Ethyl [2-(4-phenoxyphenoxy)ethyl]carbamate

Phototransformation in soil

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in soil

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 Jul 1994 to 17 Jul 1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-3 (Photodegradation Studies on Soil)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical monitoring:

yes

Analytical method:

high-performance liquid chromatography

other: Thin Layer Chromatography (TLC)

Details on sampling:

- Experiment 1: Duplicate irradiated and non-irradiated samples were pulled from their respective incubation chambers on Hours 0 and 6 and Days 1, 2, 3, 7,14, 21 (one irradiated sample), and 30. During the irradiated incubation, water from the water bath leaked into one of the sample vials. Due to the limited space in the water bath, no additional samples were incubated. Consequently only one Day 21 irradiated sample was harvested.

- Experiment 2: Duplicate irradiated and non-irradiated samples were pulled from their respective incubation chambers on Hours 0, 3, 6, and 9 and Days 1, 3, 7, 14, 21, 22 (irradiated samples only) and 30. Due to the observed degradation rate an additional sampling point was added for the irradiated samples. Consequently Day 22 irradiated was harvested but no non-irradiated samples were harvested.

- Sample storage: All samples were stored after harvest in Special Studies Unit II freezer which was maintained below -5°C. The freezer was monitored by the Environmental Temperature Monitoring Computer System (EMTCS). A copy of all the temperature records is maintained in the freezer logbook. Some samples were stored temporarily in a refrigerator maintained at approximately 0°C.

Details on soil:

- Collection: The soil was harvested on December 3, 1993 from Buckeystown, Frederick County, Maryland.
- Pre-treatment: The soil was sieved through a 2 mm sieve then stored at approximately 5°C until needed for shipment. Just prior to shipment, the entire soil collection was mixed to obtain uniform moisture. The soil was shipped to the test facility on June 6, 1994 and arrived on June 14, 1994. The soil was immediately placed in a flower pot with a 3 - 4 inch soil depth to allow for air circulation and drainage then was stored in the constant temperature room at 25 ± 1˚C.
- Moisture: The soil moisture was adjusted on June 22, 1994 based on the results reported in an draft report. There was no change between the final and the draft report.
- Storage: The soil was stored in the constant temperature room for incubation at/near 75% of Field Moisture Capacity (FMC) at 25 ˚C until needed for dosing.

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

>= 290

Details on light source:

The light source was a xenon arc lamp (1.8 kW) equipped with a quartz glass dish with a selective reflecting coating and a UV glass filter. These filters and the Pyrex plate absorb wavelengths below 290 nm to simulate natural sunlight. The samples were irradiated for 12 hours per day.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test apparatus: Teflon coated septum
- Type of test system: Closed (tightly capped with an open top cap)
- Application procedure:
> Experiment 1: The soil was removed from the constant temperature room on August 10, 1994. The soil was weighed in the 2 L flask to compare to the previous weight of the soil at 75% of FMC at 1/3 bar in the 2 L flask. The soil moisture did not need to be adjusted since the second weight measurement was within 0.1 g of the first weight measurement. The lab bench was lined with aluminum foil and sprayed with a 3:1 ethanol:water solution to sterilize the area. All sample vials, glassware and any utensils needed for dosing were sterilized using an AMSCO Eagle sterilizer. Each sample vial was rectangular in shape (approximately 2.5 x 2.5 x 5.5 cm) and made of type 1 borosilicate glass with an open top cap and Teflon coated septum. Each sample vial was weighed and approximately 7 g of previously sieved (2.0 mm sieve) soil was added to each vial. Seven grams of soil was chosen to provide a 2 - 3 mm soil depth when the vial was laid on its side and to allow for maximum irradiation. When all vials were filled with soil, the vials were laid on their side. The vials were shaken slightly to produce an even layer of soil. The soil was slightly pressed with a spatula to evenly distribute the soil without packing the soil layer. The dose solution was radioassayed to determine the exact volume of dose solution needed to equal approximately 372,918 dpm (0.123 ppm). The dose solution (90 = 379,454 dpm) was dripped in a random fashion over the soil surface. The weight of the vial, and vial containing the moist soil were recorded to calculate any moisture lost during incubation and to calculate the dpm per gram of applied radiolabel. The samples were then placed in the appropriate incubation chamber.
> Experiment 2: A moisture analysis was conducted on the soil remaining from Experiment 2. The soil was transferred to a 1 L flask; the soil moisture was analysed and adjusted on August 25, 1994 for incubation prior to dosing on August 30, 1994. The soil was removed from the constant temperature room after 5 days and weighed as for Experiment 2. The soil did not need adjusting again prior to dosing since the first and second weight measurements were within 0.28 g of each other. Approximately 7 g of soil was weighed into each sample Vial as in Experiment 2. The dose solution was radioassayed to determine the exact volume of solution needed to equal approximately 372,918 dpm. The dose solution (85 µL= 372,073 dpm) was dripped in a random fashion over the soil surface. Each soil sample was vortexed for approximately 30 seconds to insure the test substance was thoroughly mixed into the soil layer. The vials were laid on their side and the soil pressed with a spatula to evenly distribute the soil. The weight of the vial, and vial containing the moist soil were recorded to calculate any moisture lost during incubation and to calculate the dpm per gram of applied radiolabel. The samples were then placed in the appropriate incubation chamber.

- Details of traps for volatile: Following Day 0, duplicate irradiated and non-irradiated samples were purged immediately after being harvested. The purge system consisted of a water aspirator pump, a manifold, three KOH (volatile) traps, a sample vial, and an open top needle. The water aspirator pump was connected to a glass manifold with multiple outlets. Most outlets were fitted with tygon tubing approximately 12 inches long and clamped to allow for optimization of the flow rate. Selected outlets were fitted with tygon tubing approximately 12 inches long with an 18 gauge needle attached to the end. The volatiles were trapped by drawing air through the sample vial into a series of KOH traps at an approximate air flow of 19 mL/min. for 30 minutes. The KOH traps consisted of three 20 mL scintillation vials, each filled with 10 mL of a 10% w/v aqueous KOH solution and sealed with an open top cap and a Teflon coated septum. These volatile traps were connected by 25 gauge stainless steel canulas, inserted from the head space of the first trap into the solution of the next consecutive trap. The 18 gauge needle from the manifold was inserted through the septum of the third consecutive KOH trap.
A gentle negative pressure was established from the water aspirator pump, then the canula of the first trap was inserted into the head space of the sample. An open-top 25 gauge needle was immediately inserted into the solution of the sample to provide air flow. Approximately 30 minutes later the canulas and needles were quickly removed from the sample vial and the KOH traps.

REPLICATION
- No. of replicates (dark): 18 (experiment 1) and 20 (experiment 2)
- No. of replicates (irradiated): 18 (experiment 1) and 20 (experiment 2)

Duration:

30 d

% Moisture:

75

Temp.:

25 °C

Initial conc. measured:

0.12 mg/kg soil d.w.

Reference substance:

not specified

Dark controls:

yes

Test performance:

1. Soil moisture was not controlled during the experiment. Moisture loss was generally low (< 5%).
2. The soil properties were not given.
3. Despite the above mentioned deviations, the results were considered sufficiently reliable.

Parameter:

not specified

% Degr.:

75.08

Sampling time:

30 d

Test condition:

Irradiated

Remarks on result:

other: Experiment 1

% Degr.:

66.73

Sampling time:

30 d

Test condition:

Dark control

Remarks on result:

other: Experiment 1

% Degr.:

76.85

Sampling time:

30 d

Test condition:

Irradiated

Remarks on result:

other: Experiment 2

% Degr.:

70.74

Sampling time:

30 d

Test condition:

Dark control

Remarks on result:

other: Experiment 2

DT50:

>= 10.4 - <= 104.3 d

Test condition:

Irradiated

Remarks on result:

other: Primary and Secondary half life; Exp.1

DT50:

>= 7.38 - <= 73.1 d

Test condition:

non-Irradiated

Remarks on result:

other: Primary and secondary half life; Exp 1

DT50:

>= 13.65 - <= 158 d

Test condition:

Irradiated

Remarks on result:

other: Primary and secondary half life; Exp 2

DT50:

>= 6.2 - <= 1 351 d

Test condition:

non-irradiated

Remarks on result:

other: Primary and secondary half life; Exp 2

Transformation products:

not specified

Remarks:

M2

Details on results:

- Volatiles: Volatiles were collected at each time point by purging through three successive traps containing 10% w/v aqueous KOH. The total percent volatiles for each sample is the sum of the percent total radiolabel for all three KOH traps. The percent volatiles reached an average of 0.25% of the total dose for Experiment 1 and 0.49% of total dose for Experiment 2.

