Triboron trimethyl hexaoxide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is inorganic

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study and current standards, sufficiently documented, acceptable for assessment

Qualifier:

according to guideline

Guideline:

other: Standard Methods for the Examination of Water and Wastewater. 1971. 13th Ed. American Public Health Association, New York, NY

Principles of method if other than guideline:

closed bottle test (BOD of THOD)

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
no data

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): domestic wastewater
- Preparation of inoculum for exposure: Settled domestic wastewater was filtered through glass wool and then added (3 mL/bottle) as seed material to clean 300 mL BOD bottles. The bottles were half filled with aerated dilution water containing specified minerals along with buffer.

Duration of test (contact time):

20 d

Initial conc.:

3 mg/L

Based on:

test mat.

Initial conc.:

7 mg/L

Based on:

test mat.

Initial conc.:

10 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Aeration of dilution water: aerated dilution water used at beginning of test; reaeration when DO of test flasks dropped below 4.0 mg/L

TEST SYSTEM
- Method used to create aerobic conditions: A clean, empty BOD bottle and the test bottle were connected with an adapter; by allowing half of the liquid to pass into the new bottle, followed by moderate shaking, the DO level could be returned to about 7 mg/L. Once this reaeration was accomplished, all of the liquid was returned to the original bottle, and a new DO value was determined.
- Measuring equipment: commercial DO meter
- Test performed in closed vessels due to significant volatility of test substance: yes; flask were only opened in order to reaerate samples

SAMPLING
- Sampling frequency: five times during the 20 day test period

Reference substance:

not specified

Preliminary study:

no data

Test performance:

no data

Parameter:

% degradation (O2 consumption)

Value:

76

Sampling time:

5 d

Parameter:

% degradation (O2 consumption)

Value:

88

Sampling time:

10 d

Parameter:

% degradation (O2 consumption)

Value:

91

Sampling time:

15 d

Parameter:

% degradation (O2 consumption)

Value:

95

Sampling time:

20 d

Results with reference substance:

no data

Interpretation of results:

readily biodegradable

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study and current standards, sufficiently documented, acceptable for assessment

Qualifier:

according to guideline

Guideline:

other: Standard Methods for the Examination of Water and Wastewater. 1971. 13th Ed. American Public Health Association, New York, NY

Principles of method if other than guideline:

closed bottle test (BOD of THOD)

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
no data

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment: marine

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):seawater taken from Lavaca Bay, Texas, USA
- Preparation of inoculum for exposure: Seawater seed source was maintained by adding small amounts of settled raw wastewater about every 3 to 4 days as a source of substrate, seed bacteria, and growth factors.

Duration of test (contact time):

20 d

Initial conc.:

3 mg/L

Based on:

test mat.

Initial conc.:

7 mg/L

Based on:

test mat.

Initial conc.:

10 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Aeration of dilution water: aerated dilution water used at beginning of test; reaeration when DO of test flasks dropped below 4.0 mg/L

TEST SYSTEM
- Method used to create aerobic conditions: A clean, empty BOD bottle and the test bottle were connected with an adapter; by allowing half of the liquid to pass into the new bottle, followed by moderate shaking, the DO level could be returned to about 7 mg/L. Once this reaeration was accomplished, all of the liquid was returned to the original bottle, and a new DO value was determined.
- Measuring equipment: commercial DO meter
- Test performed in closed vessels due to significant volatility of test substance: yes; flask were only opened in order to reaerate samples

SAMPLING
- Sampling frequency: five times during the 20 day test period

Reference substance:

not specified

Preliminary study:

no data

Test performance:

no data

Parameter:

% degradation (O2 consumption)

Value:

69

Sampling time:

5 d

Parameter:

% degradation (O2 consumption)

Value:

84

Sampling time:

10 d

Parameter:

% degradation (O2 consumption)

Value:

85

Sampling time:

15 d

Parameter:

% degradation (O2 consumption)

Value:

97

Sampling time:

20 d

Results with reference substance:

no data

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Description of key information

TMBX readily hydrolyses to form methanol and boric acid, both of which are toxicologically significant species and the ready biodegradation of these breakdown products should instead be considered. Being an inorganic substance, boric acid is not readily biodegradable.

Ready biodegradability of methanol was assessed in separate studies with both freshwater and seawater inoculum (Price et al 1974). Using settled and filtered domestic waste water, methanol was found to be readily biodegradable with 88% and 95% at 10 and 20 days respectively when measured by O2 consumption. Similar results were obtained when using seawater as the inoculum with 84% and 97% degradation at 10 and 20 days respectively.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

marine water