p-tert-butylstyrene

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:

16 March 2017 - 1 March 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

CAS No.: 1746-23-2
Synonyms: para-tertiary-butyl styrene; TBS
Storage: Stored in refrigerator in original container.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): obtained from the Wareham Wastewater Treatment
Facility, Wareham, Massachusetts. Approximately 2 L was collected.
- Preparation of inoculum for exposure: Activated sludge was passed through a 2-mm stainless steel sieve and then centrifuged at 1000 rpm for ten minutes. The supernatant was kept and solids discarded. The resultant secondary effluent was filtered through coarse filter paper. The secondary effluent filtrate was retained and aerated overnight in an environmental chamger set to maintain a temperature of 20 ± 1 ºC. The inoculum was used one day after preparation.


No additional data

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST DESIGN

- Fifty-four biological oxygen demand (BOD) bottles were prepared for the control, reference substance and test substance.
- Eighteen bottles per treatement.
- Two each for Day 0 and three per sampling intervial.

PREPERATION
- Test solutions were prepared by first adding approximately 6 L of the oxygen-rich water to each of the three Erlenmeyer flasks. One for p-tert-butylstyrene, sodium benzoate and inoculum control.
- Each flask consisted for 6.0 mL of the four nutirent solutions and 0.90 mL of the inoculum.
- Test substance bottle received a final concentration of 2 mg/L; the sodium benzoate bottle received a final concetration of 5mg/L; and the inoculum control remained unfortified.


TEST SYSTEM
- Each solution was siphoned from the flasks into the respective series of 18 BOD bottles. (Total 54 bottles for the three solutions types)
- Once filled, the botles were closed and labeled.
- With exemption of the BOD bottles used for Day 0 analysis, all bottles were placed in the dark in an environmental chamber.
- Four additional BOD bottles were prepared from each set of solutions to provide additional samples for analysis if necessary.

SAMPLING
- Sampling frequency: Day 7, 14, 21 and 28
- Sampling method: Analyzed for oxygen concentration utilizing a Yellow Springs Instrubment (YSI) Pro 20 dissolved oxygen meter.
- Sample storage before analysis: The temperature of the environmental chamber was continuously monitored throughout the exposure period ranging from 19-22°C.

Reference substance:

other: sodium benzoate

Key result

Parameter:

% degradation (DOC removal)

Value:

ca. -2.4

Sampling time:

28 d

Details on results:

Mean dissolved oxygen concentrations in the p-tert-butylstyrene test solutions ranged from 8.9 mg O2/L on Day 0 to 8.4 mg O2/L on Day 28. Biodegradation of -2.4% of ThOD was observed for p-tert-butylstyrene on Day 28.

Results with reference substance:

Dissolved oxygen concentrations for the sodium benzoate solutions decreased from 8.9 mg O2/L on Day 0 to 1.6 mg O2/L on Day 28.

Biodegradation in the sodium benzoate test solutions was 75.6% of ThOD by Day 7, thus meeting the validity criterion of reaching 60% or
greater biodegradation within 28 days. Biodegradation in the sodium benzoate test solutions was 79.2% of ThOD on Day 28, which indicated that the inoculum contained a viable microbial population and that the test procedures used during the study were adequate.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

p-tert-butylstyrene cannot be classified as readily biodegradable under the conditions of this test since it did not achieve ≥60% biodegradation within 28 days.

Executive summary:

As study was conducted to determine the ready biodegradability of the substance according to OECD Guideline 301D, in compliance with GLP. Activated sludge from predominantly domestic origin was exposed to the test substance at an initial concentration of 2 mg/mL. Sodium benzoate was used as the reference substance and the % biodegradation was estimated through measurement of the change in dissolved oxygen concentration. Biodegradation in the sodium benzoate solutions was 75.6% of ThOD by Day 7, thus meeting the validity criterion of reaching 60% or greater biodegradation within 28 days. Biodegradation in the sodium benzoate test solutions was 79.2% of ThOD on Day 28, which indicated that the inoculum contained a viable microbial population and that the test procedures used during the study were adequate. The substance attained -2.4% degradation after 28 d and is not considered to be readily biodegradable under the conditions of OECD Guideline 301D (Smithers Viscient, 2019).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

As study was conducted to determine the ready biodegradability of the substance according to OECD Guideline 301D, in compliance with GLP. Activated sludge from predominantly domestic origin was exposed to the test substance at an initial concentration of 2 mg/mL. Sodium benzoate was used as the reference substance and the % biodegradation was estimated through measurement of the change in dissolved oxygen concentration. Biodegradation in the sodium benzoate solutions was 75.6% of ThOD by Day 7, thus meeting the validity criterion of reaching 60% or greater biodegradation within 28 d. Biodegradation in the sodium benzoate test solutions was 79.2% of ThOD on Day 28, which indicated that the inoculum contained a viable microbial population and that the test procedures used during the study were adequate. The substance attained -2.4% degradation after 28 d and is not considered to be readily biodegradable under the conditions of OECD Guideline 301D (Smithers Viscient, 2019).