Indole

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

Data is from peer reviewed journal and authoritative databases

Qualifier:

according to guideline

Guideline:

other: as mentioned below

Principles of method if other than guideline:

Biodegradation study was conducted for evaluating the degradability of the test chemical in freshwater sediment.

GLP compliance:

not specified

Radiolabelling:

no

Oxygen conditions:

anaerobic

Inoculum or test system:

natural sediment: freshwater

Details on source and properties of sediment:

- Details on collection (e.g. location, sampling depth, contamination history, procedure): Freshwater sediments were collected from Buffalo Run stream (Bellefonte, Pa.).

Duration of test (contact time):

35 d

Initial conc.:

> 32 - < 50 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salt medium was used as a test medium for the study.
- Additional substrate: 1.2 mg of Na2HCO3 and 0.12 mg of Na2S 9H20 per ml were added as an additional substrate in the test medium.
- Test temperature: 22°C
- pH: 7.0
- pH adjusted: yes, pH was adjusted with a solution of HCl.
- Continuous darkness: yes
- Other: After test medium has been autoclaved for 15 min to remove 02, the medium was maintained under a positive pressure of N2 gas which was previously passed through copper filings at 300°C to remove traces of O2. Test chemical was added to the medium when the medium temperature had cooled to 50°C.

TEST SYSTEM
- Culturing apparatus: Serum bottles of 160 ml volume was used as a test vessel.
- Number of culture flasks/concentration: Triplicates
- Test performed in closed vessels due to significant volatility of test substance: yes, test vessel was closed with butyl rubber stoppers and aluminum crimp seals.
- Test performed in open system: no, test was not performed in open system.

CONTROL AND BLANK SYSTEM
Controls were also run simultaneously during the study.

Reference substance:

not specified

Remarks on result:

other: Details not known

Key result

% Degr.:

100

Parameter:

test mat. analysis

Remarks:

(% degradation)

Sampling time:

33 d

Remarks on result:

other: Other details not known

Key result

Remarks on result:

other: Details not known

Transformation products:

yes

No.:

#1

Details on transformation products:

- Formation and decline of each transformation product during test: As the test chemical disappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks. Subsequently, oxindole was eliminated by the inocula over 110 days.

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

Validity criteria fulfilled:

not specified

Conclusions:

The percentage degradation of test chemical was determined to be 100% after a period of 33 days. During the degradation study, as the test chemical disappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks. Subsequently, oxindole was eliminated by the inocula over 110 days.

Executive summary:

Biodegradation study in sediment was conducted for a period of 35 days under anaerobic conditions for evaluating the degradability of the test chemical in freshwater sediment.Freshwater sediments collected from Buffalo Run stream (Bellefonte, Pa.) were used as a test inoculum. Test chemical concentration used for the study was in the range of 32 to 50 mg/l (0.27 to 0.43 mmol/l). Serum bottles of 160 ml volume was used as a test vessel. Test vessel was closed with butyl rubber stoppers and aluminum crimp seals. Mineral salt medium was used as a test medium for the study. 1.2 mg of Na2HCO3 and 0.12 mg of Na2S 9H20 per ml were added as an additional substrate in the test medium. After test medium has been autoclaved for 15 min to remove 02, the medium was maintained under a positive pressure of N2 gas which was previously passed through copper filings at 300°C to remove traces of O2. Freshwater sediment was diluted with media, stirred vigorously, and dispensed as slurries to N2-flushed serum bottles (160 ml). Test chemical was added to the medium when the medium temperature had cooled to 50°C. The pH of the medium was 7.0 which was adjusted with a solution of HCl. Later, 100 ml portions of inoculated medium were dispensed to N2-flushed serum bottles. Control bottles were sterilized by being autoclaved on three successive days. All bottles were incubated stationary in the dark at a temperature of 22°C for a period of 35 days. All experiments were performed in triplicates, Additional bottles were frozen after various time intervals for subsequent chemical analysis. The disappearance of test chemical in test sludge was monitored by HPLC. The percentage degradation of test chemical was determined to be 100% after a period of 33 days, respectively. As the test chemical disappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks. Subsequently, oxindole was eliminated by the inocula over 110 days. This, indicates that test chemical is not persistent in sediment and the exposure to sediment dwelling animals is moderate to low.

