Pirimiphos-methyl

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:

3 Feb 2005 to 27 Jun 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Study type:

direct photolysis

Qualifier:

according to guideline

Guideline:

other: JMAFF Agchem Test Guidelines 12 Nousan N. 8147

Version / remarks:

24 November 2000, revised 26 June 2001: Photodegradation in Water (2-6-2)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: OECD Guideline for Testing of Chemicals, phototransformation of Chemicals in water

Version / remarks:

draft document, August 2000

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical method:

high-performance liquid chromatography

mass spectrometry

other: Thin-Layer Chromatography (TLC); Liquid Scintillation Counting (LSC), Nuclear Magnetic Resonance (NMR) spectroscopy

Details on sampling:

- Sampling intervals: Duplicate irradiated samples were taken after 0, 0.5, 1 and 4 hours and after 1, 3, 5, 7, 10 and 15 days of irradiation. Single dark control samples were taken after 0, 1, 3, 5, 7, 11 and 15 days.

Light source:

Xenon lamp

Remarks:

1.8 kW xenon burner and an UV filter system

Light spectrum: wavelength in nm:

> 300 - <= 400

Relative light intensity:

56.5

Details on light source:

- Xenon Burner: Max. 765 W/m2 at max. UV filtering (lambda < 800 nm) with irradiance between 400 W/m2 and 765 W/m2 to a pre-set value.
- Filters: UV filter with a 290 nm cut-off to simulate natural sunlight.
- Total exposure area: Approximately 500 cm2
- Vessel exposed area: 28.26 cm2

Details on test conditions:

TEST SYSTEM
- Test vessels: Cylindrical glass vessels; covered with quartz glass plates (to cut off radiation below 290 nm similarly to the natural sunlight cut-off by ozone), which were screwed on top of the vessel. The light was allowed to enter the solution only from the top of the vessel.
- Sterilisation method: All glass equipment was sterilised prior to use by rinsing with an ethanol/water (70:30; v/v) solution.
- Details on prevent evaporation of the test item: Filtered, humidified air was continuously drawn through the incubation vessels at about 30 mL/minute from day 1 onwards due to the high vapour pressure of the test item. This reduced any evaporation of the test item during its irradiation.
- Details of traps for volatile: Any radioactive carbon dioxide or volatile compounds in the purged air was captured in traps containing about 50 mL ethylene glycol and 2N NaOH. Trapping solutions were exchanged at each sampling interval with the exception of the very short sampling intervals until day 1. No trapping of volatiles was performed for these short time samples due to the high vapour pressure of the test item.

TEST MEDIUM
- Volume used/treatment: 85 mL of test solution
- Source and properties of natural water: Table 1 in 'Any other information on materials and methods incl. tables'
- Preparation of test solution: The radiolabelled test item was transferred to a 5 mL measuring flask and the volume made up to the mark with acetonitrile (application solution). The total amount of 14C-lablled test substance present in the solution was determined by liquid scintillation counting (LSC). Based on the total radioactivity measured (1'274'210 dpm per 10 μL) and the specific activity of 2.61 MBq/mg, the concentration of the solution was calculated to be about 0.814 mg 14C-labelled test substance/mL.
- Application of test solution: For the irradiated samples, individual applications were performed at each vessels grouped by each sampling time. For this purpose, volumes of 85 mL sterile pond water were separately transferred to the reaction vessels followed by 110 μL of the application solution. The resulting solutions were mixed thoroughly. The final content of the co-solvent acetonitrile was below 0.2%. For the dark controls a batch application was performed. Therefore, 250 mL aliquots of sterile pond water were transferred to a measuring cylinder, followed by 390 μL of the application solution. The resulting solution was mixed thoroughly. Thereafter, 20 mL aliquots were separately transferred to the previously sterilised test vessels using a sterile pipette.
- Sterility of the test solutions: The sterility of the irradiated and control solutions was checked by plate counts at the start and end of the 15-day irradiation/incubation period. A single aliquot (0.5 mL) of the test solution was uniformly distributed onto the surface of agar plates and then incubated at room temperature for up to 7 days. In addition, a positive control (1 mL tap water) and a negative control (1 mL sterile water) were incubated under the same conditions. The colonies that developed on these plates were counted.
- pH: 8.3 - 8.7 for all samples

REPLICATION
- No. of replicates (dark control): 1 (containing about 20 mL test solution)
- No. of replicates (irradiated): 2

Duration:

15 d

Temp.:

25 °C

Initial conc. measured:

1.047 mg/L

Reference substance:

no

Dark controls:

yes

Remarks:

0.948 mg 14C-labelled test substance/L

Computational methods:

The photolytic half lives (DT50 and DT90-values) of the test item and one of its major degradation products were calculated by applying first-order (parent) or consecutive first order (major degradation product) reaction kinetics.

