Fusidic acid

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:

22 May 2019 - 11 November 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)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Source and lot/batch number of test material: A90326 (CoA)
- Expiration date of the lot/batch: 31 December 2019
- Purity test date: 15 January 2019
- Form: White crystalline powder
- Purity: 100% (CoA)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Cold, 2-8°C, well-closed container protected from light (CoA)
- Stability: The substance is not reactive. Protect from light.

FORM AS APPLIED IN THE TEST (if different from that of starting material)
In stock solution of water

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Remarks:

STP Ruhrverband Kläranlage, Schmallenberg, Germany. Mainly fed by municipal wastewater

Details on inoculum:

Washed with mineral medium after arrival. Kept aerobic until use. The sludge was left for settlement. The supernatant was discarded and concentration of suspended solids was measured. The sludge was suspended in mineral medium (Concentration 1-3 g suspended solids/L). The sludge was aerated with CO2-free air for two days to purge the system of carbon dioxide. Dry weight was determined in a subsample. Concentration used was 29.6 mg dry mass/L.

Duration of test (contact time):

28 d

Initial conc.:

15 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Parameter followed for biodegradation estimation:

inorg. C analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium
( a ) KH2PO4 8.50 g/L
K2HPO4 21.75 g/L Na2HPO4 26.64 g/L
NH4Cl 0.50 g/L
The pH value of the solution was 7.4.
( b ) CaCl2 x 2 H2O 36.40 g/L
( c ) MgSO4 x 7 H2O 22.50 g/L
( d ) FeCl3 x 6 H2O 0.25 g/L.
The mineral medium applied in the test contained 10 mL/L and 1 mL/L of the mineral stock solution a and b–d, respectively.
- Test temperature: 22°C (± 2°C)
- pH: 7.4
- pH adjusted: yes before test start
- Aeration of dilution water: For the test deionized water, free from inhibitory concentrations of toxic substances (e.g. Cu2+ ions) and with a content of less than 2 mg/L TOC was used
- Suspended solids concentration: The concentration used in the test was 29.6 mg dry mass/L
- Continuous darkness: no - in diffuse light

TEST SYSTEM
- Culturing apparatus: 5-litre Erlenmeyer flasks
- Number of culture flasks/concentration:
Background control: 1 vessel containing mineral medium only
Inoculum blank: 2 vessels containing inoculated mineral medium
Test suspension: 2 vessels containing test item (15 mg DOC/L) and inoculum
Procedural control: 1 vessel containing reference item (21 DOC mg/L) and inoculum
Toxicity control: 1 vessel containing test item (15 mg DOC/L), reference item (21 mg DOC/L) and inoculum

- Details of trap for CO2 and volatile organics if used: The CO2 is trapped in sodium hydroxide and is measured as inorganic carbon.

- Days of sampling for IC measurement were day 0, 3, 7, 10, 14, 21, 24, 28 and 31.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (inorg. C analysis)

Value:

94.3

St. dev.:

1.8

Sampling time:

28 d

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

According to the ready biodegradability test OECD 301B (Fraunhofer Institute, 2019), 86% was degraded at the end of the 10-day window, with a 94% degradation at test end. Na-fusidin is therefore classified as readily biodegradable.

Executive summary:

The biodegradation of sodium fusidate was investigated in a CO2 Evolution test according to OECD Guideline 301B with no deviations. The validity criteria of the test were fulfilled.

The biodegradation of sodium fusidate in the CO2 evolution test was found to be 94% after 28 days. Biodegradation within the 10-day-window was found to be 86%. Therefore, sodium fusidate is considered as being readily biodegradable under the chosen test conditions.

Description of key information

According to the ready biodegradability test OECD 301B (Fraunhofer Institute, 2019), 86% was degraded at the end of the 10 -day window, with a degradation of 94% at test end. Sodium fusidate is therefore classified as readily biodegradable.

For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater