1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole

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:

03 Mar 2004 to 04 Jun 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Study type:

direct photolysis

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

November 24, 2000 revised 26th June 2001

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Draft, August 2000

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical method:

high-performance liquid chromatography

mass spectrometry

other:

Details on sampling:

Sampling of Irradiated Samples
Duplicate vessels (one 14C-phenyl-labelled and one 14C-triazole-labelled) were analysed immediately after treatment to act as zero time samples.
Duplicate samples (one 14C-phenyl-labelled and one 14C-triazole-labelled) were removed from the Suntest instrument after 1, 3, 7, 10, 15 and 23 days of continuous irradiation.
All vessels were transferred back to the laboratory and analysed immediately.

Light source:

Xenon lamp

Details on light source:

The emission spectrum produced is closely equivalent to the global radiation of natural sunlight. A system of special mirrors and filters removes infrared radiation.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test apparatus/vessels: Vessels with side arms were used for this study in order to trap volatiles. Each vessel was individually covered with a quartz glass lid, which is suitable for general optical applications requiring good transmission in the near ultraviolet and visible range.
- Photolysis tank: Treated samples in photolysis vessels were placed in a stainless steel tank, which was designed to enable cooling water to circulate through its base in order to maintain the temperature of the vessels at ca 25°C.
- Control group: Two samples were sealed, wrapped in aluminium foil and maintained in an Environmental Test Chamber (at 25°C ± 2°C) for up to 23 days.
- Irradiation: The irradiation was conducted in two phases, i.e. the early sampling points (0 – 7 days of continuous irradiation) and later sampling points (10 - 23 days of continuous irradiation).
- Details on temperature control: To monitor the temperature of the water, a thermocouple was placed in an untreated sample and positioned in the tank alongside the treated samples. A thermometer was connected to the thermocouple to take the temperature measurements during the photolysis period.
- Details of traps for volatile: Volatile products were trapped using a sealed system. The air was pulled through the vessels using a peristaltic pump and then through a series of outlet traps. The
outlet “traps” are shown in Table 1 in ‘Any other information on meterials and methods incl. tables’. At each sampling interval the traps were removed, quantified by LSC and replaced with fresh traps. The cumulative total level of radioactivity evolved from each vessel was then calculated.
- Sterilisation method: The photolysis vessels, tubing, in-line microbial filters (for maintenance of sterility during incubation) and the buffer solution were sterilised by autoclave. All pipette tips were soaked in an ethanol/water mixture (70:30 v/v). Application was conducted in a Microbiological Class II Safety Cabinet, which was washed with ethanol/water (70:30 v/v) prior to use.

TEST MEDIUM
- Volume used/treatment: 8 mL
- Source of natural water: Middle Row Pond, Nr. Mansfield, Nottinghamshire, UK. The water was sterilised by gamma (25-40 kGy) irradiation prior to use. Water pH is 7.
- Preparation of test medium: 100 mL aliquots of the gamma-irradiated natural water were transferred into sterile glass bottles (one for the14C-phenyl treatment solution and one for the
14C-triazole treatment solution). The radiolabelled test substance solutions were dissolved in
acetonitrile to produce stock solutions (5 mL). These solutions were quantied by LSC and the volume required for preparation of each treatment solution determined. An appropriate volume of each radioactive stock solution was then added to the natural water, such that the final test substance concentration in each was 1 µg/mL.
- Concentration of co-solvent: The percentage co-solvent in each treatment solution was < 0.5%.

REPLICATION
- No. of replicates (dark): 2
- No. of replicates (irradiated): 2

Duration:

23 d

Temp.:

25 °C

Initial conc. measured:

1 mg/L

Reference substance:

not specified

Dark controls:

yes

Test performance:

- Radiochemical Purity: The radiochemical purity, of each treatment solution, was measured both before and after application. In each case the purity was > 99%.

- Application Rate: For both applications, the amount of 14C-test substance applied to each photolysis vessel was equivalent to 1.0 µg/mL. Homogeneity checks confirmed that the treatment solutions remained homogenous throughout the application periods.

- Light Intensity Measurements: Intensity measurements were taken at the beginning and end of each irradiation period. The average intensity was calculated from the two measurements. These intensities were then used to convert the irradiation periods for each sampling interval from hours of continuous irradiation to days of summer sunlight at 30, 40 and 50°N and days of Tokyo spring sunlight. The DT50 was then estimated under each set of natural sunlight conditions.