Preliminary study:

not performed

Test performance:

not reported

Parameter:

not specified

% Degr.:

94

Sampling time:

1 h

Test condition:

irradiated

Remarks on result:

other: expressed as applied radioactivity of the parent compound

% Degr.:

3.2

Sampling time:

1 h

Test condition:

dark control

Remarks on result:

other: expressed as applied radioactivity of the parent compound

% Degr.:

23.7

Sampling time:

15 d

Test condition:

dark control

Remarks on result:

other: expressed as applied radioactivity of the parent compound left at the end of the study

Key result

DT50:

0.07 d

Test condition:

Irradiated

Remarks on result:

other: equivalent to natural Tokyo spring sunlight at latitude 35°N

DT50:

0.02 d

Test condition:

Irradiated

Remarks on result:

other: equivalent to natural summer sunlight for latitude 30 °N - 50 °N

DT50:

0.01 d

Test condition:

irradiated

Remarks on result:

other: experimental result, continuous irradiation (56.5 W/m2)

Transformation products:

yes

Remarks:

See additional information provided in overall endpoint summary.

Details on results:

An overview of the results is provided in Table 2 - Table 7 in 'Any other information on results incl. tables'.

- Material balance: The total mean recoveries from the irradiated and dark control samples during the study were 98.0 ± 2.4% and 95.2 ± 3.1 % of the applied radioactivity, respectively.

- Photodegradation of 14C-labelled test substance: 14C-labelled test substance was very rapidly photo-degraded in natural pond water. Under
irradiation the amount of 14C-labelled test substance decreased from initially 100.0% to 6.0% within 1 hour (0.04 days) and was no longer detected thereafter. Besides the test item, up to twelve radioactive fractions were detected by HPLC. Five of which exceeded 10% of the applied radioactivity. The amount of radioactive carbon dioxide in the irradiated samples increased continuously to 3.6% of the applied radioactivity at the end of irradiation.
The most significant photo-degradate was M1, identified by co-chromatography using HPLC and 2D-TLC. It reached its maximum amount of 78.5% after 4 hours (0.17 days) and decreased to 3.0% by the end of irradiation. Other major unidentified metabolites 5, 11 and 12 were formed more slowly mainly by further photolysis of M1. Unknown metabolite 5 reached its highest concentration of 18.3% on day 10 and decreased thereafter to 15.6% after 15 days of irradiation. Unknown metabolite 11 increased up to 38.6% within 5 days then remained at this plateau value from day 5 onwards until the end of irradiation. Unknown metabolite12 increased throughout the study reaching a maximum amount of 21.4% on day 15. All other metabolites were individually ≤ 4.9% (mean values) with the exception of unknown metabolite 1 reaching 9.8% after 0.02 days of irradiation decreasing to 2.8% after 0.17 days. When the irradiated samples of day 15 were analysed by TLC, contrary to the previous HPLC analysis, four major radioactive fractions amounting to 14.3%, 20.3%, 12.8% and 14.6% of the applied radioactivity were detected. Since M1 represented only 3.0% by HPLC at this time, it was assumed that unknown metabolite 11 (HPLC metabolite) consisted of probably two components and that an additional major metabolite was present, not separated by the conditions used. This additional metabolite was also detected by the HPLC method used for LC-NMR. The major metabolites were identified by LC-MS and LC-NMR. Based on the retention times on HPLC unknown metabolite 5 corresponded to the proposed structure for M7, unknown metabolite 11a to the proposed structure for M8 and unknown metabolite 12 to the proposed structure for M10. The additional unknown metabolite 11b was identified as M9.

