2,5-di-tert-pentylhydroquinone

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well-performed non-GLP study. The study was identified as an inherent biodegradability test because the applied inoculum was pre-adapted to the test compound and the incubation exceeded the standard of 28 days in ready biodegradability tests.

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

inoculum was pre-adapted to test compound

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

other: mixture of soil, raw sewage, and activated sludge

Details on inoculum:

- acclimation of inocolum:
* over 14-d period
* stepwise addition of test compound, no details available on added concentrations

Duration of test (contact time):

28 d

Initial conc.:

20.2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: a minimal salts medium
- Test temperature: room temperature
- Aeration of dilution water: the mixture of inoculum and medium was aerated with 70 % oxigen in nitrogen before addition of the test compound
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: fluted 2-L Erlenmeyer flask
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: no data
- Details of trap for CO2 and volatile organics if used: an open reservoir containing 10 mL of 0.15 N barium hydroxide is suspended via a glass tube inserted in a neoprene stopper.
- Barium hydroxide solutions were analyzed by titration with standard 0.1 N HCl to pH 8.5 using a Fisher Automatic Titrimeter II Titration System.
- Present Carbon (% C) was determined by means of a Perkin-Elmer Model 240 Elemental Analyzer.

SAMPLING
- Sampling frequency: no data
- Sampling method: Provisions for removal and addition of the barium hydroxide and for sampling the aqueous media are provided. Fresh barium hydroxide is added bac at each sampling point.

CONTROL AND BLANK SYSTEM
- control: assumed inoculum without test compound
- positive control: sodium citrate, 50.0 mg/L, in duplicate or triplicate

Flasks were sealed and agitated on a rotary shaker.

Reference substance:

other: sodium citrate

Key result

Parameter:

% degradation (CO2 evolution)

Value:

1

St. dev.:

1

Sampling time:

38 d

Remarks on result:

other: Range: 0-3%

Details on results:

- results from triplicate flasks gave good agreement

Results with reference substance:

- 105 % after 38 days

Validity criteria fulfilled:

not specified

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Reliable study (Klimisch 2) indicating that extensive ultimate biodegradation in the environment is unlikely to occur or that the rate of mineralization will be relatively slow.

Description of key information

The key result for biodegradation was derived from an inherent biodegradation study and indicates no biodegradation in water under the given test conditions.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Biodegradation of 2,5-bis(1,1-dimethylpropyl)benzene-1,4-diol was investigated in one study. This reliable study (Saeger, VW, MS-80-SS-42) indicated that the rate of mineralization can be expected to be relatively slow and that extensive ultimate biodegradation in the environment is unlikely to occur. In addition, results from the predictive models in BIOWIN indicate degradation can be assumed to happen very slow. Therefore, 2,5-bis(1,1-dimethylpropyl)benzene-1,4-diol should be considered not readily nor inherently biodegradable and further testing is not required.