- Radiochemical balance and PPM determination: The ppm dose rates were calculated based on the dpm applied at the time of dosing and the grams of soil per sample vial. The average dose rate was 0.125 ppm for Experiment 1 and 0.123 ppm for Experiment 2. The radiochemical balance (recovery after harvest) was based on the radioassay of the dose solution at the time of dosing versus the radioassay of the volatiles, extracted samples and residues following harvest. Some KOH fractions were assayed resulting in a less than MQA value (Minimum Quantifiable Amount, for example < MQA) generated by Talisman. These values were not included in the radiochemical balance calculation. The radiochemical balance for Experiment 1 ranged from 90.62% - 111.00% and 96.12% - 113.52% for Experiment 2

- TLC results: One dimensional TLC of the Extract 1 and Extract 2 fractions were used to qualitatively and quantitatively assay the samples from each time point. The amount of material assayed for Extraction 1 samples by one dimensional TLC was approximately 10,000 dpm. Some samples were also analysed by two dimensional TLC for profile comparison. A lesser dpm was applied to TLC plates for Extract 2 samples since this procedure coextracted a large amount of non-radiolabelled material which would have interfered with the chromatography. One TLC plate contained six samples. The lanes in this plate developed slanted but were still well defined. Some samples were repeated for TLC analysis due to either poor concentration recovery (< 80%) or poor TLC recovery (< 90%). One Extract 2 sample containing a high percent of total radiolabel was developed in the two dimensional system for Extraction 1 samples to verify that there was no crossover of components between Extraction 1 and Extraction 2 with the possible exception of origin material. There are no unique components to this soil photolysis study that were not observed in the soil metabolism study. When some of the TLC plates were scraped and quantitated, Talisman generated "less than“ MQA (Minimal Quantifiable values for several minor components. In these cases, less than MQA “(< MQA)” was listed rather than the MQA value.

- Rate constant and half-life: The primary and secondary half-lives for Experiment 1 irradiated incubation, was 10.4 days and 104.3 days, respectively, versus 7.38 days and 73.1 days for the non-irradiated incubation. The primary and secondary half-lives for Experiment 2 irradiated incubation was 13.65 days and 158 days, respectively, versus 6.2 days and 1351 days for non-irradiated incubation. The presence of biphasic kinetics tend to produce a greater variation in the half-life calculation. It appeared that the rapid primary degradation occurs within 6 - 14 days followed by a near plateau. The slow degradation due to the-secondary half-life also produces a great variation in the half-life calculation. Comparison of the half-life results seem to indicate that there is no significant difference between the irradiated and non-irradiated incubation and therefore no significant photolytic effect on soil.

- HPLC results: Most samples were analysed by HPLC for Experiment 1 to confirm the TLC results. HPLC was conducted on most of the early time points from Experiment 3, then stopped once the profile mimicked the results from Experiment 2. In each case, a reference standard was co-injected with the sample for comparison. The eluent was collected in 1 mL/min. vials. The vials were analysed by LSC analysis and a histogram was generated by Talisman computer software. Results indicate that the test substance was the major component at all time points.

- Appearance and decline of the major degradates:
In each case, the percent of total dose present in Extraction 1 slightly decreased then levelled off at approximately 80% while the Extraction 2 and residue fractions slightly increased then levelled off at approximately 10%. Volatiles were negligible (< 4.50%) in every case. In both irradiated and non-irradiated samples from both experiments, parent seems to degradate first to M2. M2 reaches up to 8% of total dose by Day 1 then quickly degradates to multiple minor components primarily seen in Extraction 2.

Characterization and identification of components
- The parent substance: The test substance was isolated from Day 14 R1 irradiated Experiment 1 sample. The sample was partitioned with chloroform. A small amount of sodium sulphate was added to the organic fraction to precipitate any remaining aqueous fraction. The sample was concentrated and analysed by two dimensional TLC. The TLC results indicated that the test substance was successfully isolated and did co-chromatograph with reference standard. In each experiment, the test substance slowly dissipates to 70 – 80% of total dose by day 30.

- General: Volatiles generally ranged from 0.2 – 0.4% and therefore were considered negligible and not further characterized. M2 reached up to 8% of total dose by Day 1 then quickly degraded to multiple minor components primarily seen in Extraction 2. With the exception of M2, component C and origin in the irradiated and nonirradiated Extraction 1 fractions of all components accounted for less than 1% of the total dose and therefore did not require further identification. Even M2 and component C usually accounted for less than 1% of the total dose therefore making further identification difficult. There were up to 7 components in Extraction 2 samples representing up to of 6.2 % total dose. These extracts were dark, slightly viscous solutions. The radiolabel was precipitated with methanol however the colour and some cellular material still coextracted with the radioactivity. It was difficult to get further characterization of any components in this fraction.
The irradiated and non-irradiated samples from both experiments were qualitatively and quantitatively equivalent. In addition, there was no significant difference observed between the irradiated and non-irradiated samples from Experiment 1 as compared to the samples from Experiment 2.
The one dimensional TLC profiles yielded qualitatively the same pattern as for the soil metabolism studies and the field dissipation study. The comparison of Day 7 replicate 1 from the soil metabolism and Day 7 replicate 2 non-irradiated indicate that there were no unique components to this soil photolysis study that were not present in the soil metabolism study. Since all the studies indicate a similar pathway, the B ring test substance soil metabolism study is being used to support the degradate identification for this study.