- Temperature Measurements: The mean temperature of the irradiated samples was 25.1 °C (standard deviation of 1.0 °C). The mean temperature for the dark control samples was 24.9 °C (standard deviation of 0.1 °C).

- Sterility of Test System: No significant difference in microbial growth was observed between the agar plates treated with the irradiated samples and the control plates, indicating that the samples were sterile at the end of the irradiation period.
Microbial contamination was observed in the initial check for Application B (10 - 23 DAT). However, this contamination was not observed in the final check (after 23 days irradiation). It was, therefore, possible that the sterility of the water sample used in Application B had been compromised. However, irradiation appeared to have re-sterilised the water (exposure to UV irradiation is a common method of sterilisation employed in water treatment processes). The lack of degradation observed in the dark control samples supports this hypothesis and indicated that this temporary lack of sterility did not affect the results of the study.

% Degr.:

74.2

Sampling time:

23 d

Test condition:

Irradiated

Remarks on result:

other: Triazole labelled test substance only

% Degr.:

40.2

Sampling time:

15 d

Test condition:

Irradiated

Remarks on result:

other: Phenyl labelled test substance only; samples from day 23 are considered to be not valid

% Degr.:

0

Sampling time:

23 d

Test condition:

Dark control

Remarks on result:

other: Mean of phenyl and triazole labelled test subtance

Key result

DT50:

17.5 d

Test condition:

Summer sunlight at 40 °N

DT50:

18.4 d

Test condition:

Summer sunlight at 50 °N

DT50:

18 d

Test condition:

Summer sunlight at 30 °N

DT50:

58.1 d

Test condition:

Tokyo spring sunlight

Transformation products:

yes

Remarks:

From 14C-Triazole- test substance only

No.:

#1

No.:

#2

Details on results:

An overview of the results is provided in Table 2 - Table 6 in 'Any other information on results incl. tables'

- Mass Balance: The mass balance for irradiated samples treated with 14C-phenyl labelled test substance ranged from 88.3 - 102.9% (mean 97.6%). The mass balance for irradiated samples treated with 14C-triazole labelled test substance ranged from 95.5 - 103.9% (mean 100.3%).
The mass balance for dark control samples treated with labelled test substance ranged from 100.4 - 102.7% (mean 101.6%). The mass balance for dark control samples treated with labelled test substance ranged from 98.3 - 103.8% (mean 100.7%).

- Volatile Products: Low levels of radioactivity were evolved as volatile products, which were trapped in sodium hydroxide. The maximum level of volatile components evolved from the samples treated with 14C-phenyl test substance was 9.3 % of the applied radioactivity, whereas signicantly less radioactivity was recovered from the sodium hydroxide traps for samples treated with 14C-triazole test substance (maximum of 1.4 % of applied radioactivity). The radioactivity evolved from the 14C-phenyl samples was characterised as 14CO2 by precipitation, from a representative sample, as barium carbonate followed by regeneration. For the sample tested, 90.2 % of the trapped radioactivity was characterised as 14CO2. This level of characterisation is within the experimental error inherent in the procedure used. It was therefore concluded that the entire volatile radioactivity trapped in this study was due to 14CO2.
A slight decrease in mass balance was observed with the 14C-phenyl-labelled samples (minimum recovery of 88.2% of applied radioactivity). The carboseive traps for the 10 and 15 DAT samples were, therefore, eluted with acetonitrile and the radioactivity in the eluant was quantied by LSC. No additional radioactivity was recovered from these traps.

- Photodegradation of the Test Substance: Signicant photodegradation of the test substance was observed in the study, such that only 26% of the parent compound applied remained after 23 days of continuous irradiation.
In the 14C-phenyl labelled samples, a large number of discrete degradates were observed (at least 10). None of these degradates was observed at levels of > 10% of the applied radioactivity at any point during the study and no co-chromatography with reference standards was observed.
In the 14C-triazole labelled samples, at least 12 discrete degradates were observed. Only 2 of these degradates were observed at levels of > 10% of the applied radioactivity. These were characterised by 2D-TLC co-chromatography with reference standards as M4 (maximum of 16.5% after 23 days irradiation) and M19 (maximum of 16.4% after 23 days irradiation).
No degradation was observed in the dark control samples, indicating that the degradation in irradiated samples was due to photodegradation only.

