3-anilino-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione;famoxadone (ISO)

Phototransformation in soil

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in soil

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-3 (Photodegradation Studies on Soil)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Annex II Proposed Guideline 7.1.1.1.2

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance name: [4-Phenoxyphenyl-14C]DPX-JE874 ([POP-14C]DPX-JE874)
Lot #: 2675-268
Specific activity: 59.6 µCi/mg
Radiochemical purity: >91%

Substance name: [Phenylamino-14C]DPX-JE874 ([PA-14C]DPX-JE874)
Lot #: 3048-238
Specific activity: 58.5 µCi/mg
Radiochemical purity: >98%

Radiolabelling:

yes

Analytical monitoring:

yes

Analytical method:

gas chromatography

high-performance liquid chromatography

mass spectrometry

Details on soil:

[POP-14C]test substance:
Soil classification: Sandy Loam
pH: 6.9
% Sand: 64.0
% Silt: 24.0
% Clay: 12.0
% Organic matter: 1.4
CEC (meq/100 g): 9.9
Bulk density (lb/cu ft): 76
Field capacity (% soil moisture at 1/3 bar): 10.8

[PA-14C]test substance:
Soil classification: Sandy Loam
pH: 7.2
% Sand: 53.2
% Silt: 36.0
% Clay: 10.8
% Organic matter: 1.4
CEC (meq/100 g): 9.2
Bulk density (lb/cu ft): 83
Field capacity (% soil moisture at 1/3 bar): 12.3

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

225 - 229

Relative light intensity:

10 447 - 12 316

Duration:

15 d

Temp.:

24 °C

Initial conc. measured:

200 g/ha d.w.

Dark controls:

yes

DT50:

> 30 d

Test condition:

non-irradiated

Key result

DT50:

4.1 d

Test condition:

irradiated sample at 24°C

Remarks on result:

other: 11.5 days correlated to natural sunlight

Transformation products:

yes

Remarks:

JS940, KF015, H3310, MN468, and MN467

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the test substance degraded with a calculated average first-order half-life of 4.1 days (11.5 days correlated to natural sunlight) while under nonirradiated conditions the average half-life was greater than 30 days.

Executive summary:

The study was conducted following US EPA guideline 161-3. The study investigated the effect of simulated sunlight on the route and the rate of degradation of test substance on soil thin layers. Solutions of [4-phenoxyphenyl-14C]test substance or [phenylamino-14C]test substance were applied to thin layers of Speyer sandy loam soil at a rate equivalent to 200 g ai/ha. Soil samples of each label were continuously irradiated under xenon arc lamps inside a Suntest® exposure unit for a period of 15 days (approximately 360 exposure hours, equivalent to approximately 42 days of natural summer sunlight in Wilmington, Delaware U.S.A.). Soil samples, prepared in the same manner, were shielded from light to serve as dark controls. The temperature of the test samples was maintained at approximately 24°C throughout the study.

Degradation of the test substance on layers of soil irradiated with simulated sunlight was substantially faster than degradation of identical samples under non-irradiated conditions. Under the conditions of this study, the test substance degraded with a calculated average first-order half-life of 4.1 days (11.5 days correlated to natural sunlight) while under nonirradiated conditions the average half-life was greater than 30 days.

Substantial mineralization to 14CO2 occurred in both labels [POP (10%), PA (30%)] after 15 days of continuous irradiation. The major extractable degradation products were identified as JS940, KF015, H3310, MN468, and MN467. JS940, KF015, and H3310 each retain the phenoxyphenyl ring system. MN467 and MN468 are nitro analogs of the test substance and were found in irradiated and non-irradiated samples.

The substantial difference in degradation rate between the irradiated and non-irradiated samples indicates photolytic processes on soil surfaces could enhance the overall rate of degradation of test substance in the environment.

Description of key information

Study Type	Study Details	Value	Guideline	Reliability
Phototransformation in soil	Applied on thin layers of Speyer sandy loam soil	DT50 = 4.1 days	EPA 161-3	1

Key value for chemical safety assessment

Half-life in soil:

4.1 d