1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

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:

2015-02-13 to 2015-04-28

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:

January 21, 2000

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The test material is a white solid.

Analytical monitoring:

yes

Details on sampling:

A sample of each replicate of each treatment was taken at intervals of 3 hours, 7, 14, 28 and 42 days and the mineral nitrogen content of the soil was determined.

Vehicle:

no

Details on preparation and application of test substrate:

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 13.2/1, see Appendix 1). One additional soil sample (without lucerne meal) was used for determination of the initial NO3-N-content. The initial NO3-N-content was 4.45 mg /100 g soil d.w. Since the water solubility was very low, the test item was thoroughly mixed with quartz sand. 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 sand mixture was applied at a ratio of about 10 g per kilogram soil dry weight. Water was added to the soil to achieve a water content of approximately 45% of WHC (see Appendix 2). The incubation of the prepared soil was carried out in wide mouth glass flasks (500 mL) under the conditions mentioned above. 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 (see Appendix 4). The pH-values of the soil used in the test were measured at test start (after application) and at the sampling on day 28 and 42 (see Appendix 4).

Test organisms (inoculum):

other: sandy loam or loamy sand

Total exposure duration:

42 d

Test temperature:

19.2 - 20.7°C

Moisture:

18.21 - 19.54 g/100 g soil d.w. (equivalent to 46.04 - 49.42% of WHC)

Details on test conditions:

TEST SYSTEM
- Test container (type, material, size): glass flasks (500 mL)
- Amount of soil: 200 g soil dry weight (= one sub-sample) per test vessel.
- No. of replicates per concentration: 3 replicates
- No. of replicates per control: 3 replicates

SOIL INCUBATION
- Method: The incubation of the soil samples was performed as a series of individual and equally sized sub-samples of each treatment group.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): 12.694435960 degrees East, 51.403774567 degrees North
- Depth of sampling: 20 cm
- Soil texture
- % sand: 54.3 (USDA), 52.9 (DIN 11277)
- % silt: 35.1 (USDA), 36.6 (DIN 11277)
- % clay: 10.6 (USDA), 10.6 (DIN 11277)
- Soil classification system: sandy loam according to USDA or loamy sand according to DIN 11277.
- pH (in water): 6.1
- Maximum water holding capacity (in % dry weigth): 39.54 g/100 g soil d.w.
- Cation exchange capacity (mmol/kg): 11.2 cmol+ /kg soil

Nominal and measured concentrations:

Nominal concentration: 2 and 10 mg a.s./kg soil dry weight

Reference substance (positive control):

yes

Remarks:

Dinoterb

Key result

Duration:

42 d

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

Nitrogen transformation
The findings are summarised in the table below. Values are given as mg NO3-N/kg soil d.w. The test item pencycuron a.s. caused a temporary stimulation of the daily nitrate rate at the tested concentrations of 2 mg a.s./kg dry soil and 10 mg a.s./kg dry soil at time interval 14-28 days after application. However, no adverse effects of pencycuron a.s. on nitrogen transformation in soil could be observed at both tested concentrations at the end of the test, 42 days after application (time interval 28-42). Differences from the control of -0.4% (test concentration 2 mg a.s./kg dry soil) and -0.8 % (test concentration 10 mg a.s./kg dry soil) were measured at the end of the 42-day incubation period (time interval 28-42). For details see Table 2.

Results with reference substance (positive control):

In the most recent test with the toxic standard, Dinoterb caused an effect of +39.1%, +62.5% and +112.0% (required =25%) on the nitrogen transformation in a field soil at the tested concentrations of 6.80 mg, 16.00 mg and 27.00 mg Dinoterb per kg soil dry weight, respectively, 28 days after application (time interval 14-28) and thus demonstrates the sensitivity of the test system

Validity criteria fulfilled:

yes

Remarks:

The coefficients of variation in the control for NO3-N were maximum 7.8% and thus fulfilled the demanded range (=15%).

Conclusions:

Pencycuron a.s. caused no adverse effects (difference to control <25%, OECD 216) on the soil nitrogen transformation (expressed as NO3-N-production) at the end of the 42-day incubation period. The study was performed in a field soil at concentrations up to 10 mg a.s./kg dry soil weight.

Executive summary:

At the end of the 42-day incubation period, Pencycuron a.s. caused no adverse effects (difference to control <25%, OECD 216) on the soil nitrogen transformation (expressed as NO3-N-production). No effects (effects <25%) was observed at 10 mg a.s./kg dws after 42 days of incubation.

Description of key information

The purpose of this study was to determine the effects of Pencycuron on the activity of soil microflora with regard to nitrogen transformation in a laboratory test. A loamy sand soil was exposed for 42 days to 2.0 and 10.0 mg/kg soil dw. Pencycuron caused no adverse effects (difference to control <25%) on the soil nitrogen transformation (measured as NO₃-N production) at the end of the 42-day incubation period. The NOEC was determined to be ≥10.0 mg a.s./kg soil dw.

 

Test species	Result	Assessment	Reference
Sandy loam soil	42-d NOEC ≥10.0 mg a.s./kg soil dw	Key study	Schulz (2015)

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

10 mg/kg soil dw