Table 2, Mass balance

Sample type	DAT	Percentage of applied radioactivity in
		Aqueous	NaOH traps	Total	Mean
14C-phenyl labelled irradiated	0	102.7	NA	102.7	97.6
	1	102.9	0.0	102.9
	3	101.5	0.0	101.5
	7	92.8	3.6	96.4
	10	84.6	3.7	88.3
	15	81.2	9.3	90.5
	23	96.7	3.9	100.6
14C-triazole labelled irradiated	0	101.6	NA	101.6	100.3
	1	101.2	0.0	101.2
	3	100.2	0.0	100.2
	7	101.5	0.8	102.3
	10	102.5	1.4	103.9
	15	95.2	0.3	95.5
	23	96.8	0.5	97.3
14C-phenyl labelled dark control	0	101.8	NA	101.8	101.6
	7	100.4	NA	100.4
	23	102.7	NA	102.7
14C-triazole labelled dark control	0	103.8	NA	103.8	100.7
	7	100.1	NA	100.1
	23	98.3	NA	98.3

 

Table 3, Photodegradation of the test substance (irradiated samples)

DAT	Label position	% Applied radioactivity in aqueous phase	Mean % Test substance	% of applied radioactivity as test substance	Mean % test substance remaining
0	Phenyl	102.7	99.9	102.6	101.8
	Triazole	101.6	99.3	100.9
1	Phenyl	102.9	99.6	102.5	101.3
	Triazole	101.2	98.8	100.0
3	Phenyl	101.5	98.7	100.2	97.5
	Triazole	100.2	94.6	94.8
7	Phenyl	92.8	85.8	79.6	87.5
	Triazole	101.5	93.9	95.3
10	Phenyl	88.3	74.1	65.4	68.2
	Triazole	103.9	68.3	71.0
15	Phenyl	81.2	73.6	59.8	50.4
	Triazole	95.2	43.0	40.9
23	Phenyl	96.7	88.4	85.5 a.	25.8
	Triazole	96.8	26.7	25.8

a. Due to the extreme variation between the two replicates at this final time-point and the deviation of the phenyl sample from first order kinetics, the results from this sample were considered to be spurious and were not included in the mean (and, hence, the DT50 estimation).

 

Table 4, Photodegradation of the test substance (dark controls)

DAT	Label position	% Applied radioactivity in aqueous phase	Mean % Test substance	% of applied radioactivity as test substance	Mean % test substance remaining
0	Phenyl	101.8	99.8	101.6	102.2
	Triazole	103.8	98.9	102.7
7	Phenyl	100.4	99.5	99.9	99.7
	Triazole	100.1	99.3	99.4
23	Phenyl	102.7	99.8	102.5	100.3
	Triazole	98.3	99.7	98.0

 

Table 5, Photodegradates of 14C-phenyl test substance

DAT	0	1	3	7	10	15	23
% baseline	0.0	0.0	0.0	2.1	2.6	1.5	1.6
% U1	0.0	0.0	0.0	0.0	0.3	0.2	0.1
% U2	0.0	0.0	0.0	0.6	0.9	0.4	0.2
% U3	0.0	0.0	0.0	0.2	0.3	0.2	0.1
% U4	0.0	0.0	0.0	0.0	0.0	0.2	0.0
% U5	0.0	0.0	0.0	0.6	1.1	0.6	0.8
% U6	0.0	0.0	0.0	0.9	1.5	1.7	0.6
% U7	0.0	0.0	0.0	1.0	1.2	2.0	1.7
% U8	0.0	0.0	0.0	1.1	1.5	4.1	1.7
% U9	0.0	0.0	0.0	1.0	0.9	2.4	1.4
% U10	0.0	0.0	0.0	1.0	0.9	2.1	2.2

 

