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Toxicity to soil microorganisms

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Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005-01-12 - 2005-05-20
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 217 (Soil Microorganisms: Carbon Transformation Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
Soil samples (100 g soil d.w.) are taken at intervals of 3 hours, 7, 14 and 28 days after application of the test item. Before the beginning of the test, the optimal glucose concentration was determined. Before the measurements, glucose (0.4 %) is added and mixed with the soil by means of a hand-stirrer. The prepared samples are placed in reaction flasks (500 mL).

The measurement of the oxygen consumption is carried out with a respirometer "BSB digi" (SELUTEC, Mossingen-Oschingen, Germany). The system records 360 02-consumption data in 24 hours.
Vehicle:
yes
Details on preparation and application of test substrate:
The test item was dissolved in water and the test solution was then mixed with the soil in the mixing machine. Water was added to the soil to achieve a moisture of 45 % of WHC.
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Test temperature:
20 °C ± 2 °C
Moisture:
Soil moisture: approximately 45 % of its maximum water holding capacity.
Organic carbon content (% dry weight):
1.46
Nitrogen content (% dry weight):
0.15
Nominal and measured concentrations:
0.27 mg/kg d.w.
1.33 mg/kg d.w.
Reference substance (positive control):
yes
Remarks:
Dinoterb
Key result
Duration:
28 d
Dose descriptor:
other: carbon transformation in soil
Effect conc.:
> 1 000 g/ha
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: carbon transformation
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
> 1.33 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: carbon transformation
Results with reference substance (positive control):
The toxic standard dinoterb caused a reduction of the O2-consumption of > 25 % at the tested concentrations after 28 days and thus demonstrated the sensitivity of the test system.
Validity criteria fulfilled:
yes
Conclusions:
Based on the results of this study P 101/04 caused no short-term and long-term effects (OECD 217) on the carbon transformation in the field soil tested up to a concentration of 1.33 mg a.s. per kg soil d.w., equivalent to a field application rate of 1000 g a.s./ha.
Executive summary:

The purpose of this study was to determine the effects of the test item on the activity of soil microflora with regard to carbon transformation in a laboratory test. The test was performed in accordance to the OECD guideline 217 (2000) by measuring the short-term substrate induced respiration. The method is based on the initial respiratory response of microbial populations to which a carbon and energy source has been added (substrate-induced respiration, SIR).

This assay is based on the determination of O2 consumption of soil samples after glucose-induced respiration in a closed system for at least 24 hours. Soil samples (100 g soil d.w.) are taken at intervals of 3 hours, 7, 14 and 28 days after application of the test item. Before the beginning of the test, the optimal glucose concentration was determined. Before the measurements, glucose (0.4 %) was added and mixed with the soil by means of a hand-stirrer. The prepared samples were placed in reaction flasks (500 mL). The measurement of the oxygen consumption was carried out with a respirometer "BSB digi" (SELUTEC, Mossingen-Oschingen, Germany).

No differences greater than 25 % to the control in O2 consumption were found for any test concentration of P 101/04 at any time interval in comparison to the respective control. The coefficients of variation during the experiment were within the demanded limit (control < 15%).

Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005-01-12 - 2005-05-20
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The GLP study was conducted according to an internationally accepted guideline. All study parameters are based on the specific guideline.
Qualifier:
according to guideline
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
Determination of the nitrogen transformation (NO3-nitrogen production) in soil enriched with lucerne meal (concentration in soil 0.5 %). Comparison of test item treated soil with a non-treated soil. 3 replicates per treatment and concentration. NH4-nitrogen, NO3- and N02-nitrogen were determined by using the Autoanalyzer II (BRAN+LUEBBE). Sampling scheme: 0. 7, 14 and 28 days after treatment.
Vehicle:
yes
Details on preparation and application of test substrate:
The test item was dissolved in water and the test solution was then mixed with the soil by means of a hand-stirrer. Water was added to the soil to achieve a moisture of 45 % of WHC. The incubation of the prepared soil was carried out in new plastic vessels (500 mL). The tops of the vessels used permitted an air exchange with negligible moisture leakage (< 1 % loss).
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Test temperature:
20 ± 2 °C
Moisture:
approximately 45 % of WHC
Nominal and measured concentrations:
0.27 mg/kg d.w.
1.33 mg/kg d.w.
Reference substance (positive control):
yes
Remarks:
Dinoterb
Key result
Duration:
28 d
Dose descriptor:
other: soil nitrogen transformation
Effect conc.:
> 1 000 g/ha
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
> 1.33 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Results with reference substance (positive control):
In a separate study (study code: R 05 10 35 Nl) the reference item dinoterb caused effects greater than 25 % on the nitrogen transformation in a field soil at the tested concentrations 28 days after application.

Days after application

Control

P101/04 0.27 mg/kg soild.w.

P101/04 1.33 mg/kg soild.w.

NO3-N [mg/kg soild.w.]

CV[%]

NO3-N [mg/kg soild.w.]

CV[%]

Deviation from control (%)

NO3-N [mg/kg soild.w.]

CV[%]

Deviation

from control

(%)

0

23.5

5.1

22.2

1.2

-5.7

21.9

6.3

-6.8

7

46.1

0.4

47.0

1.3

+2.0

47.0

3.6

+2.0

14

49.3

2.8

49.3

3.6

-0.1

48.4

1.6

-2.0

28

58.0

0.8

59.9

2.7

+3.2

57.9

2.1

-0.2

Validity criteria fulfilled:
yes
Conclusions:
Based on the results of this study P 101/04 caused no short term and long-term effects (OECD 216) on the soil nitrogen transformation in the field soil tested up to a concentration of 1.33 mg a.s. per kg soil dry weight, equivalent to a field application rate of 1000 g a.s./ha.
Executive summary:

The test was performed in accordance to the OECD guideline 216 (2000).

No differences greater than 25 % to the control in the nitrogen transformation were found for any concentration of P 101/04 in comparison to the respective control. The coefficients of variation during the experiment were within the demanded limit (control < 15%).

Based on the results of this study P 101/04 caused no short-term and long-term effects (OECD 216) on the soil nitrogen transformation in a field soil tested up to a concentration of 1.33 mg a.s. per kg soil dry weight, equivalent to a field application rate of 1000 g a.s. per ha.

Description of key information

In two  28 d studies  no effects were observed on soil micro organism at 1000 g/ha or 1.33 mg/kg soil dw.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
1.33 mg/kg soil dw

Additional information