- Dark control: The parent compound was shown to be stable in the dark for at least 1 day. Therefore the degradation in the irradiated samples was due to photolysis only. The degradation under dark conditions was prolonged until day 15. It was however observed that the test item slowly hydrolyses in the pond water. 14C-labelled test substamce was degraded from 100% initially to 76.3% within 15 days of incubation. Three minor metabolites were detected including M1. Unknown metabolite 3 was the most significant degradate, reaching its highest amount of 8.2% at study end. Virtually no carbon dioxide was formed in the dark controls (≤ 0.1 %).

Table 2. Material Balance of radioactivity in the irradiated samples. Results shown in % of the applied radioactivity (a) and in mg parent equivalents per litre (b).

a)

Irradiated sterile pond water		Irradiation Time in days
	[Suntest]	0	0.02	0.04	0.17	1	3	5	7	10	15
	[Sunlight]^1	0	0.15	0.29	1	7	22	36	51	73	109
	[Sunlight]^2	0	0.04	0.09	0.38	2	7	11	16	22	34
	% Applied
Radioactivity in sample	A	100	97.1	97.3	98.1	97.2	96.5	101.2	92.8	95.7	90.2
	B	100	97.7	99	97.1	96.7	97.4	103.5	94.8	94	92.3
	Mean	100	97.4	98.1	97.6	97	97	102.4	93.8	94.9	91.2
14CO2	A	n.p.	n.p.	n.p.	<I.d.	<l.d.	0.5	1	2	3	3.7
	B	n.p	n.p.	n.p.	<l.d.	0.1	0.6	1.4	2.6	3.5	3.5
	Mean	n.p.	n.p.	n.p.	<l.d.	<l.d.	0.6	1.2	2.3	3.2	3.6
Total	A	100	97.1	97.3	98.1	97.3	97.1	102.2	94.9	98.7	93.9
	B	100	97.7	99	97.1	96.8	98	104.9	97.4	97.5	95.8
Mean ± SD		98.0 ± 2.4

b)

Irradiated sterile pond water		Irradiation Time in days
	[Suntest]	0	0.02	0.04	0.17	1	3	5	7	10	15
	[Sunlight]^1	0	0.15	0.29	1	7	22	36	51	73	109
	[Sunlight]^2	0	0.04	0.09	0.38	2	7	11	16	22	34
	mg/L
Radioactivity in sample	A	1.038	1.007	1.009	1.018	1.009	1.002	1.05	0.963	0.993	0.936
	B	1.038	1.014	1.027	1.007	1.003	1.011	1.074	0.984	0.975	0.957
	Mean	1.038	1.011	1.018	1.013	1.006	1.006	1.062	0.974	0.984	0.946
14CO2	A	n.p.	n.p.	n.p.	<l.d.	<l.d.	0.006	0.01	0.021	0.031	0.039
	B	n.p.	n.p.	n.p	<l.d.	<l.d.	0.006	0.015	0.027	0.036	0.036
	Mean	n.p.	n.p.	<0.001	<l.d.	<l.d.	0.006	0.013	0.024	0.034	0.037
Total	A	1.038	1.007	1.009	1.018	1.009	1.007	1.061	0.984	1.024	0.974
	B	1.038	1.014	1.027	1.007	1.004	1.017	1.089	1.011	1.012	0.994
Mean ± SD		1.017 ± 0.025

A/B: Replicates
SD: Standard deviation
n.p. : not performed
l.d.: limit of detection
1 Corresponding to Tokyo, Japan (35°N latitude) spring sunlight
2 natural summer sunlight at latitude 30 to 50°N

Table 3. Material Balance of radioactivity in the dark control samples. Results shown in % of the applied radioactivity (a) and in mg parent equivalents per litre (b).

a)

Dark control	Incubation Time in days
sterile pond water	0	1	3	5	7	11	15
	(% applied)
Radioactivity in sample without backwash	100	96.8	80.2	90.2	78.1	87	83.4
Backwash with acetonitrile	n.p.	n.p.	15.6	6.5	13.1	6.9	8.6
Total Radioactivity in sample	100	96.8	95.8	96.7	91.2	93.9	92
14 CO2	n.p.	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	<0.1
Total	100	96.8	95.8	96.7	91.2	93.9	92
Mean ± SD	95.2 ± 3.1

b)