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

Data is from computational model developed by USEPA

Qualifier:

according to guideline

Guideline:

other: Modeling database

Principles of method if other than guideline:

Estimation of the half-life value of test chemical in water. The estimations were done using the Fugacity Model of the Estimation Programs Interface (EPI) Suite v.4.1 program developed by the U. S. Environmental Protection Agency's. The Fugacity Model in EPI suite is a level III multimedia fate model and predicts the half-life and partitioning of an organic compound in an evaluative environment mainly between four main compartments; that is, air, water, sediment and soil.

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

other: estimation

Inoculum or test system:

not specified

Parameter followed for biodegradation estimation:

test mat. analysis

Compartment:

water

% Recovery:

24.8

Remarks on result:

other: Other details not known

Key result

% Degr.:

50

Parameter:

other: Half-life in water

Sampling time:

15 d

Remarks on result:

other: Other details not known

Key result

Compartment:

water

DT50:

15 d

Type:

other: estimated data

Temp.:

25 °C

Remarks on result:

other: Other details not known

Transformation products:

not specified

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

	Mass Amount (percent)	Half-Life (hr)	Emissions (kg/hr)
Water	24.8	360	1000

 

	Fugacity (atm)	Reaction (kg/hr)	Advection (kg/hr)	Reaction (percent)	Advection (percent)
Water	7.77e-012	665	345	22.2	11.5

Validity criteria fulfilled:

not specified

Conclusions:

Estimated half life of test chemical in water was 15 days (360 h).

Executive summary:

Estimation Programs Interface prediction model was run to predict the half-life in water for the test chemical. If released in to the environment, 24.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low.

Reference 3

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

Data is from computational model developed by USEPA

Qualifier:

according to guideline

Guideline:

other: Modeling database

Principles of method if other than guideline:

Estimation of the half-life value of test chemical in sediment. The estimations were done using the Fugacity Model of the Estimation Programs Interface (EPI) Suite v.4.1 program developed by the U. S. Environmental Protection Agency's. The Fugacity Model in EPI suite is a level III multimedia fate model and predicts the half-life and partitioning of an organic compound in an evaluative environment mainly between four main compartments; that is, air, water, sediment and soil.

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

other: estimation

Inoculum or test system:

not specified

Parameter followed for biodegradation estimation:

test mat. analysis

Compartment:

sediment

% Recovery:

0.761

Remarks on result:

other: Other details not known

Key result

% Degr.:

50

Parameter:

other: Half-life in sediment

Sampling time:

135 d

Remarks on result:

other: Other details not known

Key result

Compartment:

sediment

DT50:

135 d

Type:

other: estimated data

Temp.:

25 °C

Remarks on result:

other: Other details not known

Transformation products:

not specified

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

	Mass Amount (percent)	Half-Life (hr)	Emissions (kg/hr)
Sediment	0.761	3240	0

 

	Fugacity (atm)	Reaction (kg/hr)	Advection (kg/hr)	Reaction (percent)	Advection (percent)
Sediment	5.59e-012	2.26	0.212	0.0754	0.00705

Validity criteria fulfilled:

not specified

Conclusions:

Estimated half life of test chemical in sediment estimated to be 135 days (3240 h).

Executive summary:

Estimation Programs Interface prediction model was run to predict the half-life in sediment for the test chemical. The half-life period of test chemical in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.761%), indicates that test chemical is not persistent in sediment.

