Desmedipham

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:

2011-09-13 to 2011-11-07

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:

no

Vehicle:

no

Details on preparation and application of test substrate:

- Controls: The control was prepared with quartz meal only
- Other information: As stated in OECD Guideline 216, an agriculturally utilised soil was selected. The soil was removed to a depth of 20 cm as mixed sample. Afterwards, the soil was carefully dried at room temperature, passed through a 2 mm mesh sieve and then stored at a temperature of approx. 4°C in containers under aerobic conditions in the dark. Before application, the soil was adapted to test conditions. The test item was applied as requested at an application rate of 0.48 kg/ha and a tenfold application rate of 4.8 kg/ha

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Remarks:

A loamy sand soil was exposed for 28 days.

Test temperature:

18.9 - 20.9°C in a climatic room

Moisture:

16.95 - 17.47 g/100 g soil d.w. (equivalent to 46.21 - 47.64% of WHC)

Organic carbon content (% dry weight):

1.39

Nitrogen content (% dry weight):

0.13

Details on test conditions:

SOURCE AND PROPERTIES OF SUBSTRATE
- Geographic location: Wassergut Canitz, Germany
- Sampling depth (cm): 20 cm
- % sand: 53.0 (USDA); 51.7 (DIN 11277)
- % silt: 36.8(USDA); 38.1 (DIN 11277)
- % clay: 10.2 (USDA and DIN 11277)
- Soil classification system: sandy loam or loamy sand
- Organic carbon (%): 1.39
- Maximum water holding capacity (in % dry weigth): 36.67 (g/100 g soil d.w.)
- CEC: 10.0 (cmol+ /kg soil)

OTHER TEST CONDITIONS
- Photoperiod: darkness

Nominal and measured concentrations:

Nominal concentration: 0.64 and 6.40 mg test item/kg soil dw

Reference substance (positive control):

yes

Remarks:

dinoterb

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 6.4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: no adverse effects (difference to control < 25%, OECD 216) on the soil nitrogen transformation

Details on results:

At time interval 7-14 days after application, Desmedipham a.s caused a temporary inhibition of the daily nitrate rate at the tested concentration of 0.64 mg/kg dry soil. However, no adverse effects of Desmedipham a.s on nitrogen transformation in soil could be observed at the test concentration of 0.64 mg/kg dry soil, 28 days after application. Only negligible differences to control of +10.6% (test concentration 0.64 mg/kg dry soil) and -12.3% (test concentration 6.40 mg/kg dry soil) were measured at the end of the 28-day incubation period. (time interval 14-28). The coefficients of variation during the experiment were within the demanded limit (control =15%)

Results with reference substance (positive control):

In ae most recent test, the toxic standard dinoterb caused an effect of +42.0%, +68.1% and +92.3% (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 and thus demonstrates the sensitivity of the test system

See "Attachments" in "Overall remarks, attachments" for the tables and appendixes;

Validity criteria fulfilled:

yes

Remarks:

The coefficients of variation in the control (NO3-N) were maximum 5.6% and thus fulfilled the demanded range (=15%).

Conclusions:

The coefficients of variation in the control (NO3-N) were maximum 5.6% and thus fulfilled the demanded range (=15%). Also, the water content of the soil (46-48% of MWHC) was within the range recommended in the guideline (40-60%, but within a range of 5%). Dinoterb was tested as reference item in a separate study even though a reference item is not required by the OECD guideline 216. The results with the reference item verified the sensitivity of the test system. The difference between the effect of desmedipham on the soil nitrogen transformation (measured as NO3-N rate) to control was <25% at the end of the 28-day incubation period. The study was performed in a field soil at concentrations up to 6.4 mg a.s./kg soil dry weight, which is equivalent up to an application rate of 4.8 kg a.s./ha.

Executive summary:

Desmedipham a.s. caused no adverse effects (difference to control <25%, OECD 216) on the soil nitrogen transformation (measured as NO₃-N production) at the end of the 28-day incubation period. The NOEC was determined to be ≥6.40 mg a.s./kg soil dw.

Description of key information

The purpose of this study was to determine the effects of Desmedipham on the activity of soil microflora with regard to nitrogen transformation in a laboratory test. A loamy sand soil was exposed for 28 days to 0.64 and 6.40 mg/kg soil dw.¿Desmedipham caused no adverse effects. At the end of the 28-day incubation period of the soil nitrogen transformation (measured as NO₃-N production) a non-statistical difference in the NO₃-N production in the treatment of -12.3% compared to the control was observed (validity criterium: difference to control <25%).  The NOEC was determined to be ≥6.4 mg/kg soil dw. 

 

In the table below all available studies are listed. For some studies only the results are presented since they are not considered relevant due to the reasons given under “Assessment”. All available studies have been evaluated within the scope of Plant Protection Regulation in the respective Draft Renewal Assessment Report (DAR) under Regulation (EC) 1107/2009.

Test species	Result	Assessment	Reference
Soil microorganisms (loamy soil)	28-d NOEC ≥6.4 mg/kg dws	Key study	Schulz (2011)
Soil microorganisms (loamy soil)	Desmedipham does not significantly affect the populations of bacteria, fungi, or actinomycetes in soil treated with 1, 5 and 25 ppm of the compound.	Study is not considered valid as no replicates were included, and no statistical evaluation was performed between controls and treatments. Also, it is a non-GLP study.	Ercegovich & Bogus (1974)

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

6.4 mg/kg soil dw