Flucytosine

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-09-30 - 2003-11-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Flucytosine

EC Number:

217-968-7

EC Name:

Flucytosine

Cas Number:

2022-85-7

Molecular formula:

C4H4FN3O

IUPAC Name:

flucytosine

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Please refer to Test material information

Study design

Oxygen conditions:

aerobic

Remarks:

no aeration

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): Supernatant from settled domestic activated sludge, Source: Galt Wastewater Treatment Plant, Cambridge, Ontario, Canada
Date Collected: 2003-10-31
Date Used: 2003-10-31
- Inoculum concentration: Approximately 1.0 mL/L

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

7.17 mg/L

Based on:

ThOD

Remarks:

Based on molecular weight, the calculated ThOD was 0.56 mg O2/mg substance.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium, pH 7.2
- Additional substrate: reference substrate for inhibition testing: phthalic acid
- Solubilising agent (type and concentration if used): Dilution water: Deionized water with nutrients
- Test temperature: 22 +/- 2 °C
- pH: 7.4 +/- 0.2
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Non-renewal, closed bottle; Glass, with ground glass stoppers and plastic seals; Test volume: 300 ml
- Number of culture flasks/concentration: 2 replicates
- Measuring equipment: Oxygen electrode

SAMPLING
- Sampling frequency: 7 day interval

CONTROL AND BLANK SYSTEM
- Toxicity control: reference substrate for inhibition testing: phthalic acid; Reference Concentration: 2.76 mg/L; ThOD Reference Substance: 1.44 mg ThOD/mg reference substance

STATISTICAL METHODS:
The amount of oxygen consumed within the test system is compared ‘to the ThOD of the test item and the percent (%) degradation is calculated as follows:
((mg/L O2 uptake at time = t (in days)) / (mg/L Test Item (as ThOd)) x 100% = % degradation over time
Using this method, the extent and rate of biodegradability is determined based on the cumulative uptake of molecular oxygen. Test items exhibiting a biochemical oxygen demand (BOD) of > 60% of the total oxygen demand (based on ThOD) in a 28-day period are considered to be readily biodegradable (OECD, 1992). Additionally, the test item must achieve 60% biodegradation within 14 days of attaining 10% biodegradation (this criterion is referred to as the "fourteen-day window”).

Reference substance

Reference substance:

other: Phthalic Acid, ACS, 99.5+% (Assay)

Remarks:

CAS # 88-99-3, Lot Number: C14K39, Chemical Name/Synonym: 1,2-Benzenedicarboxylic acid; o-dicarboxybenzene Chemical Formula: C6H4(COOH)2

Results and discussion

Test performance:

A reference substance testing was conducted in parallel with the definitive test to demonstrate consistency in laboratory test performance that might be affected by such factors as inoculum quality and performance of technical staff. The reference substance used in this study was phthalic acid.
REFERENCE TEST: Passed (i.e., ≥60% degradation in 14 days).
INHIBITION TEST: 7.17 mg/l test substance, 2.76mg/l reference substance; Inhibition not observed (i.e., >25% degradation)
The reference substance test passed the criteria for acceptability of the results.

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

0 d

% Degradation 2

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

7 d

% Degradation 3

Key result

Parameter:

% degradation (O2 consumption)

Value:

-1.2

Sampling time:

14 d

% Degradation 4

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

21 d

% Degradation 5

Key result

Parameter:

% degradation (O2 consumption)

Value:

1.2

Sampling time:

28 d

Details on results:

The test item is not readily biodegradable (i.e., < 60% degradation in 28 days).

Any other information on results incl. tables

REFERENCE SUBSTANCE AND INHIBITION DATA

Reference: Phthalic Acid

Day	0	7	14	21	28
Reference, % degradation at time = x	0.0	71.7	88.1	88.1	94.4
Inhibition,  % degradation at time = x	0.0	>25	>25	>25	>25

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test item is not readily biodegradable (i.e., <60% degradation in 28 days). The test item is not inhibitory on the degradation of phthalic acid.