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

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Jul 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: 87/302/EEC (page 118-122): Acitivated sludge respiration inhibition test

Deviations:

yes

Remarks:

see 'Any other information on materials and methods incl. tables'

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

- Preparation: 20.27, 8.23, 3.20, 1.33, 0.53 and 0.26 mg of the test substance were weighed and added to the test medium. The volume was adjusted to 200 mL with water and aerated for 3 hours.

Test organisms (species):

activated sludge

Details on inoculum:

- Source: Activated sludge was collected from the sewage treatment plant.
- pH after collection: 7.1
- Preparation of inoculum for exposure

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 ± 2 °C

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 1.3, 2.7, 6.7, 16.0, 41.2 and 101.4 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL BOD flasks with gas inlet
- No. of vessels per concentration: 1
- No. of vessels per control: 2
- No. of vessels per reference control: 1 per concentration
- Sludge concentration: 1.59 g/L (dry weight)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dechlorinated drinking water
- Nutrient solution: 16g peptone, 11g meat extract, 3.0 g urea, 0.7 g NaCl, 0.4 g CaCl2.7H2O, 0.2 g MgSO4.7H2O and 2.8 g K2HPO4 dissolved and made up to one liter with dechlorinated drinking water

EFFECT PARAMETERS MEASURED: oxygen consumption
Oxygen consumption per hour was measured in mg/L with an ORION - Electrode Type 97-08, ORION Microprocessor Ionalizer 901 and plotted on a recorder. The inhibitions were calculated on the basis of the measured time-depent oxygen consumption of a blank and test solution.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (3.2, 10.0 and 32.1 mg/L)

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: NOEC value not presented in the study report; derived by the registrant

Details on results:

No inhibition in oxygen consumption was observed in all test substance treatments compared to the blank control.

Results with reference substance (positive control):

The 3-h EC50 of the reference substance was determined to be 13.3 mg/L.

Table: Results

Sample	Conc. [mg/L]	Consumption rate [mg/L/h]	Inhibition [%]	pH
Blank 1	0.0	58.1	-3	8.1
Blank 2	0.0	54.4	3	8.1
Reference 1	32.1	12.8	77	8.2
Reference 2	10.0	31.9	43	8.2
Reference 3	3.2	54.6	3	8.1
Test conc. 1	101.4	61.2	-9	8.0
Test conc. 2	41.2	57.7	-3	8.0
Test conc. 3	16.0	58.9	-5	8.0
Test conc. 4	6.7	57.9	-3	8.0
Test conc. 5	2.7	58.8	-4	8.0
Test conc. 6	1.3	60.0	-7	8.0

Validity criteria fulfilled:

not specified

Conclusions:

The 3-h EC50 value is >100 mg/L for microorganisms present in activated sludge from a sewage treatment plant. The NOEC is determined to be 100 mg/L.

Executive summary:

The toxicity of the substance to microorganisms was investigated in an activated sludge respiration inhibition study according to 87/302/EEC (page 118-122) and in compliance with GLP criteria. In this study non-adapted activated sludge from a sewage was exposed to test substance concentrations of 0 (control), 1.3, 2.7, 6.7, 16.0, 41.2 and 101.4 mg/L. Nominal test concentrations were not analytically verified. The effects on microorganisms was determined by measuring total respiration rates and comparing these to an unexposed control. No inhibition in oxygen consumption was observed in all test substance treatments compared to the blank control. Based on these findings, a 3-h EC50 value of >100 mg/L was derived. Although no NOEC was derived in the study report, the absence of inhibition of respiration in the highest tested concentration of 100 mg/L justifies the NOEC to be determined at 100 mg/L.

Description of key information

The 3-h EC50 and NOEC are >100 and 100 mg/L, respectively, in microorganisms in STP sludge, 87/302/EEC, Baumann 1992

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

Table: Overview of available data on the toxicity to microorganisms

Species	Guideline / GLP	Endpoint	Effect value	Comment	Reference
Activated sludge from STP	87/302/EEC / GLP	3-h EC50 3-h EC20 3-h NOEC	> 100 mg/L > 100 mg/L 100 mg/L*	No inhibition in oxygen consumption was observed in all treatments	Baumann, 1992

*: highest tested concentration