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Environmental fate & pathways

Biodegradation in soil

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Administrative data

Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
key study
Study period:
June - October 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guidline/GLP-compliant study performed by an experienced laboratory

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: OECD 302 D, Proposed, Inherent Biodegradability
Principles of method if other than guideline:
Pre-exposed soil/activated sludge were addied to mineral test media and incubated under aerobic conditions for 90 d. Hexadecane served as the positive control. Replicate chambers were analyzed at intervals during the test for inorganic carbon and 14C-parent and metabolites. Conditions were optimized in favor of biodegradation.
GLP compliance:
yes
Test type:
laboratory

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Details on test material:
The test substance was received from Albemarle Corporation on November 28, 2007 and was
assigned Wildlife International, Ltd. identification number 8303. The following is a description of
the test substance used in this study:
Identity: Saytex® 8010
Lot Number: S17009C
Physical Description: Solid
Purity: 97.6%
Expiration Date: November 26, 2012
Storage Conditions: Room temperature in a closed container
Carbon Content: 17.30%
The test substance was administered to the treatment group test chambers by direct weight
addition. Direct weight addition is an appropriate route of administration for poorly water-soluble
materials. The amount of test substance used to dose the treatment group test chambers, was
calculated based on the carbon content. The carbon content of the test substance was determined
based on the molecular weight and chemical formula of the test substance.
The radiolabeled form of the test substance was received from Perkin Elmer on February 23,
2010 and was assigned Wildlife International, Ltd. identification number 9412. The following is a
description of the radiolabeled test substance used in this study:
Name: 1,2-Bis[pentabromophenyl]ethane, [Phenyl-14C[U]]
Lot number: 3626190
Formula weight: 972
Specific activity: 32.4 mCi/mmol, (33.3 μCi/mg)
Radiochemical purity: 94.5%
Sample form: solid
Specific details on test material used for the study:
The test substance was received from Albemarle Corporation on November 28, 2007 and was
assigned Wildlife International, Ltd. identification number 8303. The following is a description of
the test substance used in this study:
Identity: Saytex® 8010
Lot Number: S17009C
Physical Description: Solid
Purity: 97.6%
Expiration Date: November 26, 2012
Storage Conditions: Room temperature in a closed container
Carbon Content: 17.30%
The test substance was administered to the treatment group test chambers by direct weight
addition. Direct weight addition is an appropriate route of administration for poorly water-soluble
materials. The amount of test substance used to dose the treatment group test chambers, was
calculated based on the carbon content. The carbon content of the test substance was determined
based on the molecular weight and chemical formula of the test substance.
The radiolabeled form of the test substance was received from Perkin Elmer on February 23,
2010 and was assigned Wildlife International, Ltd. identification number 9412. The following is a
description of the radiolabeled test substance used in this study:
Name: 1,2-Bis[pentabromophenyl]ethane, [Phenyl-14C[U]]
Lot number: 3626190
Formula weight: 972
Specific activity: 32.4 mCi/mmol, (33.3 μCi/mg)
Radiochemical purity: 94.5%
Sample form: solid
Radiolabelling:
yes

Study design

Oxygen conditions:
aerobic
Soil classification:
not specified
Year:
2010
Details on soil characteristics:
Soil was collected from Claiborne, MD and used the same day of collection. Activated sludge was collected from the Cambridge Wastewater Treatment Facility, Cambridge, MD, which treats predominantly residential wastes. The sludge was seved using a 2-mm screan and aerated until use.
Duration of test (contact time)open allclose all
Soil No.:
#1
Duration:
> 0 - < 90 d
Soil No.:
#2
Duration:
> 0 - < 90 d
Initial test substance concentrationopen allclose all
Soil No.:
#1
Initial conc.:
20 other: mg C/L
Soil No.:
#2
Initial conc.:
70 other: ug/L
Parameter followed for biodegradation estimation:
radiochem. meas.
Experimental conditions
Soil No.:
#1
Temp.:
19.5 - 22.3 degrees C
Details on experimental conditions:
The aerobic inocula were pre-exposed to DBDP-Ethane prior to use. For each group, soil (1.0 g), activated sludge (2 ml) and yeast extract (50 mg) were added to test medium (1 L). The pH was adjusted to 7.4 ± 0.2, and DBDP-Ethane added at concentrations equivalent to 4, 8, and 8 mg C/L on days 0, 7 and 11, respectively. The contents were mixed with a magnetic stirrer and allowed gaseous exchange with a foam stopper for the duration of the pre-exposure. On day 14, the inoculum was screened (filter paper) and aerated overnight to reduce the organic carbon content. On the day of use, the inoculum was sparged with CO2-free air for 1 hour, and the dissolved organic (DOC) and inorganic (DIC) levels measured.

