Reaction mass of 3-(difluoromethyl)-1-methyl-N-[(1RS,4SR,9RS)-1,2,3,4-tetrahydro-9-isopropyl-1,4-methanonaphthalen-5-yl]pyrazole-4-carboxamide and of 3-(difluoromethyl)-1-methyl-N-[(1RS,4SR,9SR)-1,2,3,4-tetrahydro-9-isopropyl-1,4-methanonaphthalen-5-yl]pyrazole-4-carboxamide; isopyrazam

Phototransformation in water

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

4 Jan 2008 to 10 Jun 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Study type:

direct photolysis

Qualifier:

according to guideline

Guideline:

other: OECD Draft Guideline: Phototransformation of Chemicals in Water Direct and Indirect Photolysis

Version / remarks:

August 2000

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Japanese Ministry of Agriculture guideline

Version / remarks:

Revised June 2001

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical method:

gas chromatography

liquid chromatography

high-performance liquid chromatography

mass spectrometry

other:

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

>= 290 - <= 800

Relative light intensity:

635

Duration:

35 d

Temp.:

25 °C

Initial conc. measured:

0.32

Reference substance:

no

Dark controls:

yes

% Degr.:

57.14

Sampling time:

35 d

Test condition:

Irradiated

Remarks on result:

other: Concentrated Buffer Solutions - Direct

Quantum yield (for direct photolysis):

0

Rate constant (for indirect photolysis):

other: days

DT50:

>= 81.9 - <= 84 d

Test condition:

continuous radiation

Remarks on result:

other: 30-50 °N - Summer _ Direct

DT50:

26 d

Test condition:

continuous irradiation

Remarks on result:

other: Direct

Transformation products:

not specified

Remarks:

M8, M9

- Material balance: The mean material balance of radioactivity in the irradiated test systems ranged from 92.8- 98.9% of the applied radioactivity (AR). The radioactivity associated with 14CO2 increased over the course of the study reaching a maximum of 2.0% AR by the end of the study period. The material balance of radioactivity in the dark control test systems was 62.2% and 94.2% of the applied radioactivity at Day 14 and 69.7% and 90.4% of the applied radioactivity at Day 35. The lower material balance in one of the replicates at each sampling interval was due to a loss of vessel contents. Tubing was attached to the side arms of the photolysis vessels and then to the filter and taps. The tubing attached to the dark controls remained more rigid than the tubing attached to the irradiated samples and was therefore not as secure on the vessel arms. The tubing for two of the samples did not remain attached to the vessel arms which allowed vessel contents to spill into the water bath. It is thought this was possible as the water bath sample tray (supplied with the water bath) was of different construction to that of the irradiated samples. This design was not as secure and the vessels may not have remained upright. The radioactivity associated with 14CO2 was below the limit of quantification. Results are presented in Table 1.

- Distribution and composition of radioactivity: All reported values are means of two replicates and four HPLC injections (two injections per replicate) unless otherwise stated. The [14C]-labelled test item photodegraded from 98.9% AR at zero time to 42.9% AR following 35 days constant irradiation. Two major (> 5% AR) degradation products were detected over the course of the study. A peak at ca 8.9 min was identified as M9 and reached a maximum of 10.7% AR at Day 21 before declining to 7.4% AR by the end of the study. A peak at ca 12.5 min was identified as M8 reaching a maximum of 9.9% AR at Day 21 before declining slightly to 8.6% AR by Day 35. A maximum of 19 minor unidentified transformation products were detected at any one time point and no individual unidentified component accounted for greater than ca 4.5% AR. The total levels of unidentified radioactivity accounted for a maximum of 32.1% AR at Day 35. No degradation was observed in the dark control samples indicating that the degradation in irradiated samples was due to photodegradation only. Unchanged test item and the degradation products M9 and M8 were identified using HPLC by comparing the retention time of the radioactive peak with that of an authentic standard. Selected samples were also analysed by TLC, a contrasting chromatographic system. The identity of unchanged test item and the degradation products M9 and M8 were confirmed under both chromatographic systems. Results are provided in Table 2.

- Rate of photodegradation: The rate of photolytic degradation of the [14C]-labelled test item was described using a first-order kinetic model (Table 3). The direct photolysis rate constant under continuous irradiation was calculated to be 0.03 day-1and the experimental half-life and DT90 values 26 days and 87 days, respectively.

