Fenamiphos

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

Study period:

28 d

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

The test item is Fenamiphos CS 240

Analytical monitoring:

not required

Vehicle:

yes

Remarks:

The test item was dissolved in water.

Details on preparation and application of test substrate:

The following mixtures of soil, lucerne meal and distilled water, containing the test item for the test item groups, were prepared with three replicates, each:
Group 1 (control): 2 kg soil + lucerne meal + water
Group 2: 2 kg soil + lucerne meal + water containing the test item at a target concentration of 4 mg a.i./kg
Group 3: 2 kg soil + lucerne meal + water containing the test item at a target concentration of 20 mg a.i./kg

Lucerne meal was distributed over the surface of the test soil (thin layer of approximately 2.5 cm) and mixed thoroughly. Distilled water was then sprinkled onto the test soil to increase the soil moisture content to 50 % of the soil water holding capacity (WHC). For preparation of Group 2 and Group 3, the test item was mixed with this distilled water addition before sprinkling over the test soil.

For the target concentration of 4 mg a.i./kg (Group 2), 2.89 mL of diluted test item (diluted to 2.49 mg/mL) containing 7.20 mg fenamiphos was added to the distilled water to 2 kg wet soil for each replicate (equivalent to 4 mg fenamiphos/kg soil dry weight).
For the target concentration of 20 mg a.i./kg (group 3), 14.44 mL of diluted test item (diluted to 2.49 mg/mL) containing 35.96 mg fenamiphos was added to the distilled water to 2 kg wet soil for each replicate (equivalent to 20 mg fenamiphos/kg soil dry weight).

Following preparation, the soil groups were incubated in the dark in a temperature controlled room.

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

The soil groups were incubated in the dark in a temperature controlled room set at 20 °C ± 2 °C.

Moisture:

The moisture content of the soil groups was checked weekly by weight and the moisture adjusted by adding sufficient distilled water.

Organic carbon content (% dry weight):

1.2

Details on test conditions:

A sandy loam soil with 73 % sand, 16 % silt and 11 % clay and a pH of 6.8 was used. The maximum water holding capacity was 30.7 %. The soil microbial biomass was 2.61 %. The test soil was received at the test facility on 10 May 2007 and stored at approximately 4 °C and then transferred to 20 ± 2 °C for 7 days prior to testing.
Lucerne meal (sieved to 2 mm maximum) having a carbon:nitrogen ratio of 13.9:1 was used to amend the test soil with a suitable nitrogen source and 8.99 g was added to 2 kg test soil, having a dry weight of 1797 g, to give a final concentration of lucerne meal of 0.5 % on a soil dry weight basis.

Triplicate soil samples of each of the control and test item group were withdrawn within 6 hours of treatment on Day 0 and at 7, 14 and 28 days after preparation. The samples were either stored in a deep freeze (-20 °C) or extracted on the same day as sampling. The supernatant solutions were analysed on the same day or transferred to a deep-freeze at approximately -20 °C to await analysis. The soil samples were analysed for ammonium, nitrite and nitrate concentrations using a continuous flow colorimetric autoanalyser.

Nominal and measured concentrations:

Group 1: control
Group 2: 4 mg a.i./kg
Group 3: 20 mg a.i./kg

Key result

Duration:

28 d

Dose descriptor:

other: effect <25 %

Effect conc.:

20 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Duration:

14 d

Dose descriptor:

other: effect < 25 %

Effect conc.:

20 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Duration:

7 d

Dose descriptor:

other: effect < 25 %

Effect conc.:

20 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Duration:

28 d

Dose descriptor:

other: effect < 25 %

Effect conc.:

4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Duration:

14 d

Dose descriptor:

other: effect < 25 %

Effect conc.:

4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Duration:

7 d

Dose descriptor:

other: effect < 25 %

Effect conc.:

4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

 