Table 6, Photodegradates of 14C-triazole test substance

DAT	0	1	3	7	10	15	23
% baseline	0.0	0.0	0.0	0.0	4.3	3.8	5.7
% baseline streak	0.0	0.0	1.2	1.6	1.5	0.7	1.4
% M19	0.0	0.0	1.5	1.5	8.8	10.4	16.4
% M4	0.0	0.0	2.1	1.6	8.5	15.6	16.5
% U11	0.0	0.0	0.0	0.0	1.3	0.0	1.3
% U12	0.0	0.0	0.4	0.3	1.5	2.3	2.4
% U13	0.0	0.0	0.5	0.7	3.3	2.7	3.8
% U14	0.0	0.0	0.2	0.2	0.8	0.9	0.6
% U15	0.0	0.0	0.0	0.6	0.6	0.7	0.7
% U16	0.0	0.0	0.0	0.0	1.7	1.3	1.9
% U17	0.0	0.0	0.0	0.0	0.4	0.4	0.3
% U18	0.0	0.0	0.1	0.5	1.2	1.0	1.6
% U19	0.0	0.0	0.8	1.1	1.4	1.1	0.7
% U20	0.0	0.0	0.0	0.0	0.0	0.0	1.4

 

Validity criteria fulfilled:

not specified

Conclusions:

In a photodegradation study performed in accordance with JMAFF No 8147 and OECD draft August 2000, the photolytic half-life for the test substance was calculated to be 17.5 days of summer sunlight at 40°N.

Executive summary:

The direct photodegradation of the test substance was determined in a study that was performed according to JMAFF No 8147 and OECD draft August 2000 guidelines and in compliance with GLP criteria. The photolysis of the test substance was investigated in sterile natural water. 14C-phenyl and 14C-triazole labelled test substances were applied, at a concentration of 1 µg/mL, to the sterile natural water in individual photolysis vessels. The treated solutions were continuously irradiated using light from a xenon arc lamp, which emitted light filtered to give a spectral distribution close to that of natural sunlight. The samples were maintained at 25°C ± 2°C and were irradiated for periods up to 23 days (equivalent to 30 days of summer sunlight at 30 - 50°N and 97 days Tokyo spring sunlight). Duplicate samples (one 14C-phenyl-labelled and one 14C-triazole-labelled) were analysed at 7 intervals during irradiation, including zero-time samples. Duplicate “dark control" samples were also prepared and maintained at ca 25°C for 0, 7 and 23 days, after which they were analysed.

The mean mass balance for irradiated samples treated with 14C-phenyl labelled test substance was 97.6%, of which up to 9.3 % was characterised as 14CO2. The mean mass balance for irradiated samples treated with 14C-triazole labelled test substance was 100.3%. Negligible 14CO2 (≤ 1.4 % of applied radioactivity) evolved from these samples. Degradation of the test substance followed first-order kinetics. At least 10 discrete degradates were formed in the 14C-phenyl-labelled samples, none of which represented > 10% of the applied radioactivity at any point during the study. In the 14C-triazole labelled samples, at least 12 discrete degradates were observed. Only 2 of these degradates were observed > 10% of the applied radioactivity. These were identified as M4 (maximum of 16.5% after 23 days irradiation) and M19 (maximum of 16.4% after 23 days irradiation). No degradation was apparent in the “dark controls”, indicating that the degradation in irradiated samples was due to photodegradation only. Based on the findings, the half-lives of the test substance ranged from 17.5 to 18.4 days of summer sunlight at 30 — 50°N and 58.1 days of Tokyo spring sunlight.

Description of key information

All available data was assessed. The study that calculated the half-life value of the test substance with latitude and season information was selected as the key study, while the other study is being used for supporting information.

DT50 = 17.5 days, summer sunlight at 40°N, 25 °C, JMAFF No 8147 and OECD draft August 2000, Hand & Howdle 2004

Key value for chemical safety assessment

Half-life in water:

17.5 d

Additional information

Two direct photolysis studies using a xenon lamp are available for this endpoint. Both of them are Reliability 1 studies, which followed standard test guidelines and met the GLP criteria. The study that calculated the half-life value of the test substance with latitude and season information was selected as the key study, while the other study is being used for supporting information.

In the key study (Hand and Howdle 2004), the 14C-phenyl and 14C-triazole labelled test substances at 0.1 mg/L in sterile natural water were exposed to continuous light for 23 days at 25 ˚C. The estimated half-lives ranged from 17.5 to 18.4 days of summer sunlight at 30 - 50°N and was 58.1 days of Tokyo spring sunlight. In the supporting study, the half-life of the 14C- Phenyl(U)-labelled test substance (tested at 10.8 mg/L in 0.01M phosphate buffer at pH 7) was determined to be 249 days, each day consisting of 12-hour irradiation and 12-hour darkness (Das 1990).