Benzene, mono-C10-13-alkyl derivs., distn. residues

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Oct. 20, 2017-Feb. 26, 2018

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)

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

yes

Remarks:

Acetone

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: alfalfa


APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: A stock solution of the test substance in acetone was made. This was then mixed with 10.0001 g quartz sand, which was then added in appropriate amounts to the test soil.

VEHICLE:
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): acetone
- Concentration of vehicle in test medium (stock solution and final test solution): 5 g test substance/50 mL acetone
- Evaporation of vehicle before use: yes

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

18.96-21.79 degrees C

Moisture:

16.8-20.4% (43.5-52.8% maximum water holding capacity)

Details on test conditions:

TEST SYSTEM
- Testing facility: Laboratory
- Test container (type, material, size): 8 ounce French-square glass bottles with aluminum foil lids
- Amount of soil: 100 g dry soil (114 g moist soil)
- No. of replicates per concentration: 3
- No. of replicates per control: 3

SOIL INCUBATION
- Method: bulk

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): 38 degrees 42'35" N, 75 degrees 59'6" W
- History of site: Not farmed for 5 years, and 20 m from farmland. No recent drought or heavy rainfall
- Vegetation cover: grass and board leaf weeds
- Treatments with pesticides or fertilizers: None in past five years.
- Accidental contamination: no
- Depth of sampling: 0-10 cm
- Soil texture
- % sand: 74.2%
- % silt: 20.1%
- % clay: 5.7%
- Soil taxonomic classification: Sandy loam
- Soil classification system: USDA
- pH (in water): 6.5
- Initial nitrate concentration for nitrogen transformation test (mg nitrate/kg dry weight): 41.35 mg/L
- Maximum water holding capacity (in % dry weigth): 38.6%
- Cation exchange capacity (mmol/kg): 5.9 meq/100 g
- Pretreatment of soil: Sieved through a 2 mm screen. Water was added to the soil to 50% of the maximum holding capacity. 0.5 g of dried ground alfalfa was added. 1 g of quartz sand was added to the control replicates, and 1 g of quartz sand treated with test substance was added to the test replicates.
- Storage (condition, duration): 5 degrees C
- Initial microbial biomass as % of total organic C: 247.2 ug/g

DETAILS OF PREINCUBATION OF SOIL (if any): Soil was incubated at 20 degrees C for five days prior to test substance application.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Nitrate concentration was measured on Day 0 and Day 28. Nitrate concentrations were determined by HPLC analysis.

Nominal and measured concentrations:

0, 1000 mg/kg (nominal)

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

The mean nitrate concentration for the control replicates was 273.8 mg NO3/kg on Day 0, and 712.8 mg NO3/kg on Day 28. The mean nitrate concentration for the test replicates was 265.1 mg NO3/kg on Day 0, and 718.1 mg NO3 mg/kg on Day 28.

Reported statistics and error estimates:

See table below.

	Control	1000 mg/kg Test Substance
Mean Nitrate Concentration in Soil – Day 0 (mg/kg (RSD))	273.8 (1.5%)	265.1 (5.7%)
Mean Nitrate Concentration in Soil – Day 28 (mg/kg (RSD))	712.8 (2.5%)	718.1 (4.3%)
Mean Nitrate Formation in Soil  (mg NO3/kg day (RSD))	15.68 (3.8%)	16.18 (4.5%)
Nitrate Formation Inhibition	--	-3.21%

 

Validity criteria fulfilled:

yes

Conclusions:

The EC50 for Benzene, mono-C10-13-alkyl derivs., distn. residues based on inhibition of nitrate formation was >1000 mg/kg dry soil while the NOEC was >= 1000 mg/kg dry soil.

Executive summary:

The toxicity of Benzene, mono-C10-13-alkyl derivs., distn. residues to microorganisms was tested in an OECD Guideline 216 test. The test substance was added to soil at a concentration of 1000 mg/kg dry soil, and the nitrate formation determined after 28 days exposure. A negative control was also performed. The amount of nitrate formation was inhibited -3.21% in the test replicates as compared to controls. The EC50 based on inhibition of nitrate formation was >1000 mg/kg dry soil.  The NOEC was >= 1000 mg/kg dry soil.

Description of key information

The EC50 for Benzene, mono-C10-13-alkyl derivs., distn. residues based on inhibition of nitrate formation was >1000 mg/kg dry soil while the NOEC was >= 1000 mg/kg dry soil.

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:

1 000 mg/kg soil dw

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw