Pyrasulfotole

Phototransformation in water

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 Jul 2003 - 09 Jan 2004

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: Canada PMRA DACO Number 8.2.3.3.2

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Analytical method:

high-performance liquid chromatography

Details on sampling:

- Sampling intervals for the parent/transformation products: 0, 1, 3, 7 and 9 d post-application
- Sampling method: Two replicates were removed from the water bath at each interval for each label.
- Sampling methods for the volatile compounds, if any: Volatiles were not collected
- Sampling intervals/times for pH measurements: 0, 1, 3, 7 and 9 d post-application
- Sampling intervals/times for sterility check: 0, 1, 3, 7 and 9 d post-application
- Sample storage conditions before analysis: All samples were analyzed within 2 d of the sampling interval date
- Other observation, if any (e.g.: precipitation, color change etc.): none

Buffers:

- pH: 7
- Type and final molarity of buffer: 0.01 M
- Composition of buffer: K2PO4 was dissolved in water (1.36 g per L) and the pH was adjusted to pH 7 by addition of 1 M potassium hydroxide.

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

< 290

Details on light source:

- Emission wavelength spectrum: < 290 nm
- Filters used and their purpose: Suprex (DSET) filter to limit emission wavelength to < 290 nm
- Light intensity at sample and area irradiated: 680 W/cm²
- Relative light intensity based on intensity of sunlight: Considering light intensity of an artificial light source calculated for 300-3000 nm, 58% of the light intensity is in the range of 300 to 800 nm.From the total radiant exposure measurement of 29.5 MJ/m², 17.1 MJ/m² was determined to be the daily irradiance (<800 nm) on June 23rd, 1988, in Phoenix, AZ (29.5 MJ/m² x 0.58 = 17.1 MJ/m²). Since the ozone layer effectively attenuates UV irradiation (< 290 nm) in the
atmosphere, and only the UV/visible absorption region is believed to be intense enough to drive photolytic reactions thus, the absorption region of interest is narrowed to 290-750 nm. The Suntest unit was operated at approximately 680 W/m2 (290-800 nm) to simulate highly photoreactive conditions. At this intensity it would take 7.0 hours in the Suntest unit to equal one solar day. Since 7.0 hours represents 1 environmental day, 212 hours of continuous irradiation at 680 W/m2 is equivalent to 30.3 environmental days (212 hours / 7.0 hours per day).
- Duration of light/darkness: Irradiated samples were continuously irradiated

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test apparatus/vessels: 20 mL quartz vessel
- Sterilisation method: 0.22 μm sterile filter (filtered after the addition of test substance); glassware was autoclaved
- Details of traps for volatile, if any: not performed
- If no traps were used, type of test system: closed system
- Indication of test material adsorbing to the walls of test apparatus: no

TEST MEDIUM
- Volume used/treatment: 20 mL
- Kind and purity of water: Purified with Milli-Q Gradient A10
- Preparation of test medium: A test solution with a concentration of 1 μg/mL was prepared as follows. An aliquot of [14C]-phenly labelled substance (315 μL, 40.0 μCi, 28.6 μCi/μMole) was obtained from the radiochemical repository. After solvent was removed from the solution by evaporation under a stream of nitrogen, the compound was re-dissolved in 500 mL of 0.01 M pH 7.0 buffer. The test substance concentration was determined by LSC (five aliquots of 100 μL).
A test solution with a concentration of 1 μg/mL was prepared as follows. An aliquot of [14C]-pyrazole labelled substance (540 μL, 76.7 μCi, 55.3 μCi/μMole) was obtained from the radiochemical repository. After solvent was removed from the solution by evaporation under a stream of nitrogen, the compound was re-dissolved in 500 mL of 0.01 M pH 7.0 buffer. The test substance concentration was determined by LSC (five aliquots of 100 μL).

REPLICATION
- No. of replicates (dark): 6
- No. of replicates (irradiated): 12

Duration:

9 d

Temp.:

25 °C

Initial conc. measured:

0.98 other: Pyrazole label: mg a.i./L

Duration:

9 d

Temp.:

25 °C

Initial conc. measured:

0.99 other: Phenyl label: mg a.i./L

Reference substance:

no

Remarks:

Reference standards were not used since limited degradation was observed

Dark controls:

yes

Preliminary study:

A preliminary study showed that no volatiles were generated; therefore no volatile traps were used in the study.

Test performance:

The test item did not degrade significantly in aqueous solution under continuous irradiation. Thus, no DT50 and DT90 values were determined.

Parameter:

max lambda

Value:

290 nm

% Degr.:

0.9

Sampling time:

9 d

Test condition:

Dark samples

Remarks on result:

other: not determined

Test condition:

Irradiated samples

Remarks on result:

other: Half-lives of the test substance were not calculated due to limited degradation.

Transformation products:

no

Remarks:

No major transformation products were formed in this study. Minor degradates did not exceed 4.1% of the applied radioactivity.

Details on results:

HALF-LIFE
- Half-lives of the test substance were not calculated due to limited degradation.

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS (distinguish between dark and irradiated samples)
- No major transformation products were formed in this study.

MINOR TRANSFORMATION PRODUCTS (distinguish between dark and irradiated samples)
- Minor degradates did not exceed 4.1% of the applied radioactivity and were not determined

Transformation of test item expressed as percentage of applied radioactivity (mean ± s.d.), in pH 7 buffer solution

		Sampling Times [days]
		Day 0	Day 1	Day 3	Day 7	Day 9
Test item	Irradiated	100.0±0.1	99.9±0.0	97.7±2.6	99.9±0.4	99.5±0.9
	Dark	100.0±0.1			100.7±1.1	99.6±1.0
Unknown A	Irradiated	0.0±0.0	0.0±0.0	2.0±2.9	0.0±0.0	0.0±0.0
	Dark	0.0±0.0			0.0±0.0	0.0±0.0
Total Extractable Residues	Irradiated	100.0±0.1	99.9±0.0	99.7±0.3	99.9±0.4	99.5±0.9
	Dark	100.0±0.1			100.7±1.1	99.6±1.0
CO2	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Volatile Organic	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Total Volatile Organic	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Bound to Apparatus Walls	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Total % Recovery	Irradiated	100.0±0.1	99.9±0.0	99.7±0.3	99.9±0.4	99.5±0.9
	Dark	100.0±0.1			100.7±1.1	99.6±1.0

Transformation of test item, expressed as percentage of applied radioactivity (mean ± s.d.), in pH 7 buffer solution.

		Sampling Times [days]
		Day 0	Day 1	Day 3	Day 7	Day 9
Test item	Irradiated	100.0±0.1	100.4±0.3	100.7±0.1	100.6±0.1	100.1±0.2
	Dark	100.0±0.1			100.2±0.0	102.0±1.2
Total Extractable Residues	Irradiated	100.0±0.1	100.4±0.3	100.7±0.1	100.6±0.1	100.1±0.2
	Dark	100.0±0.1			100.2±0.0	102.0±1.2
CO2	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Volatile Organic	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Total Volatile Organic	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Bound to Apparatus Walls	Irradiated	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a	n/a±n/a
	Dark	n/a±n/a		n/a±n/a	n/a±n/a	n/a±n/a
Total % Recovery	Irradiated	100.0±0.1	100.4±0.3	100.7±0.1	100.6±0.1	100.1±0.2
	Dark	100.0±0.1			100.2±0.0	102.0±1.2

Validity criteria fulfilled:

not applicable

Description of key information

No DT50 values were not derived due to insignificant degradation.

Additional information

One experimental study is available investigating the phototransformation of the test item in water (M-248236-02-1) which was performed according to EPA Guideline N 161-3. The aqueous phototransformation of radiolabelled test item in two positions was studied at 25 °C (± 0.2 °C) in sterile phosphate buffer solutions (0.01 M potassium phosphate) at pH 7 (range 6.95-7.16) at an initial concentration of 1 mg a.i./L under artificial irradiation (xenon lamp, >290 nm, quartz and Suprax filter). Samples were irradiated continuously for 9 d (equivalent to 30.3 environmental days). A preliminary study demonstrated that no volatiles were formed during photolysis. Therefore, test vessels were not connected to traps for the collection of CO2 and organic volatiles. Duplicate test systems were analyzed at 0, 1, 3, 7, and 9 d, by direct injection HPLC. In the dark test systems, the parent compound did not degrade. There were no major or minor transformation products detected. In the irradiated test systems, the parent compound decreased from 100 % of the applied amount at day 0 to 99.1 % of the applied at the end of irradiation. No major transformation products were detected. The minor transformation products were formed at a maximum of 2.0 % of the applied amount. All of the minor transformation products were transient in nature. The total unidentified radioactivity ranged from 0 to 4.1% of the applied amount. Average material balance for the test item samples was 99.8 ± 0.4% (range = 98.8 % to 100.2 %) of the applied amount. Material balance for the second radio-labelled samples was 100.4 ± 0.3% (range = 99.9% to 100.8%) of the applied amount. The half-life values were not calculated, due to insignificant degradation.