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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:
17 January 2017 - 14 February 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Remarks:
photometrical analysis
Details on sampling:
Mean nitrate concentration [mg NO3/kg soil dry weight] in soil of the different treatments were analysed on the starting (day 0) and at the end of the test (day 28).
Vehicle:
no
Details on preparation and application of test substrate:
The test item was almost insoluble in water and organic solvents such as acetone or ethanol; therefore, the test item was ground with fine quartz sand using a pestle and mortar prior to being mixed together with the sand into the test soil.
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Remarks:
Supplier of soil: Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Obere Langgasse 40, D-67346 Speyer, Germany.
Test temperature:
18.3 - 21.1°C
Moisture:
± 5% of 45% of the maximum water-holding capacity (WHCmax).
Details on test conditions:
Physical and chemical properties of the test system:
Batch number: SP2.34316
Organic carbon [%]: 0.67 ± 0.03
Nitrogen [%]: 0.08 ± 0.01pH (0.01 M CaCl2): 5.9 ± 0.6
Cation exchange capacity [meq/100 g]: 7.6 ± 0.8
Particle size according to USDA [mm]: Relative distribution [%]
< 0.002 (clay) 6.8 ± 1.6
0.002 - 0.05 (silt) 33.6 ± 0.5
0.05 - 2.0 (sand) 59.6 ± 1.4
Soil type (USDA): sandy loam
Max. water holding capacity (WHCmax) [g/100 g]: 35.6 ± 1.4
Initial soil moisture [% dry mass]: 4.2 (*)
Soil moisture adjusted for test [% dry mass]: 16, equivalent to 45% of WHCmax
Microbial Biomass Carbon (Cmic) [μg Cmic g-1 soil]: 126
Cmic [% of Corg]: 1.89
Nominal and measured concentrations:
25.6, 64.0, 160, 400 and 1000 mg/kg soil dry weight
Reference substance (positive control):
no
Duration:
28 d
Dose descriptor:
other: LOAEC
Remarks:
No adverse effects were observed.
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
28 d
Dose descriptor:
other: NOAEC
Remarks:
No adverse effects were observed.
Effect conc.:
>= 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate

The test item had no adverse effects on N-transformation in lucerne amended soil during 28 days at test item concentrations of up to and including 1000 mg/kg soil dry weight. Due to the lacking of adverse effects effective concentrations (ECX) could not be calculated. Consequently, ECX are considered to be higher than 1000 mg/kg soil dry weight which was the highest tested concentration. Accordingly, LOAEC and NOAEC are > and ≥ 1000 mg/kg soil dry weight, respectively.

Validity criteria fulfilled:
yes
Conclusions:
Di(benzothiazol-2 -yl) disulphide showed no adverse effect on soil micro-organisms. Therefore the LOAEC and NOAEC are determined to be > 1000 mg/kg soil dry weight and ≥ 1000 mg/kg soil dry weight, respectively.
Executive summary:

The effects on soil micro-organisms of the substance di(benzothiazol-2 -yl) disulphide were investigated according to the OECD guideline 216. The test item had no adverse effects on N-transformation in lucerne amended soil during 28 days at test item concentrations of up to and including 1000 mg/kg soil dry weight. Due to the lacking of adverse effects effective concentrations (ECX) could not be calculated,

Consequently, ECX are considered to be higher than 1000 mg/kg soil dry weight which was the highest tested concentration. Accordingly, LOAEC and NOAEC are > and ≥ 1000 mg/kg soil dry weight, respectively (ECT 2017)

In conclusion, di(benzothiazol-2 -yl) disulphide is not considered to have adverse effects on soil micro-organisms.

Description of key information

The effects on soil micro-organisms of the substance di(benzothiazol-2 -yl) disulphide were investigated according to the OECD guideline 216. The test item had no adverse effects on N-transformation in lucerne amended soil during 28 days at test item concentrations of up to and including 1000 mg/kg soil dry weight. Due to the lacking of adverse effects effective concentrations (ECX) could not be calculated,

Consequently, ECX are considered to be higher than 1000 mg/kg soil dry weight which was the highest tested concentration. Accordingly, LOAEC and NOAEC are > and ≥ 1000 mg/kg soil dry weight, respectively (ECT 2017).

In conclusion, di(benzothiazol-2 -yl) disulphide is not considered to have adverse effects on soil micro-organisms.

Key value for chemical safety assessment

Additional information