Table 1. Distribution of radioactivity in Experiment 1

Time	Sample	Replicate	Volitiles	Extraction 1	Extraction 2	Residue	Radiochemical balance
0 Hour	IRRAD	1	NA	105.84	2.19	2.39	110.42
0 Hour	IRRAD	2	NA	102.44	2.19	6.37	111.00
0 Hour	NON-IRRAD	1	NIA	99.13	1.84	5.35	106.32
0 Hour	NON-IRRAD	2	NA	100.56	2.21	2.83	105.60
6 Hour	IRRAD	1	0.27	95.53	4.15	2.59	102.54
6 Hour	IRRAD	2	0.31	96.08	2.71	2.99	102.09
6 Hour	NON-IRRAD	1	0.29	95.27	4.37	1.95	101.88
6 Hour	NON-IRRAD	2	0.27	96.13	2.89	3.62	102.91
Day 1	IRRAD	1	0.31	94.32	5.48	4.71	104.82
Day 1	IRRAD	2	0.27	93.71	3.93	7.12	105.03
Day 1	NON-IRRAD	1	0.26	91.55	3.98	4.24	100.03
Day 1	NON-IRRAD	2	0.28	92.26	3.92	4.82	101.28
Day 2	IRRAD	1	0.26	91.21	6.82	8.09	106.38
Day 2	IRRAD	2	0.17	87.61	5.04	7.94	100.76
Day 2	NON-IRRAD	1	0.20	90.34	4.94	10.25	105.73
Day 2	NON-IRRAD	2	0.28	85.92	4.93	8.52	99.65
Day 3	IRRAD	1	0.09	94.98	5.80	4.71	105.58
Day 3	IRRAD	2	0.33	93.73	4.56	7.31	105.93
Day 3	NON-IRRAD	1	0.20	92.98	5.76	7.28	106.22
Day 3	NON-IRRAD	2	0.32	92.66	5.99	4.63	103.60
Day 7	IRRAD	1	0.30	91.47	5.97	5.93	103.67
Day 7	IRRAD	2	0.35	85.17	8.41	14.88	108.81
Day 7	NON-IRRAD	1	0.37	90.69	7.25	4.47	102.78
Day 7	NON-IRRAD	2	0.29	78.43	10.95	13.91	103.58
Day 14	IRRAD	1	0.22	84.12	6.97	7.22	98.53
Day 14	IRRAD	2	0.27	78.44	10.48	13.68	102.87
Day 14	NON-IRRAD	1	0.27	82.02	7.71	9.16	99.16
Day 14	NON-IRRAD	2	0.11	72.53	13.71	13.90	100.25

 