Dark control	Incubation Time in days
sterile pond water	0	1	3	5	7	11	15
	(mg/I)
Radioactivity in sample without backwash	0.948	0.918	0.76	0.856	0.739	0.825	0.792
Backwash with acetonitrile	n.p.	n.p.	0.148	0.061	0.125	0.065	0.081
Total Radioactivity in sample	0.948	0.918	0.908	0.917	0.864	0.89	0.873
14CO2	n.p.	< l.d.	< l.d.	< l.d.	< l.d.	< l.d.	< l.d.
Total	0.948	0.918	0.908	0.917	0.865	0.891	0.873
Mean ± SD	0.903 ± 0.029

n.p.: Not performed
SD: Standard deviation
l.d.: limit of detection

Table 4. Degradation of 14C-labelled test substance in the irradiated samples. Results are shown in % of the applied radioactivity.

Irradiated pond water pattern (% applied)		Irradiation Time in days
	[Suntest]	0	0.02	0.04	0.17	1	3	5	7	10	15
	[Sunlight]^1	0	0.15	0.29	1.23	7	22	36	51	73	109
	[Sunlight]^2	0	0.04	0.09	0.38	2	7	11	16	22	34
Test substance	A	100	28.4	7.2	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.
	B	100	23.5	4.9	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.
	Mean	100	25.9	6	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	<1.d.	<l.d.
Unknown 1	A	<l.d.	8.8	7.3	3	2	0.8	2.7	2.2	3.8	<l.d.
	B	<l.d.	10.7	6.1	2.6	2.2	3.7	2.6	1.6	3.7	<l.d.
	Mean	<l.d.	9.8	6.7	2.8	2.1	2.3	2.7	1.9	3.8	<l.d.
Unknown 2	A	<l.d.	<l.d.	2.8	3	1.1	2.8	2.3	2.6	1	1.7
	B	<l.d.	<l.d.	4.7	2.1	2.2	1.6	3	1.3	0.8	1.9
	Mean	<l.d.	<I.d.	3.7	2.5	1.6	2.2	2.6	1.9	0.9	1.8
Unknown 3	A	<l.d.	3.8	3.7	2.4	1	3.7	1.1	1.9	1.8	1.6
	B	<l.d.	4.3	3.4	1.4	3.5	0.4	1.1	1.2	2.4	2.3
	Mean	<l.d.	4	3.6	1.9	2.2	2	1.1	1.5	2.1	2
M1	A	<l.d.	56.2	74.7	77.6	64.8	33.9	17.7	12.8	5.5	2.9
	B	<l.d.	59.3	78.1	79.5	56.5	26	13.6	8.5	4.8	3
	Mean	<l.d.	57.7	76.4	78.5	60.7	30	15.7	10.7	5.2	3
Unknown 5	A	<l.d.	<l.d.	<l.d.	2.8	5.2	10.1	12.3	11.2	16.4	16.9
	B	<l.d.	<l.d.	<l.d.	2.6	2.3	9	16	13.1	20.2	14.3
	Mean	<l.d.	<l.d.	<l.d.	2.7	3.8	9.5	14.1	12.2	18.3	15.6
Unknown 6	A	<l.d.	<1.d.	<l.d.	1.5	2.3	<l.d.	<l.d.	3.4	<l.d.	<l.d.
	B	<l.d.	<l.d.	<l.d.	1.9	3	<l.d.	1.2	3.8	<l.d.	<l.d.
	Mean	<l.d.	<l.d.	<l.d.	1.7	2.6	<l.d.	0.6	3.6	<l.d.	<l.d.
M3	A	<l.d.	<l.d.	<l.d.	1.2	0.6	3.6	3.7	<l.d.	<l.d.	3.8
	B	<l.d.	<l.d.	<l.d.	1.2	0.9	4.7	5.3	3.2	<l.d.	3.8
	Mean	<l.d.	<l.d.	<l.d.	1.2	0.8	4.1	4.5	1.6	<l.d.	3.8
Unknown 8	A	<l.d.	<l.d.	<l.d.	<I.d.	<l.d.	2.4	5.5	4	5.4	4.5
	B	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	3.9	4.4	3.4	4.4	4.4
	Mean	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	3.1	4.9	3.7	4.9	4.5
Unknown 9	A	<l.d.	<1.d.	<1.d.	<l.d.	<l.d.	1.1	0.8	1.1	1.7	1.3
	B	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	1.2	0.8	1.1	1.4	1.2
	Mean	<l.d.	<l.d.	<l.d.	<l.d.	<l.d.	1.2	0.8	1.1	1.5	1.3
Unknown 10	A	<l.d.	<l.d.	<l.d.	<l.d.	0.6	2.9	4.2	4.4	4.3	2.3
	B	<l.d.	<l.d.	<l.d.	<l.d.	1	4.3	4.1	3.2	1.4	2.2
	Mean	<l.d.	<l.d.	<l.d.	<l.d.	0.8	3.6	4.1	3.8	2.9	2.3
Unknown 11	A	<l.d.	<l.d.	1.6	6.7	17.6	28	38.2	33.7	36.9	35.3
	B	<l.d.	<l.d.	1.8	5.9	22.7	33.9	39	38.3	39.5	36.1
	Mean	<l.d.	<l.d.	1.7	6.3	20.1	31	38.6	36	38.2	35.7
Unknown 12	A	<l.d.	<l.d.	<l.d.	<I.d.	2.1	7.2	12.8	15.5	18.9	19.9
	B	<l.d.	<l.d.	<l.d.	<l.d.	2.3	8.7	12.3	16.1	15.3	22.9
	Mean	<l.d.	<l.d.	<l.d.	<l.d.	2.2	7.9	12.6	15.8	17.1	21.4
14CO2	A	n.p.	n.p.	<0.1	<0.1	<0.1	0.5	1	2	3	3.7
	B	n.p.	n.p.	<0.1	<0.1	<0.1	0.6	1.4	2.6	3.5	3.5
	Mean	n.p.	n.p.	<0.1	<l.d.	0.1	0.6	1.2	2.3	3.2	3.6