- Determination of quantum yield: The photolytic susceptibility of the [14C]-labelled test item was assessed by means of quantum yield determination. The rate of photodegradation of the PNAP/pyridine was shown to be linear and the results are presented in Table 4 . Table 4 details the concentration of PNAP at each sampling interval. The PNAP/ pyridine actinometer experimental rate constant, half-life and DT90 values were 0.02 day-1, 32 days and 106 days, respectively. The molar absorption for the [14C]-labelled test item was calculated at the wavelength centres. The specific light absorption rate constant for the test item was derived from these absorbance readings and as these values were very close to the background, care should be taken when interpreting the quantum yield value. The quantum yield [Φ] for [14C]-labelled test item was determined to be: Φ (test item) = 1.013 x 10-5 molecules degraded/photon

- Direct photolysis rate constant and corresponding half-life at different latitudes: The direct photolysis rate constant derived from the continuous irradiation of the test item was adjusted for summer sunlight at 30°N, 40°N and 50°N. The results are presented in the following table 5. The corresponding half-life values are also reported. The continuous irradiation half-life value was also adjusted using the appropriate conversion factor to equivalent days of summer sunlight. 

Table 1. Distribution and Recovery of Radioactivity in Irradiated Samples and Dark Controls (Irradiated, results are expressed as a percentage of the applied radioactivity)

	Rep. No.	Sampling Interval (Days Irradiated)
		0	4	8	14	21	28	35
Irradiated Sample (Buffer Solution)	1 2	99.30 98.53	92.41 93.85	94.56 94.10	91.44 92.73	93.24 90.00	92.89 92.66	93.40 88.24
	Mean	98.92	93.13	94.33	92.09	91.62	92.78	90.82
NaOH Trap	1 2	ns ns	<LOQ <LOQ	0.44 0.36	0.85 1.06	1.53 2.21	1.42 1.51	1.08 2.81
	Mean	ns	<LOQ	0.40	0.96	1.87	1.47	1.95
Material Balance	1 2	99.30 98.53	92.41 93.85	95.00 94.46	92.29 93.79	94.77 92.21	94.31 94.17	94.48 91.05
	Mean	98.92	93.13	94.73	93.04	93.49	94.24	92.77

ns = no sample

<LOQ = sample recoveries below the level of quantification (liquid samples LOQ = 44 dpm above background)

Dark Controls, results are expressed as a percentage of the applied radioactivity

	Rep. No.	Sampling Interval (Days Irradiated)
		14	35
Sample (Buffer	1	62.10*	90.26
Solution)	2	94.06	69.60*
NaOH Trap	1 2	0.11 0.10	0.09 0.11
Material Balance	1 2	62.21 94.16	90.35 69.71

* Outliers caused by loss of buffer sample to the water bath.

Table 2. Characterization of the Irradiated Samples: Concentrated Buffer Solutions (Results expressed as % of applied radioactivity)

	Rep. No./ Injection No.	Sampling Interval (Days Irradiated)
		0	4	8	14	21	28	35
Syn-isomer test item	1/1 1/2	70.47 70.87	58.20 61.46	59.34 61.62	46.32 48.50	32.46 30.83	39.64 37.57	36.90 38.78
	2/1 2/2	70.91 70.71	60.08 62.96	59.89 57.53	46.74 45.18	32.11 30.98	35.58 31.48	22.04 26.04
	Mean	70.74	60.68	59.60	46.69	31.60	36.07	30.94
Anti-isomer test item	1/1 1/2	28.83 28.43	27.41 23.44	20.74 22.08	18.05 19.12	13.25 13.18	15.60 15.26	14.65 14.92
	2/1 2/2	27.62 27.82	23.00 21.98	22.43 19.63	18.61 18.30	11.31 13.56	13.61 13.66	9.49 8.62
	Mean	28.18	23.96	21.22	18.52	12.83	14.53	11.92
Total test item	1/1 1/2	99.30 99.30	85.61 84.90	80.08 83.70	64.37 67.62	45.71 44.01	55.24 52.83	51.55 53.70
	2/1 2/2	98.53 98.53	83.08 84.94	82.32 77.16	65.35 63.48	43.42 44.54	49.19 45.14	31.53 34.66
	Mean	98.92	84.63	80.82	65.21	44.42	50.60	42.86
M9	1/1 1/2	0.00 0.00	0.00 0.00	5.13 4.10	5.83 6.07	8.68 10.92	7.34 6.37	7.51 7.59
	2/1 2/2	0.00 0.00	0.00 0.00	6.09 3.75	5.70 5.80	12.10 11.20	8.67 8.24	6.89 7.42
	Mean	0.00	0.00	4.77	5.85	10.73	7.66	7.35
M8	1/1 1/2	0.00 0.00	3.94 5.53	3.43 4.13	6.51 5.45	10.16 9.23	7.22 6.08	6.14 6.83
	2/1 2/2	0.00 0.00	0.00 6.06	3.75 4.53	4.59 5.21	8.23 11.82	8.50 6.86	10.56 10.78
	Mean	0.00	3.88	3.96	5.44	9.86	7.17	8.58
Sum of Unidentified Radioactivity*	1/1	0.00	2.86	5.93	14.75	28.69	23.09	28.19
	1/2	0.00	1.98	2.62	12.30	29.09	27.62	25.30
	2/1	0.00	10.76	1.93	17.07	26.26	26.30	39.22
	2/2	0.00	2.85	8.67	18.23	22.46	32.44	35.37
	Mean	0.00	4.63	4.79	15.59	26.64	27.41	32.06