Table 2. Distribution of radioactivity for experiment 2

Time	Sample	Replicate	Volitiles	Extraction 1	Extraction 2	Residue	Radiochemical balance
0 Hour	IRRAD	1	NA	106.57	1.31	5.64	113.52
0 Hour	IRRAD	2	NA	99.20	1.31	1.65	102.16
0 Hour	NON-IRRAD	1	NA	99.21	1.05	1.36	101.62
0 Hour	NON-IRRAD	2	NA	102.20	2.09	1.75	106.04
3 Hour	IRRAD	1	0.42	96.80	2.27	3.69	103.18
3 Hour	IRRAD	2	0.31	93.01	1.96	3.22	98.50
3 Hour	NON-IRRAD	1	0.36	94.49	3.66	3.39	101.90
3 Hour	NON-IRRAD	2	0.3	95.40	2.53	3.57	101.80
6 Hour	IRRAD	1	0.3	95.72	2.83	3.44	102.29
6 Hour	IRRAD	2	0.36	93.36	3.62	5.19	102.53
6 Hour	NON-IRRAD	1	0.36	97.39	2.18	4.01	103.94
6 Hour	NON-IRRAD	2	0.29	91.45	3.65	5.25	100.64
9 Hour	IRRAD	1	0.25	97.80	3.37	3.75	105.17
9 Hour	IRRAD	2	0.12	92.43	3.05	3.65	99.25
9 Hour	NON-IRRAD	1	0.17	93.78	3.17	5.05	102.17
9 Hour	NON-IRRAD	2	0.31	91.97	3.62	5.50	101.40
Day 1	IRRAD	1	0.35	91.80	4.17	6.69	103.01
Day 1	IRRAD	2	0.23	91.58	4.20	6.93	102.94
Day 1	NON-IRRAD	1	0.28	93.89	3.85	5.28	103.30
Day 1	NON-IRRAD	2	0.33	92.24	4.97	7.84	105.38
Day 3	IRRAD	1	0.42	85.86	6.08	7.88	100.24
Day 3	IRRAD	2	0.31	82.14	7.14	10.65	100.24
Day 3	NON-IRRAD	1	<MQA	83.69	6.60	9.07	99.36
Day 3	NON-IRRAD	2	0.31	78.53	8.01	12.23	99.08
Day 7	IRRAD	1	0.3	83.75	6.62	11.05	101.72
Day 7	IRRAD	2	0.18	81.87	0.62	13.45	96.12
Day 7	NON-IRRAD	1	0.07	78.65	8.85	13.10	100.67
Day 7	NON-IRRAD	2	0.26	79.23	8.51	15.03	103.03
Day 14	IRRAD	1	0.33	81.54	5.56	16.41	103.84
Day 14	IRRAD	2	0.4	76.37	5.70	18.00	100.47
Day 14	NON-IRRAD	1	0.19	73.22	5.58	20.66	99.65
Day 14	NON-IRRAD	2	0.18	77.28	5.95	18.52	101.93
Day 21	IRRAD	1	4.79	79.32	7.22	17.21	108.54
Day 21	IRRAD	2	2.05	71.17	8.36	18.71	100.29
Day 21	NON-IRRAD
Day 21	NON-IRRAD	1	1.08	75.05	8.37	16.57	101.07
		2	0.76	75.67	9.22	18.95	104.60
Day 22	IRRAD	1	1.25	75.96	9.16	16.63	103.00
Day 22	IRRAD	2	0.41	74.49	8.59	16.92	100.41
Day 30	IRRAD	1	0.45	77.32	9.76	16.33	103.86
Day 30	IRRAD	2	0.17	77.38	9.17	18.42	105.14
Day 30	NON-IRRAD	1	0.07	73.45	5.78	17.31	96.61
Day 30	NON-IRRAD	2	0.08	72.43	9.24	19.62	101.37

 

Table 3. Distribution of radioactivity in Experiment 1, extract 1 (% of total dose)

Irradiated
Time	Replicate	% dose	A	B	C	D	E	F	G1	G2	H1	H2	Origin
0 Hour	1	105.84	97.2	0.26	<MQA	<MQA	<MQA	0.17	<MQA	<MQA	<MQA	<MQA	0.31
0 Hour	2	102.44	109.06	1.2	0.19	0.34	0.18	0.04	0.07	0.01	<MQA	<MQA	0.38
6 Hour	1	95.53	83.46	0.85	0.41	0.38	0.59	0.36	0.11	0.16	0.48	0.12	2.56
