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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:
1999-03-10 to 1999-04-12
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Remarks:
Test substance ID is incomplete as cis/trans isomers ratio is unspecified.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Remarks:
Statement of compliance with GLP in date of 1999-04-27
Specific details on test material used for the study:
No additional information
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day,
Concentration of sludge: 3.386 g/L (dry weight of suspended solids); to obtain a concentration of 30 mg/L (dry weight) in a 250 mL flask, 2.22 mL of sludge is needed (inoculum).
Duration of test (contact time):
32 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium; compliant with recommendations of TG on mineral medium; the pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Solubilising agent (type and concentration if used): None
- Test temperature: 22 °C
- CEC (meq/100 g): No data
- Aeration of dilution water: No data
- Suspended solids concentration: 30 mg/L
- Continuous darkness: No data
- Water: The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

TEST SYSTEM
- Culturing apparatus: Test flasks of the SAPROMAT
- Number of culture flasks/concentration: 2
- Measuring equipment: The respirometer used during this study is a SAPROMAT D 12, made by J. M. VOITH GmbH, D-7920 Heidenheim.
- Test performed in closed vessels: Yes
- Test performed in open system: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes, inoculum only
- Procedure control: Yes, with the reference substance
- Toxicity control: Yes, test item and reference substance

OTHER:
Toxicity of the test chemical
As suggested in the OECD 301 F method, the toxicity of the test chemical for the inoculum is checked Therefore, a pair of flasks of the volumetric respirometer (SAPROMAT) are filled with mineral medium + test chemical (100 mg/L) + reference substance (100 mg/L) + inoculum and their respirations are recorded as for the other flasks. If they are lower than those of the flasks containing mineral medium + reference substance (100 mg/L) + inoculum, the test chemical can be assumed to be inhibitory to the inoculum used.
Reference substance:
benzoic acid, sodium salt
Remarks:
100 mg/L
Preliminary study:
None
Test performance:
Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked. At the end of the test period (normally 28 days), the pH of each flask is measured again
Key result
Parameter:
% degradation (O2 consumption)
Value:
88
Sampling time:
28 d
Remarks on result:
other: >60% within the 10d window
Parameter:
% degradation (O2 consumption)
Value:
88
Sampling time:
32 d
Details on results:
Test substance undergoes 88% biodegradation after 32 days (also 88% after 28 days) in the test conditions. Biodegradation starts on day 2 and reaches 82% at the end of the 10-day window (days 2 to 12).
The curves obtained with the reference substance alone and with test substance + reference substance show no toxic effect of test substance to the micro-organisms at the test concentration. Test substance at 100 mg/L is not inhibitory to the micro-organisms.
Results with reference substance:
Degradation of sodium benzoate exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified and the test is considered as valid.

Table 5.2.1/2: Test substance - Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations)

 

Days:

2

5

12

21

28

32

BOD sludge

1st flask

B1

4.0

10.0

14.0

18.0

22.0

22.0

2nd flask

B2

0.0

6.0

8.0

10.0

14.0

14.0

mean

B

2.0

8.0

11.0

14.0

18.0

18.0

BOD test substance

1st flask

C1

34.8

152.8

189.6

201.3

208.2

209.2

2nd flask

C2

31.3

149.6

187.8

201.5

209.4

209.4

1st flask corr.

C1-B

32.8

144.8

178.6

187.3

190.2

191.2

2nd flask corr.

C2-B

29.3

141.6

176.8

187.5

191.4

191.4

% biodegradation

 

1st flask

D1

15

67

82

86

88

88

2nd flask

D2

14

65

81

86

88

88

mean

D

14

66

82

86

88

88

 

Calculations:

B = (B1 + B2) / 2

D1 = 100 * (C1 - B) / ThOD * [S]

D2 = 100 * (C2 - B) / ThOD * [S]

D = (DI + D2)/2

[S] : Initial test substance concentration (mg/L)

ThOD: 2.17 mg O2/mg

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Test substance undergoes 88% biodegradation after 28 and 32 days in the test conditions. Biodegradation starts on day 2 and reaches 82% at the end of the 10-day window (days 2 to 12). Thus, test substance should be regarded as readily biodegradable according to this test. In addition, no toxic effects of the test substance were observed to microorganisms at the test concentration.
Executive summary:

The ready biodegradability of the test item has been determined by the Manometric Respirometry Test according to the OECD Guideline No. 301F with GLP compliance.