* no individual unidentified component accounts for greater than ca 4.5 % AR.

Table 3. Photolysis Rate Constants and Half-Life Values for [14C]-labelled test item and PNAP/Pyridine Actinometer (Irradiation)

	Kd (day-1)	Half-Life (days)
[14C]-labelled test itm	0.0265309	26
PNAP/Pyridine Actinometer	0.0216695	32

Table 4 Analysis of the PNAP/Pyridine Actinometer

Sampling Interval (Days)	Mean Concentration PNAP (Mol/L)	Mean [PNAP] Remaining (%)
0	9.990E-06	100.00
3	9.391E-06	94.01
7	8.615E-06	86.24
11	7.864E-06	78.72
14	7.385E-06	73.93

Table 5. Direct photolysis rate constant and corresponding half-life at different latitudes

Latitude/ Season	Direct Photolysis Rate Constant (day-1)	Half-Life (days)	half-life corrected for equivalent days of summer sunlight (days)
30˚N/ Summer	0.0293614	23.61	81.90
40˚N/ Summer	0.0289469	23.95	81.90
50˚N/ Summer	0.0277116	25.01	83.98

 

Validity criteria fulfilled:

not specified

Conclusions:

In a photochemical degradation study conducted in accordance with a draft OECD test guideline, EPA 161-2 and JMAFF-12 Nohsan No 8147, the direct photolytic half-life for the test substance was calculated to be 26 days and the quantum yield was calculated as 1.01e-05 molecules degraded/photon. The half-life value corrected for days equivalent of summer sunlight was 81.9- 84 days at latitudes of 30-50°N.

Executive summary:

The rate of photochemical degradation of the [14C]-labelled test item and its subsequent quantum yield have been determined following JMAFF-12 Nohsan No 8147, draft OECD test guideline and EPA 161-2 guideline to GLP compliance. The study was conducted under simulated sunlight in pH 7 phosphate buffer for 35 days under continuous irradiation at 25 ± 2°C. [Pyrazole-5-14C]- labelled test item was applied at a rate of 0.3195 µg/mL, to pH 7 phosphate buffer in individual quartz glass photolysis vessels. The samples were irradiated under a xenon arc lamp using an accelerated exposure table unit and maintained at 25 ± 2°C. The lamp was equipped with filters to eliminate emitted wavelengths of < 290 nm and reduce wavelengths greater than 800 nm to give a spectral distribution similar to natural sunlight. Non-irradiated (dark control) samples were also prepared and maintained in the dark at 25 ± 2°C. Duplicate samples were analysed immediately following test item application (zero time) and after the following time periods of irradiation; 4, 8, 14, 21, 28 and 35 days. Duplicate dark control samples were analysed following 14 and 35 days incubation in the dark. 

