pymetrozine (ISO); (E)-4,5-dihydro-6-methyl-4-(3-pyridylmethyleneamino)-1,2,4-triazin-3(2H)-one

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 Nov 1994 to 21 Dec 1994

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)

Version / remarks:

July 1992

Deviations:

yes

Remarks:

Only one CO2 scrubber used

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge collected from the sewage treatment plant
- Collection date: 21/11/1994
- pH at collection: 7.6
- Preparation of inoculum for exposure: According to guideline. Before application, the inoculum was pre acclimated to the test medium overnight.

Duration of test (contact time):

29 d

Initial conc.:

28.3 mg/L

Based on:

test mat.

Remarks:

replicate 1, corresponding to 15.6 mg ThOC/L

Initial conc.:

27.4 mg/L

Based on:

test mat.

Remarks:

replicate 2, corresponding to 15.1 mg ThOC/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Reconstituted water: The test medium was prepared according to the method described in the guideline.
- Temperature: 22 ± 2 °C
- Aeration: Ca. 25 mL/min purified from carbon dioxide.

DESIGN
- Preparation of the mixtures: Before application, the inoculum was pre acclimated to the test medium over night. The aeration was performed inside 1.2 L water, containing the amount of mineral salts for 1.5 L. The final volume was made up to 1.5 L with a 300 mL mixture made from: the test substance (the above mentioned amount) in bidistilled water. This mixture was homogenized by ultrasonification for 1 minute and added to the test vessel, which was immediately connected to the CO2 scrubber.
- Vessels: 2 L dark brown glass flasks equipped with gas inlet and a magnetic stirrer.
- CO2 scrubbers: Approx 250 mL scrubbers with gas inlet tubes equipped with sintered glass tips containing 200 mL 0.05 N sodium hydroxide. Only one CO2 scrubber was used per test bottle. Theoretically, a solution of 0.05 M NaOH is sufficient to trap at least two times more CO2 than the maximum ThCO2 which can evolve in each test bottle (including CO2 possibly evolved from the bacteria e.g., endogenous respiration). Moreover, experimentally it was confirmed that no measurable CO2 carry over has ever occurred with the scrubbers used.

PREPARATIONS
The following test assays were prepared:
- 2 test substance treatment flasks (test substance and inoculum)
- 2 inoculum blank flasks
- 2 reference substance control flasks (procedure control)
- 1 toxicity control flask (reference substance, test substance and inoculum)

For the toxicity control, where the test substance and reference were applied together, the reference amount was 15.0 mg DOC/L and the test substance amount was 15.2 mg ThOC/L.

Reference substance:

benzoic acid, sodium salt

Remarks:

15 mg DOC/L

Preliminary study:

Not reported

Test performance:

Not reported

Key result

Parameter:

% degradation (CO2 evolution)

Value:

2

Sampling time:

29 d

Details on results:

Minor biodegradation was observed. Within the test substance treatments, CO2 evolution slowly increased over time, reaching an average of 12.7 mg C after 29 days, corresponding to a 2% biodegradation of the test substance. A detailed overview of the test results of the test substance and the controls is provided in 'Any other information on results incl. tables'.

Results with reference substance:

The degree of biodegradation of the reference substance after 20 days was 85% CO2/ThCO2. The degree of biodegradation of the reference substance with the test substance after 20 days was 86% CO2/ThCO2.

Table: CO2 evolution and biodegradation of the controls

CO2 evolution measured as mg C								Biodegradation
Day	Blank 1 [mg]	Blank 2 [mg]	Blank mean [mg]	Ref 1 [mg]	Ref 2 [mg]	Ref mean [mg]	Ref + TS [mg]	Ref [%]	Ref + TS [%]*
0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0	0
3	4.6	3.8	4.2	15.3	15.5	15.4	16.4	50	54
6	7.4	6.3	6.9	22.3	22.8	22.5	23.8	70	75
10	9.3	8.2	8.7	25.8	27.5	26.6	27.9	80	85
13	10.0	9.0	9.5	28.0	28.7	28.4	28.7	84	86
17	11.0	10.0	10.5	29.0	31.1	30.0	30.6	87	89
20	11.7	10.8	11.2	29.8	31.0	30.4	30.7	85	86
24	12.3	11.6	12.0	30.8	32.9	31.9	32.7	88	92
28	12.6	11.8	12.2	31.3	34.0	32.6	33.4	91	94
29	12.8	11.9	12.3	32.1	34.9	33.5	33.5	94	94

Ref = Reference substance

TS = Test substance

* The biodegradation of the "reference+ test substance" control is calculated with the applied

amount of the reference alone, i.e., 15 mg DOC/L.

 

Table: CO2 evolution and biodegradation of the test substance

Day	CO2 evolution measured as mg C		Biodegradation % of the test substance
	Replicate 1	Replicate 2	Replicate 1	Replicate 2	Mean
0	0.0	0.0	0	0	0
3	4.3	3.8	0	-2	-1
6	7.3	6.6	2	-1	0
10	9.5	8.4	3	-1	1
13	10.3	9.3	4	-1	1
17	11.6	10.6	4	0	2
20	12.3	11.3	5	0	2
24	13.0	12.0	4	0	2
28	12.7	11.9	2	-1	0
29	13.2	12.2	4	0	2

Negative degradation values as obtained in this test are a consequence of the comparison of

values obtained in the blank (endogenous respiration leading to a carbon dioxide evolution) and the low values obtained in the presence of the test substance.

Validity criteria fulfilled:

not specified

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance is not readily biodegradable in this test. The biodegradation calculated as percentage of measured amount of inorganic carbon over the theory was 2%.

Executive summary:

The biodegradation potential of the substance in water was determined in a screening study according to OECD TG 301B (CO2 -Evolution Test) and in compliance with GLP criteria. In this study, 15.6 and 15.1 mg/L TOC nominal (equivalent to 28.3 and 27.4 mg/L test substance) were inoculated with activated sludge from a sewage treatment plant for 29 days under aerobic conditions. During the incubation period the produced carbon dioxide (CO2) was measured and at the end of the test compared with the maximal theoretical CO2 production (ThCO2). Biodegradation was expressed as percentage of the measured CO2 (corrected for the blanc inoculum control) relative to the ThCO2. After the 29-day incubation period 2% of the substance was biodegraded. Based on these findings, the test substance is classified as not readily biodegradable.

Description of key information

Not readily biodegradable, OECD 301B (CO2-Evolution test), OECD 301B, Grade 1995

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater