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Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
Dec 2009- Jan 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Sorafenib tosylate was used as an analogue.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
Deviations:
no
Principles of method if other than guideline:
Not relevant
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Vehicle:
no
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Moisture:
22.6%
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
250 other: mg a.i./kg
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate

Since the inhibition value is negative, no inhibitory effect of the test item on soil microflora concerning nitrate production on day 28 was found when compared to the control soil.

Validity criteria fulfilled:
yes
Conclusions:
The test substance shows no inhibitory effect on the nitrification of soil microflora. Owing the outcome of the test, no calculation of ECx values is
possible. The NOEC is 250 mg a.i./kg.
Executive summary:

The purpose of the study is the determination of effects on soil microflora activity of BAY 54 -9085. On day 0, all test samples (with and without lucerne meal) showed almost equal nitrate concentrations, ranging from 139.4 to 152.0 mg NO3-/kg dry soil for the samples with lucerne meal, and ranging from 162.3 to 188.1 mg NO3-/kg dry soil for the nitrification control (NC) samples (without lucerne meal). In the NC control samples (no test item, without lucerne meal), the nitrate concentration increased from an average of 172.7 mg NO3-/kg dry soil on day 0 to an average of 236.6 mg NO3-/kg dry soil on day 28. For the NC 250 samples (250 mg a.i./kg dry soil, without lucerne meal), the mean nitrate concentration increased from 167.0 mg/kg dry soil on day 0 to 294.6 mg/kg dry soil on day 28. After 28 days, the mean nitrate transformation rates in the NC samples were 2.3 and 4.6 mg NO3-/kg dry soil per day for the NC control and the NC 250 treatment, respectively. The % inhibition of the nitrification in the NC 250 treatment compared to the NC control was -99.9%. An apparent contribution (63.8 mg NO3-/kg dry soil) of the nitrogen from the test item in the nitrate formation was calculated in the NC samples without lucerne meal. The nitrate concentration in the control samples with lucerne meal increased from an average of 150.3 mg NO3-/kg dry soil on day 0 to an average of 360.7 mg NO3-/kg dry soil on day 28. For the 250 mg a.i./kg dry soil treatment with lucerne meal, the mean nitrate concentration increased from 140.6 mg/kg dry soil on day 0 to 424.4 mg/kg dry soil on day 28. After 28 days, the mean nitrate transformation rate in the control samples was 7.5 mg NO3-/kg dry soil per day. The mean nitrification rate for the 250 mg a.i./kg dry soil treatment, adjusted for the contribution of the test item, was 7.9 mg NO3-/kg dry soil per day, equivalent to an inhibition of the nitrification compared to the control of -4.6%. Since the inhibition value is negative, no inhibitory effect of the test item on soil microflora concerning nitrate production on day 28 was found when compared to the control soil.

Description of key information

A guideline study according to OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test) was performed under GLP to assess the toxicity of BAY 54-9085 to soil microorganisms. Soil samples (with and without lucerne meal) were exposed to the test substance at a concentration of 250 mg a.i./kg dry soil. A control treatment without test substance was also prepared. Since the inhibition value is negative, no inhibitory effect of the test item on soil microflora concerning nitrate production on day 28 was found when compared to the control soil. The NOEC is 250 mg a.i./kg.

Key value for chemical safety assessment

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

Additional information