S-2-Benzothiazolyl (Z)-2-(2-aminothiazol-4-yl)-2-acetyloxyiminothioacetate

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study with GLP.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge was collected from a sewage treatment works A-2500 Baden, which waste water catchment is predominantly domestic. On arrival in the laboratory, the sample was aerated by means of a filtered compressed air before being used for the study. The suspended solids concentration was determined by filtering a 5 ml sample through a pre-dried and pre-weighed glass filter. The filter with solids were dried at 105 °C and re-weighed and the sludge solids determined by difference.
The inoculum was not acclimatised or adapted to "T15-AE" before exposure to the test substance in this study.

Duration of test (contact time):

28 d

Initial conc.:

15 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The test substance was added directly to two test substance vessels and the one toxicity control vessel in a nominal concentration of 33.76 mg test substance/L medium. This concentration corresponds to nominally 15 mg carbon/L, considering the carbon content of 44.43 %.
Two negative control groups were run simultaneously.

Procedure
Pre-incubation: On Day -1, to all flasks, containing 2400 ml mineral medium each, an appropriate volume of prepared activated sludge was added, to give a concentration of suspended solids of not more than 30 mg/L in the final 3 litres of inoculated mixture.
The vessels were sealed and aerated overnight with CO2-free air to purge the medium of CO2 prior to the beginning of the study.
Apparatus for carbon dioxide scrubbing and a mixture of CO2-free oxygen and CO2-free nitrogen, from gas cylinders, in the correct proportions (20 % O2 : 80 % N2) were used. The air flow was regulated for each vessel individually.
On Day 0, the relevant vessels were opened to make appropriate additions of the test or reference substance. The test substance was added to vessels A and TK, the reference substance was added to vessels PK and TK. The test solutions were continuously stirred during the test. The vessels were incubated in darkness until the end of the study and the medium continually supplied with CO2-free air.
Barium hydroxide was used to trap the CO2 formed by the degradation of the test substance. Three absorption bottles each containing 100 ml of 0.0125 M barium hydroxide solution, were connected in series to each 5-litre flask.
Test duration: 28 days exposure, with measurement of the last sample on Day 29.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

10

Sampling time:

4 d

Remarks on result:

other: mean of 2 runs

Parameter:

% degradation (CO2 evolution)

Value:

19.9

Sampling time:

10 d

Remarks on result:

other: mean of 2 runs

Parameter:

% degradation (CO2 evolution)

Value:

21.3

Sampling time:

20 d

Remarks on result:

other: mean of 2 runs

Parameter:

% degradation (CO2 evolution)

Value:

26.1

Sampling time:

28 d

Remarks on result:

other: mean of 2 runs

Parameter:

% degradation (CO2 evolution)

Value:

53.6

Sampling time:

28 d

Remarks on result:

other: toxicity control

Details on results:

Test substance: The final biodegradation for T15-AE was 26.1 %.

Positive control: The plateau of biodegradation was reached on about Day 10 and the degradation of the positive control substance sodium benzoate exceeded the pass level of 60 % on about Day4.

Toxicity control: Degradation in the toxicity control, which contained sodium benzoate and the test substance, was not indicative of a significant inhibition of the microbial activity by the test substance. The final biodegradation was 53.6 %.

Temperature control: Temperatures recorded were 22.7 ± 0.3 °C.
pH control: No major deviations were seen during the study time. the pH was between 7.4 and 7.6.

Validity of the test: The test is considered to be valid if the difference of extremes of replicate values of the removal of the test substance at the plateau, at the end of the test or at the 10-d window, as appropriate, is less than 20 % and if the percentage degradation of the reference compound has reached the pass levels by day 14.
The percentage degradation of the positive control exceeded 60 % within ten days of first reaching 10 %. The guidelines require that the final cumulative CO2 yield from the blanks should not exceed 120 mg per three litres of medium and that values greater than 210 mg CO2 / 3 L should trigger the critical checking of the experimental techniques. Total mean blank CO2 production in this study was 114.6 mg per 3 litres.
The satisfactory response recorded for the reference substance indicates that the failure of the substance to degrade extensively in this study cannot be attributed to the deficiencies of either the test method or the inoculum.

Results with reference substance:

Points of degradation plot (reference substance):
60.6 % degradation after 4 d
90.7 % degradation after 10 d

Validity criteria fulfilled:

yes

Interpretation of results:

other: biodegradable, but not readily biodegradable.

Conclusions:

The substance is not readily biodegradable. Its biodegradation is 26.1 % within 28 days.

Executive summary:

The biodegradability of the substance was analysed by the determination of carbon dioxide evolution at frequent intervals over a 28 d period. The method used was that described in Part C.4-C of the EC Commission Directive 92/69/EEC and in the OECD Guideline 301B.

The substance is not readily biodegradable. Its biodegradation is 26.1 % within 28 days.

Description of key information

The biodegradability of the substance was analysed by the determination of carbon dioxide

evolution at frequent intervals over a 28 d period. The method used was that described in Part C.4-C of the EC Commission Directive 92/69/EEC and in the OECD Guideline 301B.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

Inherent biodegradable according to the definition of the OECD.Inherent biodegradable: A classification of chemicals for which there is unequivocal evidence of biodegradation (primary or ultimate) in any test of biodegradability