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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:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 217 (Soil Microorganisms: Carbon Transformation Test)
Deviations:
no
GLP compliance:
yes
Vehicle:
yes
Remarks:
Deionized water
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Test temperature:
18 to 22°C
Moisture:
20.0% w/w, equivalent to 50% of maximum water holding capacity
Nominal and measured concentrations:
Nominal: 0.133 and 1.3 mg/kg soil dry weight
Reference substance (positive control):
yes
Remarks:
Sodium chloride
Key result
Duration:
28 d
Remarks on result:
other: The test substance at a concentrations of 1.3 mg/kg soil dry weight (corresponding to 20-times the maximum application rate) have no long-term influence on nitrogen and carbon transformation in soils.
Validity criteria fulfilled:
yes
Conclusions:
The test substance at a concentrations of 0.133 and 1.3 mg/kg soil dry weight have no long-term influence on nitrogen and carbon transformation in soils.
Executive summary:

The study was conducted according to guidelines, OECD Guideline 216 and OECD Guideline 217 to evaluate the effect of test substance on soil microflora and to measure nitrogen transformation and short-term respiration following an application of the test item to loamy sand soil.

The test item was incubated in loamy sand soil over a period of 28 days for carbon transformation and nitrogen transformation at concentrations of 0.133 and 1.3 mg/kg soil dry weight. The concentrations tested were equivalent to 2- and 20-times maximum recommended single application rate of 25 g a.s./ha.

After 28 days, deviations in nitrate levels, nitrate formation rates and short-term respiration in soil treated with up to and including 1.3 mg/kg soil dry weight were less than 25% at the test end when compared to control indicating that no long term influence of the carbon and nitrogen transformation occurred in the soil.

The results showed that the difference in nitrate content between the two treatment groups (i.e., greater than and equal to the maximum predicted concentration in soil) and control was less than 25% at day 28, therefore the test item was evaluated as having no long-term influence on nitrogen transformation in soils.

The short-term respiration rate in soil treated with 0.133 and 1.3 mg/kg soil dry weight was statistically significantly different from the control at the end of the study (Day 28). At the end of the 28-day study, the respiration rate deviated 15.6% and 21.4% when compared to the control for the test concentrations of 0.133 and 1.3 mg/kg soil dry weight, respectively.

The difference in respiration rate between the two treatment groups (i.e., greater than and equal to the maximum predicted concentration) and control was less than 25% at sampling time after day 28, therefore the test item was evaluated as having no long-term influence on carbon transformation in soils.

These results conclude that the test substance had no long term influence on soil microbial nitrification or short-term respiration at concentrations up to and including 1.3 mg/kg soil dry weight after 28 days (deviations between treatments and controls for both nitrogen transformation and soil respiration were less than 25%, the effect threshold specified by the OECD guidelines). The highest test concentration of test item was based on twenty-times the recommended single maximum field application rate. The results indicate that there is a large margin of safety for test subsatnce for microbial processes in soil.

Description of key information

The test substance at a concentrations of 0.133 and 1.3 mg/kg soil dry weight have no long-term influence on nitrogen and carbon transformation in soils; OECD 216, 217; Reliability = 1

Key value for chemical safety assessment

Additional information