 

l.d.: limit of detection
A/B: Replicates
100 % corresponds to 1.047 mg parent equivalents/I
1 Corresponding to Tokyo, Japan (35°N latitude) spring sunlight
2 natural summer sunlight at latitude 30 to 50°N

Table 5. Degradation of 14C-labelled test substance in the dark control samples. Results are shown in % of the applied radioactivity.

Dark Control Pond Water Pattern
(% applied)	Incubation Time in days
	0	1	3	5	7	11	15
Test substance	100	96.8	91.1	91.5	84.5	83.2	76.3
Unknown 3	<0.1	<0.1	1.9	3	4.2	7.3	8.2
M1	<0.1	<l.d.	2.2	1.7	2.5	3.4	3.4
Unknown 11	<0.1	<l.d.	0.6	0.5	<l.d.	<l.d.	<l.d.
TOTAL	100	96.8	95.8	96.7	91.1	94	88

A/B: Replicates
l.d.: limit of detection
100 % corresponds to 0.948 mg parent equivalents/I
Note: The backwash from the samples represented only the parent compound. It should be noted that the parent compound was completely photo-degraded within in the irradiated sample less than 17 days.

Table 6. Comparison of the major metabolites detected by HPLC and 2D/1D-TLC.

		HPLC	2D-TLC
Interval	Name of fraction	(% applied)	(%applied)
	Test substance	100	99.5
	M1	<l.d.	<l.d.
Day0 A	Unknown 5	<l.d.	<l.d.
	Unknown 11	<l.d.	<l.d.
	Unknown 12	<l.d.	<l.d.
	Test substance	4.9	7.7
	M1	75.6	71.4
1hour B	Unknown 5	<l.d.	<l.d.
	Unknown 11	<l.d.	<l.d.
	Unknown 12	<l.d.	<l.d.
Day 15 A	Test substance	<l.d.	0.8
	M1	2.6	2.4
	Unknown 5	15.2	6.1
	Unknown 11	31.8
	Unknown 12	17.9	59.11
			1D-TLC^2
	Test substance	<l.d.	<l.d.
	M1	2.6	4.8
Day 15 A	Unknown 5	15.2	14.6
	Unknown 11a	31.8	20.3
	Unknown 12	17.9	14.3
	Unknown 11b^3	n.d.	12.8

l.d. limit of detection
n.d. not detected
1 Unknown 11a+b and unknown 12 were not resolved by 2D-TLC
2 1D-TLC was developed two times in SS17 and thereafter in SS16
3 unknown 13 was only detected by 1D-TLC. It co-eluted with unknown 11 by HPLC

