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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This study was in accordance with the EC Guideline and GLP. The test substance was equivalent to submission substance identity but the degree of purity was not available. Furthermore, no sufficient data was available to say that all validity criteria were fulfilled.
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
GLP compliance:
yes
Remarks:
The certificate copy was not included in the study report
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Inoculum comes from influent of Saint Germain au Mont d’Or STP; sampling date: 1998-02-04; no data was available about sampling method
- Laboratory culture: no data available
- Method of cultivation: no data available
- Storage conditions: no data available
- Storage length: 24 hours
- Preparation of inoculum for exposure: Sampling was filtered through glass fiber (elimination of big size particles) and the filtrate was centrifuged (no data was available about the centrifugation duration, speed and temperature). The centrifugation pellet was washed and recovered in a Ringer ¼ solution.
- Pretreatment: Inoculum was not pre-exposed to the test substance
- Concentration of sludge: no data available
- Initial cell/biomass concentration: 2.5*10E06 bacteria/mL (estimated by count in Petri dish). Inoculum was used at 1% in the test system
- Water filtered: yes
- Type and size of filter used, if any: The filter used was in glass fiber but no data was available about its size
Duration of test (contact time):
48 d
Initial conc.:
20 other: mg/kg
Based on:
other: TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: see table below
- Additional substrate: see below
- Solubilising agent (type and concentration if used): No solubilising agent was used.
- Test temperature: 21.4 to 22.2°C
- pH: no data available
- pH adjusted: no data available
- CEC (meq/100 g): no data available
- Aeration of dilution water: no data available
- Suspended solids concentration: no data available
- Continuous darkness: yes
TEST SYSTEM
- Culturing apparatus: Glassy Erlenmeyer flasks of 5 L
- Number of culture flasks/concentration: 3 culture flasks
- Method used to create aerobic conditions: no data available.
- Measuring equipment: no data available
- Test performed in closed vessels due to significant volatility of test substance: no data available
- Test performed in open system: no data available
- Details of trap for CO2 and volatile organics if used: Barita traps were used to trap CO2 (no detail was available)
SAMPLING
No data available
CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks (Inoculum in the mineral medium without the test substance)
- Abiotic sterile control: 1 flask (test substance in the mineral medium without the inoculum and with NaN3 10 g/L at 1% in the test solution)
- Adsorption control: no flask
- Toxicity control: 1 flask (test substance and reference substance with the inoculum in the mineral medium at 20 mg/kg for each one)
- other: Reference substance: 1 flask (reference substance with the inoculum in the mineral medium at 20 mg/kg)
STATISTICAL METHODS:
No data available
Reference substance:
acetic acid, sodium salt
Preliminary study:
No preliminary study was performed
Parameter:
% degradation (CO2 evolution)
Value:
30
Sampling time:
28 d
Remarks on result:
other: Result obtained by direct introduction of the substance
Parameter:
% degradation (CO2 evolution)
Value:
41
Sampling time:
48 d
Remarks on result:
other: Result obtained by direct introduction of the substance
Parameter:
% degradation (CO2 evolution)
Value:
48
Sampling time:
28 d
Remarks on result:
other: Results obtained by introduction of the substance after the store on sand.
Parameter:
% degradation (CO2 evolution)
Value:
54
Sampling time:
48 d
Remarks on result:
other: Results obtained by introduction of the substance after the store on sand.
Details on results:
The use of solid carrier (sand) gave better results than the direct introduction of the substance into the test medium.
No degradation was measured before 28 days in the abiotic control. Then 53.5 mg of CO2 were measured between 28 days and the end of test corresponding to 23% of degradation.
The test was prolonged until 48 days because the plateau has not been reached by day 28 (see table in section "overall remarks"). The biodegradation percentage of the test substance was below the pass level for ready biodegradability (i.e. 60%) at 28 days and at the end of the test.
Results with reference substance:
67% of degradation after 14 days
91% of degradation after 48 days
The degradation percentage of the reference substance was higher than 60% after 14 days.
The result obtained with the reference substance was valid.

Degradation percentages according to time:

Type of

suspension

Vessel

% degradation at sampling time (days)

0

1

4

7

14

21

28

35

42

48

Test sample

FE1

0

0

0

7

16

22

29

33

35

39

FE2

0

0

0

6

17

25

31

39

40

43

FE3

0

0

2

15

31

42

48

51

52

54

Reference

substance

FC

0

12

47

57

67

81

89

90

90

91

Inhibition

control

FI

0

7

26

35

44

52

58

61

63

65

Abiotic sterile

control

FA

0

0

1

1

0

0

0

3

12

23

Validity criteria:

-       The inorganic carbon content of the test chemical suspension in the mineral medium at the beginning of the test must be less than 5% of the total carbon content:

No data available

-       The total CO2 evolution in the inoculums blank at the end of the test should not normally exceed 40 mg/L medium:

YES, the CO2 quantities were respectively of 14 and 10.6 mg/L at 48 days.

-       The difference of extremes of replicate values of the removal test chemical at the plateau, at the end of the test or at the end of the 10 day window, as appropriate, is less than 20%:

YES, the difference of replicates values at the end of the test is less than 20%

-       The degradation percentage of the reference substance has reached the level for ready biodegradability for 14 days:

YES, the degradation percentage of the reference substance was 67% after 14 days.

Validity criteria fulfilled:
yes
Interpretation of results:
other: Not readily biodegradable
Conclusions:
On the basis of these results, it can be concluded that Rhodiastab 92 is not readily biodegradable.
Executive summary:

Rhodiastab 92 was tested for ready biodegradability according to the EU method C4-C (modified Sturm test), described in the Annex V of the Directive 67/548/EEC, and in compliance with the Good Laboratory Practice.

The biodegradation was calculated from the CO2 released measurements compared to the theoretical amount of CO2 for complete mineralization of the test substance. Due to its low water solubility, 2 test suspension flasks were prepared by direct addition of Rhodiastab X2, and a third test suspension flask was prepared using sand as solid carrier.

As a plateau was not reached in 28 days, the test was continued up to 48 days. The positive control was degraded to 67% within 14 days and no inhibition was detected with the toxicity control. All the validity criteria were fulfilled.

For the flasks prepared by direct addition of Rhodiastab X2, the percentages of biodegradation were 30% and 41%, within 28 days and 48 days respectively. The flask prepared with a solid carrier showed a higher level of biodegradation with values of 48% and 54%, within 28 days and 48 days respectively.

On the basis of these results, the Rhodiastab X2 is considered as not readily biodegradable.

Description of key information

A ready biodegradability test was performed according to the EU method C4-C (modified Sturm test), described in the Annex V of the Directive 67/548/EEC, and in compliance with the Good Laboratory Practice. The biodegradation was calculated from the CO2 released measurements compared to the theoretical amount of CO2 for complete mineralization of the test substance. Due to its low water solubility, 2 test suspension flasks were prepared by direct addition of Rhodiastab X2, and a third test suspension flask was prepared using sand as solid carrier.

As a plateau was not reached in 28 days, the test was continued up to 48 days. For the flasks prepared by direct addition of Rhodiastab X2, the percentages of biodegradation were 30% and 41%, within 28 days and 48 days respectively. The flask prepared with a solid carrier showed a higher level of biodegradation with values of 48% and 54%, within 28 days and 48 days respectively.

On the basis of these results, the Rhodiastab X2 is considered as not readily biodegradable.

The positive control was degraded to 67% within 14 days and no inhibition was detected with the toxicity control. All the validity criteria were fulfilled.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information