Hydroquinone

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

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:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

mixture of sewage, soil and natural water

Details on inoculum:

- inoculum samples collected in the closer surroundings of the investigating laboratory;
- sludge concentration: 30 mg/l;
- biodegradation was determined on the basis of DOC and BOD measurements after 14 days

Duration of test (contact time):

14 d

Initial conc.:

50 mg/L

Based on:

DOC

Parameter:

% degradation (DOC removal)

Value:

86

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

70

Sampling time:

14 d

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Principles of method if other than guideline:

The test was conducted in accordance with 'Biodegradation test of chemical substance by microorganisms etc.' stipulated in the Order Prescribing the Items of the Test Relating to the new Chemical Substance (1974, Order of the Prime Minister, the Minister of Health and Welfare, the Minister of International Trade and Industry No. 1). This guideline corresponds to '301C, Ready Biodegradability: Modified MITI Test I' stipulated in the OECD Guidelines for Testing of Chemicals (May 12, 1981).

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sludge was sampled at the following locations in Japan: Fukogawa city sewage plant, Fukashiba industry sewage plant, Nakahama city sewage plant, Ochiai city sewage plant, Kitakami river, Shinano river, Yoshino river, Lake Biwa, Hiroshima bay, and Dookai bay; sludge collected at March, June, and December in every year; city sewage: returned sludge of sewage plants were collected; rivers, lake and sea: surface water and surface soil which is in contact with atmosphere were collected
- Laboratory culture: no
- Method of cultivation: 5 L of the filtrate of the supernatant of an activated sludge in the present use was mixed with 500 mL of the filtrate of the supernatant of a newly collected sludge respectively and the mixture was cultured at pH 7.0 +/- 1 under the sufficient aeration (aeration: prefiltered open air was used). Ca. 30 min after ceasing the aeration, supernatant corresponding to ca. 1/3 of the whole volume was removed. The equal volume of dechlorinated water was added to the remaining portion and aerated again, followed by addition of synthetic sewage (glucose, peptone and monopotassium phosphate were dissolved in dechlorinated water, respectively, each concentration of them was to be 5% ( w/v) and the solution was adjusted to pH 7.0 +/- 1.0 with sodium hydroxide), concentrations of that portion was to be 0.1% (w/v). This procedure was repeated once every day. The culturing was carried out at 25 +/- 2°C.
- Preparation of inoculum for exposure: 30 mg/L sludge were added to test vessels containing 300 mL of basal culture medium and 100 mg/L test substance, containing 300 mL of basal culture medium and 30 mg/L aniline (reference substance), and containing 300 mL of basal culture medium and no test substance and no reference substance
- Pretreatment: not reported
- Concentration of sludge: 30 mg/L

Duration of test (contact time):

14 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: not reported (preparation conducted according to JIS K 0102-1986-21)
- Additional substrate: no
- Solubilising agent (type and concentration if used): not reported; acetophenone, however, is well soluble in water; ws: ca. 5000 mg/L)
- Test temperature: 25 +/- 1°C
- pH: 7.0 +/- 1 (pH relates to basal medium and sludge culture medium; pH of test solutions were measured, but not reported)
- pH adjusted: not reported for the test solutions (pH of the basal medium and the sludge culture medium were adjusted)
- Aeration of dilution water: not reported
- Suspended solids concentration: 30 mg/L
- Continuous darkness: not reported

TEST SYSTEM
- Culturing apparatus: BOD bottle (closed test vessel: 300 mL)
- Number of culture flasks/concentration: not reported
- Method used to create aerobic conditions: not reported
- Measuring equipment: closed system oxygen consumption measuring apparatus (Coulometer: Ohkura Electric Co., Ltd.)
- Test performed in closed vessels: yes

SAMPLING
- Sampling frequency: after termination of the test
- Sampling method: not reported
- Sample storage before analysis: not reported
- Other: after termination of the test, total organic carbon and the test substance in the test solution were determined (not further specified); pH of the test solutions were measured


CONTROL AND BLANK SYSTEM
- Inoculum blank: performed
- Abiotic control: performed
- Toxicity control: not performed
- Other: biodegradation of reference substance was measured (activity control)

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

70

Sampling time:

14 d

Remarks on result:

other: test substance proved to be readily biodegradable and fulfilling the 14 d window criterion

Details on results:

In the study conducted according to OECD Guideline 301C, hydroquinone proved to be readily biodegradable and fulfilling the 14 d window criterion (70% biodegradation after 14 d).

Results with reference substance:

not reported

The ready biodegradability of hydroquinone was investigated in a study conducted according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)). Hydroquinone proved to be readily biodegradable and fulfilling the 14 d window criterion (70% biodegradation after 14 d).

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

In the study conducted according to OECD Guideline 301C, hydroquinone proved to be readily biodegradable and fulfilling the 14 d window criterion (70% biodegradation after 14 d).

Executive summary:

The ready biodegradability of hydroquinone was investigated in a study conducted according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) over a period of 28 days and using activated sludge as inoculum. The biodegradation rate was determined by measurement of oxygen consumption. Inoculum blank and procedural/functional control with the reference substance aniline were performed.

Hydroquinone proved to be readily biodegradable and fulfilling the 14 d window criterion (70% biodegradation after 14 d).

Description of key information

In  standard guideline tests Hydroquinone proved to be readily biodegradable. Also under anaerobic conditions the substance is completely metabolized.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

In studies conducted according to OECD Guideline 301C (MITI I), hydroquinone proved to be readily biodegradable, fulfilling the 14 d window criterion (70% biodegradation after 14 d). Under aerobic conditions, 1,4-benzoquinone, 2-hydroxy-1,4-benzoquinone, and β-ketoadipic acid were identified as metabolic intermediates, however at low concentrations.

Proposed metabolism pathway under anaerobic conditions: degradation via phenol, cyclohexanol, cyclohexanone to caproic and adipic acid which are further degraded to acetate, propionate, butyrate, CO₂, H₂and CH₄.