2,6-dibromo-4-cyanophenyl octanoate

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:

01 Apr - 05 May, 2011

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)

Version / remarks:

2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

From Sächsisches Staatsministerium für Umwelt und Landwirtschaft

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

Since the water solubility was low, the test item was thoroughly mixed with quartz meal.
136.4 g of test substance was mixed into 5 g quartz meal and diluted by a factor of 250 or 50 depending on the concentration to be acheived.
Subsequently the obtained mixture was added and mixed with the soil by means of a hand stirrer. For an optimum distribution of the test item in the soil, the test item quartz meal mixture was applied at a ratio of about 10 g per kilogram soil dry weight.

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

18.6 - 21.1 °C

Moisture:

water content 17.38 to 18.0 g per 100 g soil dry weight ( equivalent to 46.75 to 48.42 % of the WHC)

Organic carbon content (% dry weight):

35.51

Nitrogen content (% dry weight):

0.49

Details on test conditions:

200 g soil dry weight (= one sub-sample) per test vessel was weighed. The soil was mixed with 0.5 % (i.e. 1.0 g/200 g soil d.w.) lucerne meal by means of a hand-stirrer (the C/N ratio of the lucerne meal was 15.6/1).
One additional soil sample (without lucerne meal) was used for determination of the initial NO3-N-content. The NO3-N content was 1.55 mg /100 g soil d.w.
Water was added to the soil to achieve a water content of approximately 45 % of WHC. The incubation of the prepared soil was carried out in wide mouth glass flasks (500 mL). The screw caps of the flasks used permitted an air exchange.
The water content of the soil in each test vessel was determined at test start (after application) and adjusted once a week to the required range of 40-50 % of WHC.
The nitrogen transformation was determined on day 0 (after approximately 3 hours) and at intervals of 7, 14 and 28 days after application.

Nominal and measured concentrations:

Nominal concentrations: 1.09 and 5.46 mg test item/kg dry weight soil.

Reference substance (positive control):

yes

Remarks:

Dinoterb

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

> 5.46 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

The test substance caused a temporary stimulation of the daily nitrate rate at the tested concentrations of 1.09 mg/kg and 5.46 mg/kg dry soil at time interval 7 - 14 days after application.
However, no adverse effects of test substance on nitrogen transformation in soil could be observed at both tested concentrations at the end of the test, 28 days after application (time interval 14 - 28). Only negligible differences to control of -7.7 % (test concentration 1.09 mg/kg dry soil) and -15.4 % (test concentration 5.46 mg/kg dry soil) were measured at the end of the 28 - day incubation period (time interval 14 - 28).
The results for the time interval 0-28 days could also be calculated.

Results with reference substance (positive control):

28 days after appliaction, the differences to control of + 42.0 % (test concentration 6.80 mg/kg dry soil), + 68.1 % (test concentration 16.0 mg/kg dry soil) and + 92.3 % (test concentration 27.0 mg/kg dry soil) were measured.

Please refer to "overall remark/ attached background material" field for result tables.

The coefficients of variation in the control (NO3-N) were maximum 8.0 % and thus fulfilled the acceptance criterion (≤ 15 %).

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the NOEC (28 d) for nitrogen formation rates was > 5.46 mg test item/kg dry soil.

Description of key information

The test material, applied at 1.09 and at 5.46 mg a.i./kg dws, had no negative influence on nitrogen transformation in soil.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

5.46 mg/kg soil dw

Additional information

A key study investigating the toxicity of test material to N-cycle of soil microorganisms was available (2011). This test was conducted according to OECD guideline No. 216. The test material was incubated in the soil for 28 days at two concentration rates of 1.09 and 5.46 mg a.i./kg dws. The results found in the treatment groups regarding nitrogen concentrations and carbon transformation rates did not show any impact of this substance on soil microorganisms after 28 days.