5,7-dichloro-4-(4-fluorophenoxy)quinoline;quinoxyfen (ISO)

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The key study available was conducted using a formulation which does not contain any other active ingredients and since the endpoints are expressed based on quinoxyfen, the studies are considered to represent the worst-case exposure, since a formulation ensures the exposure to the active ingredient (quinoxyfen) is maximised. The results are presented based on mg quinoxyfen/kg dw.

Qualifier:

according to guideline

Guideline:

BBA Part VI, 1-1

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Substance ID: EF 1186
- Name of substance: XDE-795 SC
- Batch: B0316A
EF-1186 is a formulation containing ~40% quinoxfen

Analytical monitoring:

no

Vehicle:

yes

Remarks:

distilled water

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: Loamy sand and silty loamy sand

APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: Target application concentrations achieved by diluting 0.1 mL (field rate) or 1.0 mL (10 times field rate) of test substance to 1000 mL in distilled water. 10.6 mL of each dilution distributed per kg soil (dry weight). This was equivalent to 0.53 a.i. mg/kg and 5.3 a.i. mg/kg

VEHICLE:
- Chemical name of vehicle: Distilled water

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

22 ± 2°C

Moisture:

ca. 45% soil moisture holding capacity

Details on test conditions:

TEST SYSTEM
- Testing facility: Euro Laboratories Limited
- Amount of soil: 1 Kg
- No. of replicates per concentration: 1
- No. of replicates per vehicle control: 1

SOIL INCUBATION
- Method: Series of individual subsamples

SOURCE AND PROPERTIES OF SUBSTRATE
- Soil texture: Loamy sand and Silty loamy sand

LOAMY SAND
- % fine sand (0.063-0.2 mm): 15.6
- % medium sand (0.2-0.63 mm): 31.9
- % coarse sand (0.63-2.0 mm): 11.9
- % fine silt (0.002-0.006 mm): 2.6
- % medium silt (0.006-0.02 mm): 8.6
- % coarse silt (0.02-0.06 mm): 20.7
- % clay (<0.002 mm): 8.6
- pH (in water): 5.7
- Maximum water holing capacity (%): 27.39
- Organic matter (%): 1.7

SILTY LOAMY SAND
- % fine sand (0.063-0.2 mm): 19.8
- % medium sand (0.2-0.63 mm): 16.4
- % coarse sand (0.63-2.0 mm): 4.2
- % fine silt (0.002-0.006 mm): 4.6
- % medium silt (0.006-0.02 mm): 11.6
- % coarse silt (0.02-0.06 mm): 30.7
- % clay (<0.002 mm): 12.6
- pH (in water): 7.4
- Maximum water holing capacity (%): 42.80
- Organic matter (%): 5.0

DETAILS OF PREINCUBATION OF SOIL: The soils were sieved to pass a 2 mm screen and stored at 4-10°C prior to conditioning at test temperature of 22 ± 2°C for 7 days.

EFFECT PARAMETERS MEASURED: Microbial respiration and soil nitrogen turnover at Days 0, 14, and 28

VEHICLE CONTROL PERFORMED: Yes

Nominal and measured concentrations:

0.53 mg/kg soil (equivalent to a field application rate of 0.8 litres per ha) and 5.3 mg/kg (equivalent to 10 times field application rate)

Reference substance (positive control):

yes

Remarks:

Aretit Flussig (dinoseb acetate, 49.2% w/v)

Key result

Duration:

28 d

Basis for effect:

respiration rate

Remarks on result:

other: The test substance had no significant effect on microbial respiration in either the loamy sand soil or the silty loamy sand soil

Key result

Duration:

28 d

Basis for effect:

nitrate formation rate

Remarks on result:

other: The test substance had no statistically significant effect on nitrogen turnover in the loamy sand and the silty loamy sand soils when applied at either 0.53 or 5.3 mg a.s./kg

Results with reference substance (positive control):

Soil microflora respiration and nitrogen turnover: The reference substance produced a statistically significant effect in both the soils.

Validity criteria fulfilled:

yes

Conclusions:

The test substance would not be expected to cause any effects on the turnover of carbon and nitrogen in soil

Executive summary:

The influence of the test substance on soil microflora was determined using short term respiration experiments and by monitoring nitrogen turnover in accordance with BBA guidelines VI 1-1.

A suspension of the test substance in water was applied to a loamy sand and a silty loamy sand soil at a concentration of 0.53 mg/kg soil (equivalent to a field application rate of 0.8 litres per ha) and 5.3 mg/kg (equivalent to 10 times field application rate). The treated soils were incubated at a temperature of 22 ± 2°C and at ca 45% soil moisture holding capacity for 28 days.

The effect of the test substance on microbial respiration was investigated using short term respiration experiments conducted within 3 hours of treatment and after 14 and 28 days. On each occasion, aliquots of soil were amended with a non-limiting quantity of glucose and carbon dioxide evolution measured over the subsequent 24-hour period using an infra-red gas analyzer. Values for substrate induced respiration rate were converted to soil microbial respiration (ml CO2 per h 100 g per soil) for data presentation.

The effects on nitrogen turnover were investigated by determining ammonium-N, nitrate-N and nitrite-N concentrations in soil amended with ground lucerne grass. Aliquots of soil were extracted with 2M KCl within 3 hours of treatment and after 14 and 28 days. The concentrations of mineral nitrogen species in extracts were determined colorimetrically.

Test substance when applied at either the field rate or 10 times the field rate, had no statistically significant effect (at p = 0.05 level) on microbial respiration in either the loamy sand soil or the silty loamy sand soil.

The test substance had no statistically significant effect (p = 0.05 level) on nitrogen turnover in the loamy sand and the silty loamy sand soils when applied at either the field rate or 10 times the field rate. The concentrations of all mineral-N species in both soil types treated at either the field rate or 10 times the field rate were within 15% of those in the control soils.

At the maximum concentration tested, 5.3 mg a.i./kg dw, there was less than 15 % effect on nitrogen transformation (not statistically significant from the control) and no effects on the carbon transformation.

Description of key information

28-day NOEC (C and N transformation) = 5.3 mg quinoxyfen/kg dw exposed as a formulation (EF-1186)

The test substance would not be expected to cause any effects on the turnover of carbon and nitrogen in soil; BBA Part VI, 1-1; Reliability = 1