Material balance, calculated as the percent of applied radioactivity (% AR), was maintained in the irradiated samples throughout the study with mean values in the range 92.8% AR to 98.9% AR. The radioactivity associated with 14CO2 also increased slightly over the course of the study reaching a maximum of 2.0% AR by Day 35. HPLC analysis of pH 7 phosphate buffer irradiated solution demonstrated that the [14C]- labelled test item was degraded. [14C]-labelled test item decreased from 98.9% AR (Day 0) to 42.9% AR by Day 35. Two major (>5% AR) photodegradation products, M9 and M8 were detected over the course of the study. M9 reached a maximum of 10.7% AR at Day 21 before declining to 7.4% AR by the end of the study. M8 reached a maximum of 9.9% AR at Day 21 before declining slightly to 8.6% AR at Day 35. A maximum of 19 minor (<5% AR) unidentified photodegradation products were detected at any one time point. The total levels of unidentified radioactivity accounted for a maximum of 32.1% AR at Day 35. No degradation was apparent in the dark control samples indicating that the degradation in irradiated samples was due to photodegradation only. The half-life and DT90 of the [14C]-labelled test item were calculated using the SFO model. The half-life and DT90 of the [14C]-labelled test item under continuous irradiation were 26 days and 87 days, respectively. The half-life value corrected for days equivalent of summer sunlight was 82 days at latitudes of 30°N and 40°N and 84 days at 50°N. For calculation of the quantum yield, the number of photons reaching the test solution was determined under the same conditions, using a P-nitroacetophenone (PNAP) actinometer. The quantum yield for the [14C]-labelled test item was calculated as 1.01E-05 molecules degraded/photon. However, as the specific light absorption rate constant for the test item was derived from absorbance readings that were close to the background, care should be taken when interpreting the quantum yield value.

 

Reference 2

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

20 Jun 2006 to 16 Oct 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Study type:

other: direct and indirect photolysis

Qualifier:

according to guideline

Guideline:

other: Japanese Ministry of Agriculture, Forestry and Fisheries, Test Data for Registration of Agricultural Chemicals, 12 Nousan No 8147, Agricultural Production Bureau

Version / remarks:

November 24, 2000 revised 26th June 2001

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OECD Guidelines for the Testing of Chemicals, Phototransformation of Chemicals in Water- Direct and Indirect Photolysis

Version / remarks:

Draft, August 2000

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

October 18, 1982

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical method:

gas chromatography

liquid chromatography

high-performance liquid chromatography

mass spectrometry

other:

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

>= 295 - <= 800

Duration:

29 d

Temp.:

25 °C

Initial conc. measured:

0.5 other: μg/ml

Reference substance:

no

Dark controls:

yes

% Degr.:

24.2

Sampling time:

29 d

Test condition:

Irradiated

Remarks on result:

other: Phenyl Labelled - Direct

% Degr.:

28.1

Sampling time:

29 d

Test condition:

Irradiated

Remarks on result:

other: Pyrazole Labelled - Direct

% Degr.:

87.8

Sampling time:

29 d

Test condition:

Irradiated

Remarks on result:

other: Phenyl Labelled - Indirect

% Degr.:

90.4

Sampling time:

25 d

Test condition:

Irradiated

Remarks on result:

other: Pyrazole Labelled - Indirect

DT50:

>= 60.6 - <= 63.5

Test condition:

Days Summer Sunlight at 30, 40 and 50°N (OECD Calculation)

Remarks on result:

other: mean of both pyrazole & phenyl labels - Direct

DT50:

>= 5.6 - <= 5.9

Test condition:

Days Summer Sunlight at 30, 40 and 50°N (OECD Calculation)

Remarks on result:

other: Phenyl labelled - Indirect

DT50:

>= 5.2 - <= 5.5 h

Test condition:

Days Summer Sunlight at 30, 40 and 50°N (OECD Calculation)

Remarks on result:

other: Pyrazole labelled - Indirect

DT50:

1 302.8 h

Test condition:

Continuous Irradiation

Remarks on result:

other: mean of both pyrazole & phenyl labels - Direct

DT50:

101 h

Test condition:

Continuous Irradiation

Remarks on result:

other: pyrazole labelled - Indirect

DT50:

116.7 h

Test condition:

Continuous Irradiation

Remarks on result:

other: phenyl labelled - Indirect

DT50:

176 d

Test condition:

Tokyo Spring Sunlight (using JMAFF Calculation)

Remarks on result:

other: mean of both pyrazole & phenyl labels - Direct

DT50:

15.2 d

Test condition:

Tokyo Spring Sunlight (using JMAFF Calculation)

Remarks on result:

other: Pyrazole labelled - Indirect

DT50:

16.4 d

Test condition:

Tokyo Spring Sunlight (using JMAFF Calculation)

Remarks on result:

other: Phenyl labelled - Indirect

Transformation products:

not specified

Remarks:

M8, M9

Results of the direct photolysis study are given in Tables 1 (radioactivity distribution), 2 (substance identity, pyrazole label) and 3 (substance identity, phenyl label).