Description of key information

Biodegradation study in sediment was conducted for a period of 35 days under anaerobic conditions for evaluating the degradability of the test chemical in freshwater sediment (from peer reviewed journal (E. L. Madsen et. al., 1988) and authoritative databases). Freshwater sediments collected from Buffalo Run stream (Bellefonte, Pa.) were used as a test inoculum. Test chemical concentration used for the study was in the range of 32 to 50 mg/l (0.27 to 0.43 mmol/l). Serum bottles of 160 ml volume was used as a test vessel. Test vessel was closed with butyl rubber stoppers and aluminum crimp seals. Mineral salt medium was used as a test medium for the study. 1.2 mg of Na2HCO3 and 0.12 mg of Na2S 9H20 per ml were added as an additional substrate in the test medium. After test medium has been autoclaved for 15 min to remove 02, the medium was maintained under a positive pressure of N2 gas which was previously passed through copper filings at 300°C to remove traces of O2. Freshwater sediment was diluted with media, stirred vigorously, and dispensed as slurries to N2-flushed serum bottles (160 ml). Test chemical was added to the medium when the medium temperature had cooled to 50°C. The pH of the medium was 7.0 which was adjusted with a solution of HCl. Later, 100 ml portions of inoculated medium were dispensed to N2-flushed serum bottles. Control bottles were sterilized by being autoclaved on three successive days. All bottles were incubated stationary in the dark at a temperature of 22°C for a period of 35 days. All experiments were performed in triplicates, Additional bottles were frozen after various time intervals for subsequent chemical analysis. The disappearance of test chemical in test sludge was monitored by HPLC. The percentage degradation of test chemical was determined to be 100% after a period of 33 days, respectively. As the test chemical disappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks. Subsequently, oxindole was eliminated by the inocula over 110 days. This, indicates that test chemical is not persistent in sediment and the exposure to sediment dwelling animals is moderate to low.

Additional information

Experimental study and predicted data of the test chemical were reviewed for the biodegradation in water & sediment end point which are summarized as below:

 

In an experimental study from peer reviewed journal (E. L. Madsen et. al., 1988) and authoritative databases, biodegradation study in sediment was conducted for a period of 35 days under anaerobic conditions for evaluating the degradability of the test chemical in freshwater sediment. Freshwater sediments collected from Buffalo Run stream (Bellefonte, Pa.) were used as a test inoculum. Test chemical concentration used for the study was in the range of 32 to 50 mg/l (0.27 to 0.43 mmol/l). Serum bottles of 160 ml volume was used as a test vessel. Test vessel was closed with butyl rubber stoppers and aluminum crimp seals. Mineral salt medium was used as a test medium for the study. 1.2 mg of Na2HCO3 and 0.12 mg of Na2S 9H20 per ml were added as an additional substrate in the test medium. After test medium has been autoclaved for 15 min to remove 02, the medium was maintained under a positive pressure of N2 gas which was previously passed through copper filings at 300°C to remove traces of O2. Freshwater sediment was diluted with media, stirred vigorously, and dispensed as slurries to N2-flushed serum bottles (160 ml). Test chemical was added to the medium when the medium temperature had cooled to 50°C. The pH of the medium was 7.0 which was adjusted with a solution of HCl. Later, 100 ml portions of inoculated medium were dispensed to N2-flushed serum bottles. Control bottles were sterilized by being autoclaved on three successive days. All bottles were incubated stationary in the dark at a temperature of 22°C for a period of 35 days. All experiments were performed in triplicates, Additional bottles were frozen after various time intervals for subsequent chemical analysis. The disappearance of test chemical in test sludge was monitored by HPLC. The percentage degradation of test chemical was determined to be 100% after a period of 33 days, respectively. As the test chemical disappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks. Subsequently, oxindole was eliminated by the inocula over 110 days. This, indicates that test chemical is not persistent in sediment and the exposure to sediment dwelling animals is moderate to low.

 

For the test chemical, Estimation Programs Interface prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment, 24.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of test chemical in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.761%), indicates that test chemical is not persistent in sediment.

 

Thus, on the basis of this available information, test chemical was considered to be not persistent in sediment.

 

In addition to this, biodegradation in water and sediment endpoint can also be considered for waiver as per in accordance with column 2 of Annex IX of the REACH regulation, testing for this end point is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable in water.