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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:
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

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source and target substances have similar toxicological properties because
- they are manufactured from similar precursors under similar conditions
- they share structural similarities with common functional groups: the substances start with an acetylene group as core structure; geminal hydroxyl groups on the alpha carbon atoms; distal to the geminal hydroxyl groups is an isobutyl group (methyl isopropyl); the target substance 2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (1.3) is further functionalised with ethylene oxide and has an ethoxylation degree of 1.3; the source substance 2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (3.8) has an ethoxylation degree of 3.8
- they have similar physicochemical properties and thus, show a similar toxicokinetic behaviour
- they are expected to undergo similar metabolism: oxidation of the terminal methyl groups to result in alcohol, aldehyde and finally the corresponding acid

Therefore, read-across from the existing toxicity, ecotoxicity, environmental fate and physicochemical studies on the source substances is considered as an appropriate adaptation to the standard information requirements of REACH regulation.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
see “Justification for read-across” attached to IUCLID section 13

3. ANALOGUE APPROACH JUSTIFICATION
see “Justification for read-across” attached to IUCLID section 13

4. DATA MATRIX
see “Justification for read-across” attached to IUCLID section 13
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across: supporting information
Oxygen conditions:
aerobic
Duration of test (contact time):
28 d
Parameter:
% degradation (DOC removal)
Remarks:
ready biodegradation tests
Value:
< 10
Sampling time:
28 d
Parameter:
% degradation (TOC removal)
Remarks:
inherent biodegradation test
Value:
25.4
Sampling time:
57 d
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (1.3) is not readily biodegradable.

Description of key information

not readily biodegradable (read-across from  2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (3.8) and 2,4,7,9-Tetramethyl-5-decyne-4,7-diol)

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

Experimental data on the biodegradation of 2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (1.3) are not available. However, several studies were conducted with the structurally related source substances2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (3.8)and 2,4,7,9-Tetramethyl-5-decyne-4,7-diol. A justification for read-across is attached to iuclid section 13.

 

Ready biodegradation tests

2,4,7,9-Tetramethyl-5-Decyne-4,7-Diol was tested for its ready biodegradability in the carbon dioxide (CO,) evolution test (modified Stunn test) at 36.3 p1 per 2 litres, corresponding with 12 mg TOC/l. The Theoretical CO, production (ThCO,) of 2,4,7,9-Tetramethyl-5-Decyne-4,7-Diwoals calculated to be 2.72 mg CO2/mg, corresponding with 2.42 mg CO,/pl. The relative degradation values calculated from the measurements performed during the test period revealed no significant degradation of 2,4,7,9-Tetramethyl-5-Decyne-4,7-DioInl. t he toxicity control of 2,4,7,9- Tetramethyl-5-Decyne-4,7-Diol was found to be not inhibitory.

2,4,7,9-TETRAMETHYL-5-DECYNE-4,7-DIOL was not readily biodegradable under the conditions of the modified Sturm test presently performed.

 

The test substance 2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (3.8) was degraded by 1% after 28 days. Based on this, the test substance, cannot be characterised as readily biodegradable in the marine environment according to the OECD guideline (1992).

 

Tests for inherent biodegradation

In the 'Zahn-Wellens I EMPA Test' presently performed, no significant degradation of 2,4,7,9-Tetramethyl-5-decyne-4,7-diol was observed within the study duration of 28 days.

Thus, the substance was not inherently biodegradable under the conditions of the 'Zahn-Wellens I EMPA Test' presently performed.

 

2,4,7,9-Tetramethyl-5-decyne-4,7-diol was tested in a Semi-continuous Activated Sludge System (SCAS) at a daily dosage level starting at approximately 8-10 ppm as TOC, but later continued at an average dosage level of 15 ppm. Test data showed that the test substance is "inherently biodegradable": that it reached a level of greater than 20% degradation, as defined by OECD Test Method 302A.

 

In an Ultimate Aerobic Biodegradability according to ISO DIS 9439 2,4,7,9-Tetramethyldec-5-yne-4,7-diol was poorly biodegradable and poorly eliminable from water as well in this CO2/DOC combination test based on the quantitative determination of the formed carbon dioxide in comparison to the calculated maximal theoretical carbon dioxide production and on the determination of the removal of DOC in comparison to the calculated DOC concentration at start of exposure respectively.

The required pass levels for the inherent biodegradability and a well elimination were not reached.

After an exposure period of 60 days the degree of biodegradation was <10 % expressed as % CO2/ThCO2. The degree of elimination was <10 % as well, expressed as removal of DOC.

The degrees of biodegradation and elimination were calculated as means of the values from two test assays at the end of exposure.

Based on determined rate of biodegradation and rate of DOC removal at the end of exposure the test substance can be evaluated as poorly biodegradable and poorly eliminable from water.

 

 

Overall, die target substance 2,4,7,9-Tetramethyl-5-decyne-4,7-diol, ethoxylated (1.3) is considered to be not readily biodegradable.