Table 7. Values used for kinetic fitting

Test substance		M1
Incubation day	Value	Incubation day	Value
	[% applied of radioactivity]		[% applied of radioactivity]
0	100	0	0
0.02	25.9	0.02	57.7
0.04	6	0.04	76.4
0.17	0	0.17	78.5
--	--	1	60.7
--	--	3	30
--	--	5	15.7
--	--	7	10.7
--	--	10	5.2
--	--	15	3
Results
Test substance		M1
Half-life	0.01d	2.1d
co	100.04	82.9229
k1	68.119	61.43676
k2	--	0.32306
f	1	0.99787

-- not applicable

Validity criteria fulfilled:

yes

Conclusions:

The 14C-labelled test substance is instantly photo-degraded in natural pond water with a photolytic Suntest half-life of about 14.4 min (0.01 days), equivalent to 0.07 days Tokyo spring sunlight (35°N) or 0.02 days summer sunlight at latitudes 30-50°N. Under irradiation, it degraded mainly by loss of its thiophosphoric acid moiety.

Executive summary:

The direct photodegradation of the test substance was determined in a study according to JMAFF Agchem Test Guidelines 12 Nousan N and a proposal of new OECD Guideline: Phototransformation of Chemicals in Water and was in compliance with GLP criteria. In this study, radiolabelled test substance was exposed to simulated sunlight in sterile natural pond water at about pH 8.5. The "Suntest" apparatus was equipped with a 1.8 kW xenon arc lamp. Filters were used to cut off ultraviolet light with a wavelength below 290 nm. For a representative range (300 nm to 400 nm) of the whole visual light spectrum, the intensity of the light was determined to be 56.5 W/m2 at the surface of the photo-degradation vessels. This intensity was slightly lower than that of natural summer sunlight at latitudes 30 to 50 °N (67.1 W/m2). Individual samples (85 mL) at an initial concentration of 1.1 mg 14C-labelled test substance/L sterile pond water were prepared. Samples were continuously irradiated for a period of 15 days at a mean temperature of 24.9 ± 0.3 °C. Duplicate irradiated samples were taken for analysis at evenly spaced intervals over the incubation period. Corresponding single control samples were incubated at a temperature of 25.3 ± 0.3 °C in the dark and taken at the same intervals as the irradiated samples. The 15 days of continuous Suntest irradiation corresponded to 109 days of natural Tokyo spring sunlight (35°N) and to 34 natural summer sunlight days at latitudes 30 to 50 °N.
The total mean recoveries from the irradiated and dark control solutions during the 15-day incubation period amounted to 98.0% ± 2.4% and 95.2% ± 3.1% of the initially applied radioactivity, respectively. The 14C-labelled test substance was rapidly photodegraded in sterile natural pond water. Within 0.04 days (1 h) of irradiation, the test item decreased from 100.0% initially to 6.0% of the applied radioactivity (mean values) and was no longer detected after this time. Besides 14C-labelled test substance, up to twelve radioactive fractions were detected in the irradiated samples of which five exceeded 10% of the applied radioactivity. The most significant photodegradation product was M1, identified by co-chromatography using HPLC and 2D-TLC. It reached its maximum amount of 78.5% after 4 hours (0.17 days) and decreased to 3.0% by the end of irradiation. The parent compound was shown to be stable in the dark for at least 1 day. Therefore the degradation in the irradiated samples was due to photolysis only. Based on the findings, the radiolabelled test substance is instantly photo-degraded in natural pond water with a photolytic Suntest half-life of about 14.4 min (0.01 days), equivalent to 0.07 days Tokyo spring sunlight (35°N) or 0.02 days summer sunlight at latitudes 30-50°N.

Description of key information

All available data were assessed and the results from the most representative study are selected for the CSA.

Nature pond water, DT50 = 0.07 d, 25 °C, JMAFF Agchem Test guideline 12 Nousan N and a proposal of new OECD Guideline: Phototransformation of Chemicals in Water, direct and indirect photolysis, Adam 2005

Key value for chemical safety assessment

Half-life in water:

0.07 d