Avermectin A1a, 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

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:

From Aug 24 to Sep 25, 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No.: DOA0141202
Purity: 96.6%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): a sewage plan treating predominantly domestic sewage (Nanjing Chengdong Sewage treatment plant).
- Preparation of inoculum for exposure: On the day of test, the test inoculum was prepared by filtering the sample of sewage effluent through a coarse filter, (discarding the first 200 mL) and collecting the remaining filtrates.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST SYSTEM
- Culturing apparatus: BOD bottles
1) Inoculum control: containing inoculum only (1 mL/L);
2) Test: containing test substance (2 mg/L) and inoculum (1 mL/L);
3) Procedure control: containing reference substance (2 mg/L) and inoculum (1 mL/L);
4) Toxicity control: containing test substance (2 mg/L), reference substance (2 mg/L) and inoculum (1 mL/L).
The BOD bottles were fully filled (30 mL) with the aeratedd test medium using a hose which reached down to the bottom of bottle to achieve adequate mixing. Each bottle was filled to ensure that no air bubbles were enclosed.
Bottle numbers of each group: 4 bottles for toxicity control, 20 bottles for inoculum control, 20 bottles for test group, and 20 bottles for reference control.
- Measuring equipment: BOD bottle, pH meter, Dissolved oxygen meter


SAMPLING
- Sampling frequency:
The concentrations of dissolved oxygen in duplicate vessels of each group were determined after addition of prepared solutions to BOD bottles (0 d). Subsequent determinations of concentration of dissolved oxygen for each group, except toxicity control, were made on 0, 2, 5, 7, 11, 14, 18, 21, 25 and 28 d.
The pH and temperature of contents of each bottle were measured after concentration of dissolved oxygen had been determined.
Determinations of DO, pH and temperature in toxicity control group were made at start and after 14 days.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

25.5

Sampling time:

28 d

Details on results:

Oxygen consumption in inoculated blanks was 1.35 mgO2/L after 14 days of incubation, meeting test criteria of less than 1.5 mg O2/L. Degradation in toxicity control was 34.3% after 14 days, meeting test criteria of no less than 25% in 14 days.
Test result indicated the test substance was not toxic to the inoculum. The lowest level of dissolved oxygen in test substance group was 6.46 mg O2/L, which did not fall below 0.5 mg O2/L and difference of biodegradation of test item in two replicates was less than 20%.

Results with reference substance:

The biodegradation of reference substance achieved 78% within 14 days, meeting test criteria of achieving 60% within 14 days.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The biodegradation of test substance was 25.5% after 28 days, means the test substance is not ready biodegradable.

Description of key information

The biodegradation of test substance was 25.5% after 28 days, means the test substance is not ready biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater