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

Phototransformation in water

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Study type:

direct photolysis

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: USA: 40 CFR 158.290. Environmental Fate Data Requirements. Degradation Studies-lab. Photochemical degradation

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: European Union Commission Directive 94/37 EC amending Council Directive 91/414/EEC. Physical and Chemical Properties of the Active Substance. Points 2.9.2, 2.9.3 Photochemical degradation, Quantum yield

GLP compliance:

yes

Specific details on test material used for the study:

Substance name: [14C-Phenoxyphenyl]DPX-JE874; [14C-POP]DPX-JE874
Lot #: 2675-268
Specific activity: 64.61 µCi/mg
Radiochemical purity: >96%

Substance name: [14C-Phenylamino]DPX-JE874; [14C-PA]DPX-JE874
Lot #: 2868-107; 3048-238
Specific activity: 52.51 µCi/mg; 58.53µCi/mg
Radiochemical purity: 95%; 98.7%

Substance name: IN-JE874-92
Purity: 99.6%

Radiolabelling:

yes

Analytical method:

gas chromatography

high-performance liquid chromatography

mass spectrometry

Buffers:

A total of 148 mL of 0.02 M acetic add plus 352 mL of 0.02 M sodium acetate was transferred to a 1000-mL volumetric flask and diluted with deionized water to produce a 0.01 M pH 5.0 acetate buffer solution.

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

285 - 385

Duration:

7 d

Temp.:

25 °C

Initial conc. measured:

25 other: µg/L

Dark controls:

yes

Parameter:

other: Molar absorptivity

Value:

45 other: Per M/cm

Remarks:

at 291 nm

Parameter:

other: Molar absorptivity

Value:

127 other: Per M/cm

Remarks:

at 290 nm

Quantum yield (for direct photolysis):

0.975

DT50:

5 h

Test condition:

Darkness

Remarks on result:

other: The rapid rate of degradation was primarily due to hydrolysis because of the higher pH (7.75).

DT50:

3.9 h

Test condition:

In irradiated, non-sterile natural water

Remarks on result:

other: The rapid rate of degradation was primarily due to hydrolysis because of the higher pH (7.75).

Key result

DT50:

1.91 d

Test condition:

pH 5 under simulated sunlight

Remarks on result:

other: A conversion factor of 2.4 was used to obtain the half-life in natural sunlight equivalents, which was determined to be 4.6 days

Transformation products:

yes

Remarks:

IN-H3310, IN-JS940, IN-KF015, phenol, and IN-JL856

Validity criteria fulfilled:

yes

Conclusions:

Photolysis plays a major role in the degradation of the test substance in pH 5 buffer solution. However, photolysis of the test substance will likely be of little environmental importance due to the physical/chemical properties of the molecule (i.e. low water solubility, high sorption, hydrolytic instability, and low UV absorbance).

Executive summary:

The photolysis of the test substance was studied in aqueous, buffered solution at pH 5, the most hydrolytically stable pH. The study was conducted using test substance labeled separately with carbon-14 in the phenoxyphenyl ring and in the phenylamino ring. The rate of application was a nominal 25 µg/L (water solubility 52 µg/L). Test solutions were incubated under sterile conditions for up to 7 days in simulated sunlight at 25 ± 2°C. Dark controls for this study were run concurrently. An abbreviated experiment was also conducted in natural water (pH 7.75) under non-sterile conditions, both in the light and in darkness.

At pH 5, the test substance was degraded with a half-life of 4.6 days (r2 = 0.97) (dark control 41 days, r2 = 0.91) in actual natural sunlight equivalents. In irradiated, non-sterile natural water (pH 7.75), the test substance was rapidly degraded with a half-life of 3.9 hours (dark control 5.0 hours).

The quantum yield of the test substance was determined to be 0.975.

Several products were identified from the photolysis solutions using GC/MS and co-chromatography. Identified products included IN-Н3310, IN-JS940, IN-KF015, phenol, and IN-JL856. Polar, organic acids were tentatively identified, based on HPLC retention times. CO2 was trapped in 1 N NaOH and confirmed by precipitation as barium carbonate.

The major photolytic pathways yielded IN-Н3310, IN-JS940, and IN-KF015 from the phenoxphenyl portion of the test substance. Stable products from the phenylamino portion of the molecule were phenol, polar adds (fumaric, oxalic, and formic), and carbon dioxide.

Degradation rate data were obtained for IN-JL856, IN-KF015, IN-JS940, and IN-H3310. Only IN-H3310 and IN-KF015 were stable under photolytic conditions. IN-JS940 and IN-JL856 degrade to give IN-H3310.

Photolysis plays a major role in the degradation of the test substance in pH 5 buffer solution. However, photolysis of the test substance will likely be of little environmental importance due to the physical/chemical properties of the molecule (i.e., low water solubility, high sorption, hydrolytic instability, and low UV absorbance).

Description of key information

Study Type	Study Details	Value	Guideline	Reliability
Phototransformation in water	pH 5 under simulated sunlight; irradiated, non-sterile natural water (pH 7.75)	DT50 at pH 5= 1.91 days; DT50 in natural water = 3.9 hours	EPA 161-2	1

Key value for chemical safety assessment

Half-life in water:

3.9 h