6 Hour	2	96.08	84	0.85	0.28	0.27	0.32	0.34	0.15	0.14	0.28	0.21	2.78
Day 1	1	94.32	88.81	2.58	0.18	0.31	0.17	0.29	0.11	<MQA	0.25	0.06	0.57
Day 1	2	93.71	91.8	4.76	0.26	0.18	0.13	0.09	0.22	0.05	0.08	0.04	0.12
Day 2	1	91.21	87.74	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	0.54
Day 2	2	87.61	78.9	0.53	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA
Day 3	1	94.98	91.31	0.9	<MQA	<MQA	0.61	<MCA	MCA	MCA	MCA	MCA	1.74
Day 3	2	93.73	86.39	0.62	0.37	22	0.67	0.16	0.08	0.04	22	0.08	2.93
Day 7	1	91.47	83.58	0.31	0.15	0.5	0.14	0.1	0.23	0.05	<MQA	<MQA	0.17
Day 7	2	85.17	72.57	0.53	0.42	0.73	0.26	0.14	0.17	0.2	0.16	0.09	1.36
Day 14	1	84.12	n,35	0.45	26	0.82	0.34	0.21	0.07	MCA	0.4	0.18	2.33
Day 14	2	78.44	73.45	0.82	0.35	0.8	0.36	0.21	0.16	0.14	0.35	0.2	3.03
Day 21	1	77.69	65.87	0.26	0.08	0.04	0.54	0.14	0.04	0.04	0.43	0.13	2.26
Day 30	1	79.27	81.08	0.71	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	2.29
Day 30	2	75.54	69.09	0.6	0.28	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	1.81
non- Irradiated
Time	Replicate	% dose	A	B	C	D	E	F	G1	G2	H1	H2	Origin
0 Hour	1	99.13	91.52	392	0.26	35	0.19	0.13	0.25	0.06	0.07	0.07	0.67
0 Hour	2	100.56	106.47	0.51	<MQA	<MQA	0.35	<MQA	<MQA	<MQA	<MQA	<MQA	1.57
6 Hour	1	95.27	81.97	0.93	0.17	0.28	0.34	0.28	0.1	0.15	0.23	0.04	3.12
6 Hour	2	96.13	85.76	0.78	0.4	0.51	0.55	0.42	0.26	0.24	0.31	0.17	2.01
Day 1	1	91.55	79.14	1.99	0.29	0.24	0.21	0.26	0.13	<MQA	0.32	0.06	0.87
Day 1	2	92.26	73.55	8.38	2.12	0.18	0.15	0.15	0.08	<MQA	<MQA	<MQA	<MQA
Day 2	1	90.34	77.48	0.75	0.61	0.48	0.51	0.34	<MQA	0.23	0.38	MOA	2.35
Day 2	2	85.92	80	0.62	0.48	0.44	0.5	0.39	0.14	0.12	0.25	0.05	1.23
Day 3	1	92.98	80.74	0.5	0.49	0.29	0.6	22	0.18	0.11	0.56	0.25	3.18
Day 3	2	92.66	91.59	0.23	0.2	0.17	0.43	0.11	0.08	0.02	0.06	<MQA	1
Day 7	1	90.69	83.57	0.44	0.19	0.72	0.15	0.05	0.06	0.12	<MQA	0.03	0.24
Day 7	2	78.43	76.71	0.46	<MQA	<MQA	0.51	<MQA	<MQA	<MQA	<MQA	<MQA	1.61
Day 14	1	82.02	72.74	0.2	0.13	0.52	0.11	0.06	0.07	0.07	0.07	MCA	0.28
Day 14	2	72.53	72.61	0.24	0.18	0.71	0.15	0.06	0.07	0.07	0.13	0.04	1.35
Day 21	1	75.87	66.61	0.23	0.13	0.07	0.62	0.08	0.05	0.08	0.19	0.06	1.84
Day 21	2	74.41	70.59	0.3	<MQA	<MQA	0.68	<MQA	<MQA	<MQA	<MQA	<MQA	0.62
Day 30	1	73.59	67.68	2.24	0.36	0.41	1.57	0.17	0.07	0.21	0.2	0.05	0.78
Day 30	2	71.17	65.78	0.56	0.34	<MQA	<MQA	<MQA	0.18	<MQA	<MQA	<MQA	3.39