Table 1. Mass balance and radioactivity distribution in the direct photolysis study with the test item

Fraction	Rep.	Incubation time (days)
		0	3	8	11	15	21	29
Aqueous	Pyrazole	103.2	103.3	102.4	106.9	104.8	103.8	104.4
	Phenyl	102.8	100.7	100.4	101.4	104.5	103.4	98.6
14CO2	Pyrazole	n/a	0	0.7	0.1	1.3	1.3	1.5
	Phenyl	n/a	0	0.2	0.3	0.7	1.3	2.2
TOTAL	Pyrazole	103.2	103.3	103.1	107.0	106.1	105.1	105.9
	Phenyl	102.8	100.7	100.6	101.7	105.2	104.7	100.8
Mean ± SD		103.6 ± 2.1

Table 2. Substance distribution in the direct photolysis study with the test item (pyrazole label)

ID	Incubation time (days)
	0	3	8	11	15	21	29
Test item	103.2	99.2	69.1	90.3	63.1	63.7	71.9
M8	0	1.0	11.5	5.1	14.8	14.8	10.9
M9	0	0	4.7	1.5	7.4	6.6	4.4

Table 3. Substance distribution in the direct photolysis study with the test item (phenyl label)

ID	Incubation time (days)
	0	3	8	11	15	21	29
Test item	102.8	100.0	95.8	97.2	94.4	86.7	75.8
Polar (2.5 mins)	0	0	0	0	0	1.2	1.8
Polar (4.5 mins)	0	0	0	0	0	0	0

It will be noted that the amount of parent and metabolites do not match the amount of radioactivity in the aqueous phase presented in Table 1. It was explained that the remaining radioactivity was "streaked‟ along the chromatograms. This represented a number of minor components, none of which constituted more than 5% AR. No degradation was observed in the dark controls. The DT50 values were calculated using the ModelManager v 1.1 software for the combined dataset of pyrazole and phenyl label tests, as these are effectively replicates. This was not performed to full FOCUS kinetics guidance, but is reasonable. The DT50 for the study conditions for both labels was 54.3 days with an r2 value of 0.44. This reflects what is essentially a scattered database of experimental values. The DT50 was also extrapolated to almost twice the study duration. This DT50 equates to DT50 values of 61 – 64 days summer sunlight at 30 – 50 ºN assuming 12 hour days. Indirect photolysis was conducted as well. Incubations using sterilised natural water (Middle Row Pond, UK; pH 7.34, total carbon 44.2 mg/L, total nitrogen 3.0 mg/L). Results are only reported briefly as this type of study is generally not used in the risk assessment. Under essentially the same photolysis conditions as for the direct photolysis test, test item degraded much faster than in sterile buffer with experimental DT50 of 4.2 – 4.9 days, equivalent to 5.2 – 5.9 days summer sunlight at 30 – 50ºN assuming 12 hour days. Peak concentration of M8 was 36.4% at study end (25 days). Peak concentration of M9 was 20.1 % AR at study end (25 days). 

Validity criteria fulfilled:

not specified

Conclusions:

In a photodegradation study performed in accordance with a draft OECD test guideline, EPA 161-2 and JMAFF-12 Nohsan No 8147, the DT50 was estimated to be 60 - 64 days of summer sunlight (calculated for latitudes of 30, 40 and 50°N), equivalent to 176 days Tokyo spring sunlight.

Executive summary:

The aqueous photolysis of the [14C]-labelled test item was studied according to a draft OECD test guideline on phototransformation of chemicals in Water, EPA 161-2 and JMAFF-12 Nohsan No 8147. The study was in compliance with GLP. The photolysis of the test item was investigated in sterile natural water (indirect photolysis) and a sterile pH 7 phosphate buffer (direct photolysis). The 14C-labelled test items (both 14C-phenyl and 14C-pyrazole labelled) were applied, at rates equivalent to ca. 0.5 μg/mL, to the aqueous media in individual photolysis vessels. Aliquots (15 mL) were continuously irradiated using light from a xenon arc lamp. The emitted light was filtered to give a spectral distribution close to that of natural sunlight. The samples were maintained at 25 ± 2°C and were irradiated for periods at least the equivalent of 30 days summer sunlight (at latitudes 30 - 50°N). In the indirect photolysis test, duplicate samples per 14C-label were taken for analysis at up to 9 intervals during irradiation. In the direct photolysis test, duplicate samples (one 14C-phenyl labelled and one 14C-pyrazole labelled) were taken for analysis up to 7 intervals during irradiation. During irradiation, volatile products were trapped, using a flow-through system, in a 2M sodium hydroxide solution. Two sets of ‘dark control’ samples were also prepared and maintained at ca. 25°C. Dark controls were removed for analysis at 2 intervals, at the time equivalent to the irradiation period of (a) ca. 30 days Tokyo spring sunlight and (b) ca. 30 days summer sunlight at latitude 50ºN. 