Day	Nitrate as µg N/g soil dry weight			Deviation to control in %
	Group 1 (control)	Group 2 (4 mg a.i./kg)	Group 3 (20 mg a.i./kg)	Group 2 (4 mg a.i./kg)	Group 3 (20 mg a.i./kg)
0	3.87	3.97	4.23	+ 2.58	+ 9.30
7	13.91	14.83	18.96	+ 6.61	+ 36.30
14	39.85	37.05	39.97	- 7.03	+ 0.30
28	57.01	43.52	70.79	- 23.66	+ 24.17
Each value is a mean figure derived from three replicate analyses

 

Day	Ammonium as µg N/g soil dry weight			Deviation to control in %
	Group 1 (control)	Group 2 (4 mg a.i./kg)	Group 3 (20 mg a.i./kg)	Group 2 (4 mg a.i./kg)	Group 3 (20 mg a.i./kg)
0	4.89	5.05	5.49	+ 3.27	+ 12.27
7	15.73	16.27	25.69	+ 3.43	+ 63.32
14	6.49	6.27	10.34	- 3.39	+ 59.32
28	BLQ	BLQ	BLQ	-	-
Each value is a mean figure derived from three replicate analyses

Validity criteria fulfilled:

not specified

Conclusions:

The nitrogen transformation results from this study demonstrated that ammonium and nitrate concentrations in soil treated with 4 mg a.i./kg soil dry weight and 20 mg a.i./kg soil dry weight were comparable to those in the control soil over the study period. By Day 28, deviations in nitrogen transformation activity in soil treated with the test item compared to the control soil were less than 25 % for all parameters examined.

In conclusion, the test item can be evaluated as having no long-term influence on nitrogen transformation in soils.

Executive summary:

The test item was tested at two treatment concentrations: 4 mg a.i./kg soil dry weight and 20 mg a.i./kg soil dry weight. The test soil was a sandy loam soil.

To determine nitrogen transformation, a control soil (Group 1) and soils treated with the test item (Group 2 = 4 mg a.i./kg soil dry weight, Group 3 = 20 mg a.i./kg soil dry weight), were incubated in the dark at 20 ± 2 °C as three replicate bulk samples per treatment group. Each soil group was amended with lucerne meal, as a nitrogen source, at the time of preparation. Triplicate portions of each soil group replicate were sampled within 6 hours (Day 0), 7, 14 and 28 days after preparation and then extracted for analysis of ammonium, nitrite and nitrate concentrations using a continuous flow colorimetric autoanalyser.

The nitrogen transformation results from this study demonstrated that ammonium and nitrate concentrations in soil treated with the test item at 4 mg a.i./kg soil dry weight and 20 mg a.i./kg soil dry weight were comparable to those in the control soil over the study period. By Day 28, deviations in nitrogen transformation activity in soil treated with the test item compared to the control soil were less than 25 % for all parameters examined.

In conclusion, the test item can be evaluated as having no long-term influence on nitrogen transformation in soils.

Description of key information

The test item was tested at two treatment concentrations: 4 mg a.i./kg soil dry weight and 20 mg a.i./kg soil dry weight. The test soil was a sandy loam soil.

To determine nitrogen transformation, a control soil (Group 1) and soils treated with the test item (Group 2 = 4 mg a.i./kg soil dry weight, Group 3 = 20 mg a.i./kg soil dry weight), were incubated in the dark at 20 ± 2 °C as three replicate bulk samples per treatment group. Each soil group was amended with lucerne meal, as a nitrogen source, at the time of preparation. Triplicate portions of each soil group replicate were sampled within 6 hours (Day 0), 7, 14 and 28 days after preparation and then extracted for analysis of ammonium, nitrite and nitrate concentrations using a continuous flow colorimetric autoanalyser.

The nitrogen transformation results from this study demonstrated that ammonium and nitrate concentrations in soil treated with the test item at 4 mg a.i./kg soil dry weight and 20 mg a.i./kg soil dry weight were comparable to those in the control soil over the study period. By Day 28, deviations in nitrogen transformation activity in soil treated with the test item compared to the control soil were less than 25 % for all parameters examined.

In conclusion, the test item can be evaluated as having no long-term influence on nitrogen transformation in soils.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

20 mg/kg soil dw