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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
Study period:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP/Guideline Study
Justification for type of information:
Please refer to analogue approach justification attached to section 13
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Activated sludge was collected from the Cambridge Wastewater Treatment Facility, Cambridge,
Maryland on 15 June 2012. The sludge was sieved using a 2 mm screen, adjusted to approximately
1000 mg total suspended solids/L with mineral media, then aerated at test temperature until its use in the
study. A total suspended solids (TSS) measurement and standard plate count were performed on the
inoculum the day the test chambers were prepared. Plates were incubated at 20 ± 1°C for approximately
48 hours.
Duration of test (contact time):
28 d
Initial conc.:
50 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The test medium was a modified biochemical oxygen demand (BOD) test dilution water and was
prepared using high quality water.
- Solubilising agent (type and concentration if used): acetone
- Test temperature: 20 ± 1°C.
- pH: 7.3
- pH adjusted: no
- Aeration of dilution water: yes

TEST SYSTEM
- Culturing apparatus: The test chambers were amber bottles with a nominal volume of 510 mL.
- Number of culture flasks/concentration: 2
- Measuring equipment: Achat OC Controller OC110

SAMPLING
- Sampling frequency:daily

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes

STATISTICAL METHODS:The results of the pressure measurements made by the Oxitop® respirometers were converted to
BOD (oxygen uptake) by the Achat OC Controller OC110. The results were converted to BOD for
the reference and test substances.
Reference substance:
aniline
Preliminary study:
none
Test performance:
The viability of the inoculum and validity of the test were supported by the results of the reference
substance. Based on the calculated theoretical oxygen demand of the reference substance aniline
(2.41 mg O2/mg), the average percent degradation after 28 days was 88.6%. An average
percent biodegradation of greater than 60% was achieved by day 14 and the average pH of the treatment
vessels was 7.3, falling within the range of 6-8.5 for the study, thereby fulfilling the criteria for a valid
test. Control, Solvent Control and Reference vessel average pH values were 7.6, 7.5 and
7.5 respectively.
Parameter:
% degradation (O2 consumption)
Value:
-1.6
Sampling time:
28 d
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Evidence of ready biodegradability in a Manometric Respirometry Test is 60% ThOD within the
28-day test period. In addition, the 60% pass level must be reached within 10 days of achieving 10%
ThOD. The test substance, XU-18838.00, is not considered readily biodegradable under the
conditions of this study since the pass level was not achieved. The average percent degradation at the
end of the 28th day was –1.6%.
Executive summary:

The ready biodegradability of XU-18838.00 was determined by the manometric respirometry test method (OECD Guideline 301F). Tests of ready biodegradability are stringent tests that provide limited opportunity for acclimation and biodegradation to occur. In the manometric respirometry test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and stirred in a closed bottle at constant temperature for 28 days. The consumption of oxygen was determined by measuring the change in pressure in the apparatus. The amount of O2 taken up by the microbial population during biodegradation of the test substance (corrected for uptake by the blank inoculum) was expressed as a percentage of ThOD. The test contained a blank control group, a solvent control group, a reference group and a treatment group. Each group contained two replicate test chambers. The blank control was used to measure the background O2 uptake of the inoculum and was not dosed with a carbon source. The solvent control was used to monitor any effect of the test substance dosing solution solvent on the test system and was treated with the same solvent used as a carrier for the test substance. The reference chambers were dosed with aniline, a substance known to be biodegradable, at a nominal concentration of 50 mg/L. The treatment group test chambers were used to evaluate the test substance at a nominal concentration of 50 mg/L. The results indicated that the activated sludge inoculum was active, degrading the reference substance an average of 88.6%. The test substance, XU-18838.00, is not considered readily biodegradable under the conditions of this study since the pass level was not achieved. The average percent degradation at the end of the 28th day was –1.6%.

Description of key information

A Manometric Respirometry test (OECD 301F) was performed on((3,4-bis(Hexyloxy)phenyl)methanetriyl) tribenzene, which has a closely related structure to the registered substance. Based on the observation of -1.6% biodegradation over the course of the 28-day exposure, the conclusion for((3,4-bis(Hexyloxy)phenyl)methanetriyl) tribenzeneis that the test material was not readily biodegradable. Employing a read across argument, the registered substance is also considered not readily biodegradable.

Justification for the use of read-across is provided in the document attached to section 13 of the dossier.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information