A: the test substance

B: M2

 

Table 4. Distribution of radioactivity in Experiment 2, extract 1 (% of total dose)

Irradiated
Time	Replicate	% dose	A	B	C	D	E	F	G1	G2	H1	H2	Origin
0 Hour	1	106.57	97.88	0.23	0.14	0.15	0.04	<MQA	0.06	<MQA	0.04	0.02	0.05
0 Hour	2	99.20	95.75	0.63	0.35	0.19	0.09	0.10	0.05	<MQA	0.03	0.09	0.39
3 Hour	1	96.80	92.82	0.32	0.16	0.15	0.19	<MQA	0.06	<MQA	0.03	<MQA	0.06
3 Hour	2	93.01	83.15	0.33	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	2.75
6 Hour	1	95.72	89.73	4.80	0.30	0.31	0.19	0.24	0.06	0.11	0.14	0.07	0.12
6 Hour	2	93.38	82.43	3.41	0.22	0.27	0.10	0.17	<MQA	0.03	<MQA	<MQA	0.04
9 Hour	1	97.80	88.31	0.53	0.42	0.64	0.44	0.38	0.28	0.20	0.59	0.17	3.41
9 Hour	2	92.43	84.94	0.90	0.34	0.55	0.33	0.30	0.16	0.18	0.48	0.11	6.04
Day 1	1	91.80	83.77	0.40	0.06	0.03	0.30	<MQA	<MQA	<MQA	0.07	<MQA	0.20
Day 1	2	91.58	95.79	0.77	0.31	0.55	0.36	0.35	0.15	0.19	0.27	0.11	1.87
Day 3	1	85.86	83.95	0.61	0.20	0.33	0.31	0.09	0.09	0.13	0.03	0.06	2.82
Day 3	2	82.14	69.71	0.93	0.33	0.32	0.47	0.17	0.12	0.11	0.48	0.13	5.04
Day 7	1	83.75	79.79	0.56	0.23	0.55	0.38	0.18	<MQA	0.08	0.22	0.10	2.22
Day 7	2	81.87	82.49	0.61	0.26	0.47	0.40	0.18	0.07	0.11	0.37	0.08	2.70
Day 14	1	81.54	78.29	0.26	<MQA	<MQA	0.66	<MQA	<MQA	<MQA	<MQA	<MQA	1.52
Day 14	2	76.37	74.19	0.75	0.21	0.24	0.74	0.26	<MQA	0.21	0.22	<MQA	2.53
Day 21	1	79.32	66.94	0.51	0.31	0.25	0.80	0.34	0.12	0.17	0.48	0.11	1.58
Day 21	2	71.17	67.02	0.46	0.28	0.21	0.77	0.19	0.09	0.09	0.12	0.05	0.88
Day 22	1	75.96	69.43	0.37	0.15	0.15	0.53	0.12	0.03	0.04	0.21	0.11	1.44
Day 22	2	74.49	65.48	0.37	0.11	0.10	0.36	0.06	0.01	0.02	0.10	0.01	1.42
Day 30	1	77.32	77.06	0.46	0.14	0.24	0.68	0.19	0.05	0.10	0.19	0.08	1.53
Day 30	2	77.38	76.64	0.86	0.39	0.53	0.85	0.22	0.12	0.08	0.27	0.12	1.93
non- Irradiated
Time	Replicate	% dose	A	B	C	D	E	F	G1	G2	H1	H2	Origin
0 Hour	1	99.21	100.47	0.16	0.16	0.03	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA
0 Hour	2	102.50	109.74	0.41	0.36	0.21	<MQA	0.03	0.07	<MQA	<MQA	0.04	0.50
3 Hour	1	94.49	94.23	0.19	0.11	0.24	0.12	<MQA	<MQA	0.01	0.01	<MQA	0.06
3 Hour	2	95.40	88.71	0.54	0.19	0.25	0.19	<MQA	0.10	0.06	<MQA	0.05	0.13
6 Hour	1	97.39	93.39	0.56	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	0.83
6 Hour	2	91.45	87.34	0.65	0.37	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	3.49
9 Hour	1	93.78	90.99	0.67	0.38	0.44	0.29	0.24	0.12	0.13	0.30	0.17	3.49
9 Hour	2	91.97	80.45	0.27	0.19	0.42	0.10	0.06	0.07	0.17	0.20	0.12	2.23
Day 1	1	93.89	89.20	0.88	0.40	0.60	0.35	0.29	0.09	0.12	0.27	0.17	3.71
Day 1	2	92.24	87.74	0.40	0.16	0.09	0.32	0.06	0.04	0.01	0.08	0.03	1.78
Day 3	1	83.69	69.22	0.79	0.36	0.48	0.75	0.47	0.22	0.17	0.60	0.17	3.78
Day 3	2	78.53	67.78	0.36	0.25	0.59	0.30	0.17	0.09	0.13	0.28	0.06	2.83
Day 7	1	55.27	52.60	0.46	0.14	0.33	0.19	0.12	0.07	0.08	0.30	0.07	2.69
Day 7	2	79.23	80.25	0.77	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	4.13
Day 14	1	73.22	74.11	0.34	0.21	<MQA	0.83	0.37	<MQA	<MQA	0.23	<MQA	1.78
Day 14	2	77.28	74.08	0.66	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	<MQA	2.18
Day 21	1	75.05	62.22	0.21	0.20	0.20	0.66	0.23	0.08	0.13	0.24	0.08	3.26
Day 21	2	75.67	63.37	0.58	0.38	0.17	0.77	0.18	0.12	0.13	0.17	0.08	2.35
Day 30	1	73.45	71.49	0.38	0.06	0.06	0.69	0.08	0.07	0.01	0.05	0.04	0.91
Day 30	2	72.43	69.99	0.75	0.22	0.21	0.86	0.19	0.10	0.04	0.17	0.09	1.42

A: the test substance

B: M2

Validity criteria fulfilled:

yes

Remarks:

See test performance

Conclusions:

In phototransformation in soil study that was performed in accordance with EPA 161-3 guideline, there was no difference between the dark control sample and the irradiated sample. It is concluded that the test substance is not susceptible to photodegradation on soil.

Executive summary:

The phototransformation in soil of the [phenoxyphenoxy-U-14C]- labelled test substance was investigated in 7 g portions of Buckeystown soil (2 mm sieved, thickness 2-3 mm, 75% FC) at a rate of 0.12 mg/kg. The study was performed by following EPA guideline 161 -3 and was in compliance with GLP criteria. The test substance was added dropwise to the surface without mixing (experiment 1) or with mixing (experiment 2). Treated soil was placed in borosilicate glass tubes and irradiated by a Xenon light source (equipped with UV-filter with cut-off at 290 nm). Light intensity was measured and was reported as “slightly lower than” 492 W/m2 (200-700 nm). Irradiation took place in 12-hour light-dark cycles for 30 days. Dark controls were included. Temperature in the irradiated and dark control soil was 25°C. Duplicate irradiated and dark control samples of experiment 1 were analysed on days 0, 0.25, 1, 2, 3, 7, 14, 21 and 30 post treatment. Samples of experiment 2 were analysed on 0, 3, 6 and 9 hours and 1, 3, 7, 14, 21, 22 and 30 days. Radioactivity in the extracts was determined by LSC and radioactivity in the non-extracted residues (NER) by combustion/LSC. The extracts were concentrated and analysed by normal phase TLC and HPLC.Compound identification was by co-chromatography with unlabelled reference standards.

