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Ecotoxicological information

Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 09 December, 2015 to June, 2016
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)
Deviations:
yes
Remarks:
Temperature was lower than the range stated in the study plan for less than 2 hours. No appropriate determination of EC50 was possible. The NOEC was stated instead. The concentrations stated in the study plan deviate from the weighted concentrations.
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
The soil was divided into 6 portions of 900 g. The required amount of 4.2 g organic substrate was given to each portion and the soil samples were homogenised. To each portion the required amount of test item was added using 62.6 mL deionised water which was also used for adjustment of the soil moisture and then thoroughly mixed. Each portion was divided into 3 replicates of 300 g and incubated in glass jars.
The amount of organic substrate corresponded to the recommended value in the guideline (5 g substrate per 1000 g dry weight of used test soil).
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Test temperature:
17.8 - 21.3°C
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): glass preserving jars, 1L
- Amount of soil: 300 g
- No. of replicates per concentration: 3
- No. of replicates per control: 3

SOIL INCUBATION
- Method: series of individual subsamples

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Offenbach, Germany
- Vegetation cover: uncultivated
- Treatments with pesticides or fertilizers: no
- Accidental contamination: no
- Depth of sampling: 20 cm
- Soil texture
- % sand: 54.7 - 60.5%
- % silt: 32.7 - 39.1%
- % clay: 4.9 - 8.3%
- Soil taxonomic classification: LUFA Speyer
- Soil classificCaCl2): ca. 5.7
- Initial nitrate concentration for nitrogen transformation test (mg nitrate/kg dry weight):
- Maximum water holding capacity (in % dry weigth): 35.4 +/- 1.5%
- Cation exchange capacity (mmol/kg): 7.5 +/- 0.9 meq/100 g
- Initial microbial biomass as % of total organic C: 3.49 - 3.82 %

VEHICLE CONTROL PERFORMED: no
Nominal and measured concentrations:
0, 1000, 1800, 3200, 5600 and 10000 mg/kg soil dw
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
ca. 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Details on results:
- Nitrate production in % compared to controls:
1000 mg/kg soil dw: -1.6
1800 mg/kg soil dw: 17.8
3200 mg/kg soil dw: 72.9
5600 mg/kg soil dw: 54.9
10000 mg/kg soil dw: 69.8
Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the 28 d NOEC for the test substance was determined to be 1000 mg/kg soil dry weight (nominal) (Bangert, 2016).
Executive summary:

A study was conducted to determine the effects of the test substance, DPHA on nitrogen transformation in soil according to OECD Guideline 216 and EU Method C21, in compliance with GLP. The study was performed using the following 5 concentrations: 1000, 1800, 3200, 5600 and 10000 mg/kg soil dry weight. Sieved soil was exposed to the test item for 28 days. After 0 and 28 days, the nitrate content of the soil of each treatment was determined. A blank control was tested in parallel. The four highest concentrations showed inhibition of Nitrate production compared to the control. However, no appropriate determination of the EC50 was possible due to missing linearity of the dose response. Therefore, the NOEC was stated as 1000 mg/kg soil dry weight. Under the study conditions, the 28 d NOEC for the test substance was determined to be 1000 mg/kg soil dry weight (nominal) (Bangert, 2016).

Description of key information

Based on the study results, the 28 d NOEC for the test substance was determined to be 1000 mg/kg soil dry weight (nominal).

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
1 000 mg/kg soil dw

Additional information

A study was conducted to determine the effects of the test substance, DPHA on nitrogen transformation in soil according to OECD Guideline 216 and EU Method C21, in compliance with GLP. The study was performed using the following 5 concentrations: 1000, 1800, 3200, 5600 and 10000 mg/kg soil dry weight. Sieved soil was exposed to the test item for 28 days. After 0 and 28 days, the nitrate content of the soil of each treatment was determined. A blank control was tested in parallel. The four highest concentrations showed inhibition of Nitrate production compared to the control. However, no appropriate determination of the EC50 was possible due to missing linearity of the dose response. Therefore, the NOEC was stated as 1000 mg/kg soil dry weight. Under the study conditions, the 28 d NOEC for the test substance was determined to be 1000 mg/kg soil dry weight (nominal) (Bangert, 2016)