Results and discussion

% Degradationopen allclose all
Key result
Soil No.:
#1
% Degr.:
0
Parameter:
inorg. C analysis
Sampling time:
90 d
Remarks on result:
not determinable
Key result
Soil No.:
#2
% Degr.:
0
Parameter:
radiochem. meas.
Sampling time:
90 d
Remarks on result:
not determinable
Half-life / dissipation time of parent compoundopen allclose all
Key result
Soil No.:
#1
DT50:
> 90 d
Temp.:
20 °C
Remarks on result:
other: not calculated
Key result
Soil No.:
#2
DT50:
> 90 d
Temp.:
20 °C
Remarks on result:
other: not calculated
Transformation products:
no
Details on transformation products:
There were no transformation products.
Evaporation of parent compound:
no
Volatile metabolites:
no
Details on results:
Table 1. Inherent aerobic biodegradation results of decabromodiphenyl ethane (DBDP-Ethane) and hexadecane as the test and reference substances, respectively, expressed as inorganic carbon (IC) and percent of theoretical inorganic carbon (TIC) evolved (Mean ± Standard deviation; n=3 chambers/group D 14-73; n = 5 chambers/group D90).

Day IC (mg C/L) % TIC Evolved
Blank Hexadecane DBDP-Ethane Blank Hexadecane DBDP-Ethane
14 1.0 ± 0.1 16.3 ± 0.9 1.2 ± 0.1 NA 76.5 ± 4.4 1.2 ± 0.4
28 1.2 ± 0.4 19.2 ± 1.9 0.9 ± 0.1 NA 90.2 ± 9.6 -1.6 ± 0.5
42 1.6 ± 0.4 22.9 ± 1.9 2.4 ± 0.6 NA 106.3 ± 9.8 4.3 ± 3.1
56 1.9 ± 0.3 23.1 ± 2.0 2.3 ± 0.4 NA 106.1 ± 10.1 2.3 ± 1.9
73 2.6 ± 0.2 23.1 ± 1.8 3.2 ± 0.3 NA 103.1 ± 9.2 3.1 ± 1.4
90 2.9 ± 1.2 23.0 ± 1.9 3.4 ± 0.9 NA 100.1 ± 9.3 2.2 ± 4.5
Overall Mean* 1.9 ± 0.8 21.3 ± 2.9 2.2 ± 1.0 NA 97.0 ± 11.7 1.9 ± 2.0
NA=not applicable.
*Calculated from means.

Results with reference substance:
see results

Any other information on results incl. tables

The test met the validity criteria specified in the guideline. The mean percentage biodegradation of hexadecane was ≥60% ThIC and was reached by Day 14, indicating the inoculum was viable and performed as expected. Further, the mean amount of IC produced by the blank controls at the end of the test was ≤15% of the organic carbon added initially as DBDP-Ethane to the test bottles.  

The mean evolved IC from the hexadecane reference group was substantially greater than either the untreated control or the DBDP-Ethane treatment group on all days while the mean evolved IC in the DBDP-Ethane group was similar to that of the untreated control (Table 1). While bottles treated with hexadecane evolved a mean of 97.0 % ThIC over the study, ThIC evolved from the DBDP-Ethane bottles was similar to the blank controls. Substances are considered to lack inherent biodegradation when <= 20% ThIC is evolved.  

The entire contents of the test chamber were extracted and analyzed for14C-activity. No indication of degradation of [14C]DBDP-Ethane was observed on HPLC/β-RAM analysis. One peak containing the radiolabel was detected. That peak had a retention time consistent with the parent molecule.

Applicant's summary and conclusion

Conclusions:
Not inherently biodegradable under optimized conditions over a 90 d period.
Executive summary:

Inherent biodegradation of DBDP-Ethane by a mixture of pre-exposed sludge and soil bacteria over a 90-day period was not observed. Two methods were used to investigate biodegradation: ThIC and14C-analysis for the parent molecule and metabolites. Because inherent biodegradation tests are designed to assess whether a chemical has any potential for biodegradaton (OECD, 2006), the observed results suggest DBDP-Ethane is unlikely to undergo aerobic biodegradation in the environment or in sewage treatment plants.