Total recovery in irradiated and dark soil, for experiment 1 and 2, ranged from 92 to 111% AR. Extractables in irradiated and dark soil decreased from 102 - 106% AR to 80 - 87% AR at day 30. Unextractable residues in irradiated and dark soil were 10 - 19% AR at day 30 (maximum 12 - 20% AR). The results for the dark soil were not different from the irradiated soil and no differences between experiment 1 and 2 were observed. In irradiated and dark soil, The test substance degraded to 67 - 77% AR at day 30. No metabolites >10% AR were observed. Unidentified fractions (10 fractions) were ≤ 8.4% AR. These fractions occurred in irradiated and dark soil samples. The primary and secondary half-lives for Experiment 1 irradiated incubation, was calculated to be 10.4 days and 104.3 days, respectively, versus 7.38 days and 73.1 days for the non-irradiated incubation. The primary and secondary half-lives for Experiment 2 irradiated incubation was calculated to be 13.65 days and 158 days, respectively, versus 6.2 days and 1351 days for non-irradiated incubation. Comparison of the half-life results seem to indicate that there is no significant difference between the irradiated and non-irradiated incubation. Therefore, it is concluded that the test substance is not susceptible to photodegradation on soil.

Description of key information

All available data was assessed and the studies representing the worst-case effects were included as key study. Other studies are included as supporting information. The key studies are considered to be worst-case and were selected for the CSA.

The test substance is not susceptible to photodegradation on soil; EPA 161 -3; Sparrow 1995

Additional information

The phototransformation in soil of the [phenoxyphenoxy-U-14C]- labelled test substance was investigated in 7 g portions of Buckeystown soil (2 mm sieved, thickness 2-3 mm, 75% FC) at a rate of 0.12 mg/kg. The study was performed by following EPA guideline 161 -3 and was in compliance with GLP criteria. The test substance was added dropwise to the surface without mixing (experiment 1) or with mixing (experiment 2). Treated soil was placed in borosilicate glass tubes and irradiated by a Xenon light source (equipped with UV-filter with cut-off at 290 nm). Light intensity was measured and was reported as “slightly lower than” 492 W/m2 (200-700 nm). Irradiation took place in 12-hour light-dark cycles for 30 days. Dark controls were included. Temperature in the irradiated and dark control soil was 25°C. Duplicate irradiated and dark control samples of experiment 1 were analysed on days 0, 0.25, 1, 2, 3, 7, 14, 21 and 30 post treatment. Samples of experiment 2 were analysed on 0, 3, 6 and 9 hours and 1, 3, 7, 14, 21, 22 and 30 days. Radioactivity in the extracts was determined by LSC and radioactivity in the non-extracted residues (NER) by combustion/LSC. The extracts were concentrated and analysed by normal phase TLC and HPLC. Compound identification was by co-chromatography with unlabelled reference standards.

Total recovery in irradiated and dark soil, for experiment 1 and 2, ranged from 92 to 111% AR. Extractables in irradiated and dark soil decreased from 102 - 106% AR to 80 - 87% AR at day 30. Unextractable residues in irradiated and dark soil were 10 - 19% AR at day 30 (maximum 12 - 20% AR). The results for the dark soil were not different from the irradiated soil and no differences between experiment 1 and 2 were observed. In irradiated and dark soil, the test substance degraded to 67 - 77% AR at day 30. No metabolites >10% AR were observed. Unidentified fractions (10 fractions) were ≤ 8.4% AR. These fractions occurred in irradiated and dark soil samples. The primary and secondary half-lives for Experiment 1 irradiated incubation, was calculated to be 10.4 days and 104.3 days, respectively, versus 7.38 days and 73.1 days for the non-irradiated incubation. The primary and secondary half-lives for Experiment 2 irradiated incubation was calculated to be 13.65 days and 158 days, respectively, versus 6.2 days and 1351 days for non-irradiated incubation. Comparison of the half-life results seem to indicate that there is no significant difference between the irradiated and non-irradiated incubation. Therefore, it is concluded that the test substance is not susceptible to photodegradation on soil.