A nominal concentration of test substance (100 mg/L) introduce in the system.

 

Test substance undergoes 88% biodegradation after 28 and 32 days in the test conditions. Biodegradation starts on day 2 and reaches 82% at the end of the 10-day window (days 2 to 12). Test substance at 100 mg/L is not inhibitory to the micro-organisms. Degradation of sodium benzoate exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified and the test is considered as valid. 

According to this test, the conclusion is that the test item should be regarded as readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
[further information is included as attachment to Iuclid section 13]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the structural similarity between the source and the target substances. Their environmental properties are expected to be similar because of this structural similarity and because they are anticipated to follow the same environmental fate.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target and the source substances are structurally related, in that each has a 2-methyl ether benzene ring, and a propen-2-yl group in 4- position. The source substance is the mixture of the target (i.e. trans-isomer) and cis-isomer. No impurities were reported above 1% of lower if contributing to the hazard of PBT profile. Therefore, it's expected that the impurities will not affect the read-across.

3. ANALOGUE APPROACH JUSTIFICATION
The source substance is not unequivocally identified in the available study (cis and/or trans isomers, cause for restrictions). However, based on structural similarity, no difference on the biodegradability potential is anticipated between trans and cis isomers. Hence, it is considered suitable and scientifically justified to read-across the data between the two substances to fill the biodegradation endpoint in the present dossier.

4. DATA MATRIX
See attached document in Iuclid section 13
Reason / purpose:
read-across source
Reason / purpose:
read-across: supporting information
Key result
Parameter:
% degradation (O2 consumption)
Value:
88
Sampling time:
28 d
Remarks on result:
other: >60% within 10d window
Parameter:
% degradation (O2 consumption)
Value:
88
Sampling time:
32 d
Details on results:
Biodegradation starts on day 2 and reaches 82% at the end of the 10-day window (days 2 to 12).
The curves obtained with the reference substance alone and with test substance + reference substance show no toxic effect of test substance to the micro-organisms at the test concentration. Test substance at 100 mg/L is not inhibitory to the micro-organisms.
Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Conclusions:
Based on data available on the source substance (88% biodegradation after 28d within the 10d window), the target and the source substances are readily biodegradable and non-toxic to microorganisms up to 100 mg/L.
Executive summary:

The ready biodegradability of the target substance has been determined by the Manometric Respirometry Test, performed on the source substance according to the OECD Guideline No. 301F with GLP compliance.

A nominal concentration of test substance (100 mg/L) was introduce in the system. Test substance undergoes 88% biodegradation after 28 and 32 days in the test conditions. Biodegradation starts on day 2 and reaches 82% at the end of the 10-day window (days 2 to 12). Test substance at 100 mg/L is not inhibitory to the micro-organisms. Degradation of sodium benzoate exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified and the test is considered as valid. According to this test, the conclusion is that the source and the target substance should be regarded as readily biodegradable.

Description of key information

Read-across, OECD Guideline 301F, GLP, key study, validity 2:

88% biodegradation after 28 days within the 10-day window. Readily biodegradable. Non-toxic to microorganisms up to 100 mg/L.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One valid key study is available (Givaudan, 1999), to assess the readily biodegradation of the registered substance, (E)-2 -Methoxy-4 -prop-1 -en-1 -ylphenyl acetate.

This study was performed on a source substance (ratio of cis/trans isomers), according to OECD Guideline 301F and GLP. Based on chemical similarity, no significant difference on the biodegradability potential is anticipated with the present dossier substance (trans isomer), so the read-across is considered justified for a key study. The test substance at 100 mg/L was inoculated with activated sludge from a biological wastewater treatment plant treating predomenantly domestic sewage. The degradation of the test substance was assessed by the determination of the oxygen consumption. The test substance undergoes 88% biodegradation after 28 and 32 days in the test conditions. Biodegradation starts on day 2 and reaches 82% at the end of the 10 day window (days 2 to 12). Therefore, the test substance is considered readily biodegradable. In the toxicity control, containing both the test substance and the reference substance (sodium benzoate), the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L. In the procedure controls, the degradation of the reference substance exceeds 40% after 7 days and 65% after 14 days, thus confirming suitability of the activated sludge.

In conclusion, according to this study, the registered substance can be considered readily biodegradable and non-toxic to microorganisms up to 100 mg/L.