Reaction mass of octan-2-ylbenzene, octan-3-ylbenzene and octan-4-ylbenzene

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06 May - 06 June 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

adopted July 17, 1992

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Treatment:Freshly obtained sludge was kept under continuous aeration until further treatment. Before use, sludge was coarsely sieved (1 mm). After treatment concentration of suspended solids (SS) was determined to be 3.1 g/L in concentrated sludge as used for the test. Magnetically stirred sludge was used as inoculum at an amount of 3 mL per litre of mineral medium, leading to a SS concentration of 9.4 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

14 mg/L

Based on:

test mat.

Initial conc.:

12 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: 1 litre mineral medium contains: 10 ml of solution (A), 1 ml of solutions (B) to (D) and Milli-RO water
Stock solutions of mineral components
A) 8.50 g KH2PO4; 21.75 g K2HPO4; 67.20 g Na2HPO4.12H2O; 0.50 g NH4Cl; dissolved in Milli-Q water and made up to 1 litre, pH 7.4 ± 0.2
B) 22.50 g MgSO4.7H2O dissolved in Milli-Q water and made up to 1 litre.
C) 36.40 g CaCl2.2H2O dissolved in Milli-Q water and made up to 1 litre.
D) 0.25 g FeCl3.6H2O dissolved in Milli-Q water and made up to 1 litre.
- Test temperature: between 22 and 23°C
- pH: At t=0 d: 7.5 - 7.6; At t=14d (procedure and toxicity control) 7.8 - 7.9; At t=28 d: 7.6 – 7.9 (blank control and test solution)
- pH adjusted: no
- Aeration: Constant aeration with a mixture of oxygen (ca. 20%) and nitrogen (ca. 80%)
- Suspended solids concentration: suspended solids (SS) was determined to be 3.1 g/L in concentrated sludge as used for the test. Magnetically stirred sludge was used as inoculum at an amount of 3 mL per litre of mineral medium, leading to a SS concentration of 9.4 mg/L
- Illumination: Test media were excluded from light.
- Pre-incubation medium: The day before the start of the test (day -1) mineral components, Milli- RO water (ca. 80% of final volume) and inoculum were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.


TEST SYSTEM
- Culturing apparatus: 2 litre brown coloured glass bottles.
- Type and number of bottles:
Test suspension: containing test item and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Procedural control: containing procedural control item and inoculum (1 bottle).
Toxicity control: containing test item, procedural control item and inoculum (1 bottle).
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used: Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle.

SAMPLING
- Sampling frequency: Titration were made on day 2, 5, 8, 12, 15, 19, 23 and 29
- Sampling method: Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers were moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes

PREPARATION OF TEST SOLUTION
SHR 1396 was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L. At the start of the test the molecular formula and molecular weight was unknown. A sample of test item was taken for determination of Total Organic Carbon (TOC) content. TOC content of the test item was determined to be 86.53%. This was confirmed by a TOC of 88.34%, calculated from the molecular formula. The test item was tested in duplicate at a target concentration of 14 mg/L, corresponding to 12 mg TOC/L.
On the day of testing weighed amounts of test item were added to 2 L test bottles containing medium with microbial organisms and mineral components (test item bottle A: 28.70 mg; test item bottle B: 28.07 mg; toxicity control bottle: 27.61 mg). To this end, small watch glasses were used to transfer weighed amounts of test item to respective test bottles. Test solutions were continuously stirred during the test, to ensure optimal contact between test item and test organisms.

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

1

Sampling time:

29 d

Key result

Parameter:

% degradation (CO2 evolution)

Value:

9

Sampling time:

29 d

Details on results:

- ThCO2 of SHR 1396 was calculated to be 3.17 mg CO2/mg
- Relative biodegradation values calculated from measurements performed during the test period revealed no biologically relevant biodegradation of SHR 1396 (1% and 9%, based on ThCO2).
In the toxicity control, more than 25% biodegradation occurred within 14 days (40%, based on ThCO2). Therefore, the test item was assumed not to inhibit microbial activity.
Functioning of the test system was checked by testing the procedural control item sodium acetate, which showed a normal biodegradation curve

Results with reference substance:

Procedural control item was biodegraded by at least 60% (actual result: 86%) within 14 days.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

SHR 1396 was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Executive summary:

In a CO2 Evolution Test performed according to OECD guideline 301B and GLP principles, the substance was evaluated for its ready biodegradability. The test was performed in an aerobic aqueous medium containing activated sludge over a period of 28 days. The test item was tested in duplicate at a target concentration of 14 mg/L, corresponding to 12 mgTOC/L. Additionally two innoculum blanks, one procedure control and one toxicity control were tested. Relative biodegradation values calculated from measurements performed during the test period revealed nobiologically relevantbiodegradation of SHR 1396 (1% and 9%, based on ThCO2). The relative biodegradation in the toxicity controle was 40% (based on ThCO2) within 14 days. Therefore, the test item was assumed not to inhibit microbial activity.

All criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, SHR 1396 was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Description of key information

SHR 1396 was not readily biodegradable under the conditions of the performed modified Sturm test.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

In a CO2 Evolution Test performed according to OECD guideline 301B and GLP principles, the substance was evaluated for its ready biodegradability. The test was performed in an aerobic aqueous medium containing activated sludge over a period of 28 days. The test item was tested in duplicate at a target concentration of 14 mg/L, corresponding to 12 mg TOC/L. Additionally two innoculum blanks, one procedure control and one toxicity control were tested. Relative biodegradation values calculated from measurements performed during the test period revealed no biologically relevant biodegradation of SHR 1396 (1% and 9%, based on ThCO2). The relative biodegradation in the toxicity control was 40% (based on ThCO2) within 14 days. Therefore, the test item was assumed not to inhibit microbial activity.

All criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, SHR 1396 was not readily biodegradable under the conditions of the modified Sturm test presently performed.