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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:
Start date: 23 Dec 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions (no GLP, no purity data)
Justification for type of information:
See the document "Rationale & justification for the Analogue read across approach used in the registration dossier of 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate CAS 59219-71-5" in section 13.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
adopted 1992
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum: Activated sludge was obtained on 22 Dec 2010 from the sewage treatment plant at Maxéville, France, which treats predominantly domestic sewage (98%).
- Treatment of sludge: On the day of collection, the sludge was washed three times with culture medium (centrifugation for 10 min at 1100 x g followed by resuspension) and sieved through a sieve (100 µm mesh size).

Duration of test (contact time):
28 d
Initial conc.:
19.7 mg/L
Based on:
test mat.
Initial conc.:
15 mg/L
Based on:
other: TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: as stated in the guideline 301 A
- Test temperature: 22 ± 2 °C
- Suspended solids concentration: ≤ 30 mg/L

TEST SYSTEM
- Culturing apparatus: 1 L test flasks containing 1 L test culture
- Number of culture flasks/concentration: 3
- Measuring equipment: indirect measurement of produced carbon dioxide using an automatic respirometer

SAMPLING
- Sampling frequency: continuous measurement (respirometer)

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 5 replicates
- Toxicity control: not included; respiration inhibition test (OECD 209) with NOEC (3 h) ≥ 1000 mg/L is referenced.
- Positive control: acetic acid, sodium salt: 3 replicates
- Abiotic sterile control: no
Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
91
Sampling time:
28 d
Details on results:
- The 10-day-window was defined from day 4 to day 14. As the test item attained 13% degradation on day 4 and 61% on day 14, this criterion is fulfilled.
Results with reference substance:
The reference substance attained 93% degradation after 14 days, 60% pass level was reached.

Table 1: Degradation kinetics of the test item and controls during 28 days of contact time. The 10-day-window was defined from day 4 to day 14.

Days

Degradation (%) after 28 days

Test item

Positive control

1

4

17

2

4

49

3

6

60

4

13

70

5

18

75

6

26

79

7

32

83

8

38

86

9

42

87

10

46

89

14

61

93

15

63

93

20

78

94

25

85

96

28

91

97

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The substance branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3) is readily biodegradable with 91% biodegradation in 28 days.
Executive summary:

The biodegradation of the source substance branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3) was conducted according to the OECD Guideline 301B (non-GLP) under aerobic conditions using activated sludge from a sewage treatment plant treating predominantly domestic sewage as inoculum. A mean biodegradation of 91% was observed after 28 d. Since the substance reached the pass level for OECD 301B (biodegradation is > 60% after 28 d, 10-day window fulfilled) branched-nonyl 3,5,5 trimethylhexanoate is readily biodegradable according to the OECD criteria.

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:
See the document "Rationale & justification for the Analogue read across approach used in the registration dossier of 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate CAS 59219-71-5" in section 13.
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (CO2 evolution)
Value:
91
Sampling time:
28 d
Remarks on result:
other: Readily biodegradable
Remarks:
10day-windows fulfilled
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradation of 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate is 91% in OECD 301B test. This substance is considered as readily biodegradable.
Executive summary:

Since no studies investigating the biodegradation of 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate (CAS 59219-71-5) are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally related analogue substance, branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3) was conducted. This read across is justified, as both source and target substances are characterized by equal fatty acid moieties ( 3,5,5 trimethylhexanoic acid) and/or similar alcohol moieties (C9 iso alcohol with varying branching options). The read-across is justified in more detail within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.

The target substance 3,5,5 -trimethylhexyl 3,5,5 -trimethylhexanoate (CAS 59219 -71 -5) was considered as readily biodegradable with a percentage of biodegradation reaching 91% in 28 days (10 day-windows fulfilled) in the OECD 301B test.

Description of key information

Readily biodegradable: 91% (CO2 evolution) after 28 d (OECD 301B), read across

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no studies investigating the ready biodegradability of 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate (CAS 59219-71-5) are available for this endpoint, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally related analogue substance branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3) was conducted. This read across is justified, as both source and target substances are characterized by equal fatty acid moieties ( 3,5,5 trimethylhexanoic acid) and/or similar alcohol moieties (C9 iso alcohol with varying branching options). The read-across is justified in more detail in the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.

The key study with the source substance branched-nonyl 3,5,5 trimethylhexanoate was conducted according to the OECD Guideline 301B (non-GLP) under aerobic conditions using activated sludge from a sewage treatment plant treating predominantly domestic sewage as inoculum. A mean biodegradation of 91% was observed after 28 d. Since the substance reached the pass level for OECD 301B (biodegradation is > 60% after 28 d, 10-day window fulfilled) branched-nonyl 3,5,5 trimethylhexanoate is readily biodegradable according to the OECD criteria. A second study was not used for the assessment since the validity criteria were not fulfilled (Barthel, 2010). In this study, according to OECD 301B, the biodegradation values from the six replicates differed by more than 20%. Therefore, the result is not reliable (65% biodegradation after 28d), but support the biodegradation result of the key study. In conclusion, the substance can be considered as readily biodegradable according to the OECD criteria.

Based on the results from the structurally related source substance, branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3), it can be concluded that 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate (CAS 59219-71-5) is readily biodegradable according to the OECD criteria.