion acetate degrades rapidly in water to oxypyrion and (theoretically) acetic acid.

All validity criteria were satisfied and the results of this study are therefore considered to be valid.