In the indirect photolysis tests, the mass balance ranged from 89.8 - 103.7% of applied radioactivity. In the direct photolysis test, the mass balance ranged from 103.1 - 107.0% of applied radioactivity. The recovery from dark control samples was 100.3 - 105.2% of applied radioactivity. Both direct and indirect photodegradation of the test substance was shown to follow the same pathway, however, the rate of indirect photolysis was found to be approximately 10 times faster than direct photolysis. In the indirect photolysis tests, the evolution of 14CO2 accounted for up to 10.7% and 18.1% of applied radioactivity in the 14C-pyrazole and 14C-phenyl labelled samples, respectively. The evolution of 14CO2 in the direct photolysis test was negligible and accounted for up 1.5% and 2.2% of applied radioactivity in the 14C-pyrazole and 14C-phenyl labelled samples, respectively. Degradation involved cleavage of the molecule between the two ring systems to yield the carboxylic acid and amide derivatives of the pyrazole ring. Mineralization was more predominant in 14C-phenyl labelled samples than in the 14C-pyrazole labelled samples. This was assumed to reflect the extensive degradation of the 14C-phenyl moiety following cleavage between the two ring systems. The ratio of the syn- and anti-isomers remained consistent throughout the irradiation for all tests, indicating that no isomer-specific degradation had occurred. No significant degradation was apparent in all the ‘dark controls’ indicating that the degradation in irradiated samples was due to photodegradation only.

The photolytic half-lives (DT50) were calculated to be 101 hours and 116.7 hours under indirect photolysis for 14C- pyrazole and 14C-phenyl labelled test substance, respectively, using first-order kinetics (SFO). The DT50 was 1302.8 hours for labels combined substance under direct photolysis.
The corrected DT50 values for different latitudes and Tokyo spring were calculated as well. For direct photolysis, the DT50 was estimated to be 60 - 64 days summer sunlight at latitudes 30 - 50°N (using the calculation specified in the OECD test guideline). The half-life was also estimated (using the calculation specified in the JMAFF test guideline) as 176 days Tokyo spring sunlight.

Description of key information

DT50 = 60 – 64 days (summer sunlight latitudes of 30 - 50°N), direct irradiation with continuous light by Xenon arc lamp (wavelength >= 290 nm and < 800 nm), 25 °C, EPA 161-2, OECD draft guideline and JMAFF-12 Nohsan No 8147, Kuet, 2008

DT50 = 82 - 84 days (summer sunlight latitudes of 30°N- 50°N), direct irradiation with continuous light by Xenon arc lamp (wavelength >= 290 nm and < 800 nm), Quantum yield of 1.01E-5 molecules degraded/photon, 25 °C, EPA 161-2, OECD draft guideline and JMAFF-12 Nohsan No 8147, Wardrope 2008

Additional information

Two direct photolysis studies (EPA 161-2, OECD draft guideline and JMAFF-12 Nohsan No 8147) with continuous irradiation (xenon arc; wavelengths > 290 nm and < 800 nm) at 25 ± 2˚C are available. One study (Kuet 2008) investigated the photolysis of 14C-phenyl and 14C-pyrazole labelled substances in a sterile natural water (indirect photolysis) and a sterile pH7 phosphate buffer (direct photolysis). The results show that in direct photolysis condition, the DT50 of the substance was estimated to be 60 – 64 days of summer sunlight at latitudes of 30°N - 50°N at pH 7. The rate of indirect photolysis was found to be approximately 10 times faster than direct photolysis. The second study (Wardrope 2008) investigated the photolysis of Pyrazole-5-14C labelled test substance under simulated sunlight in pH 7 phosphate buffer for 35 days. The result indicates that the DT50 of the substance was 26 days, which is equivalent to 82 - 84 days of summer sunlight at latitudes of 30°N - 50°N. In addition, the quantum yield of direct phototransformation in water was determined to be 1.01E-05 molecules degraded/photon.