1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2002-06-27 to 2002-12-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Official Journal of the European Communities, No l 383 A, EEC method C7;

Version / remarks:

Dec. 29, 1992

Qualifier:

according to guideline

Guideline:

other: Official Journal of the European Communities No L 194, 94/37/EC (July 29, 1994) and No L 172, 95/36/EC: Placing of the Plant Protection Products on the Market

Version / remarks:

July 14, 1995

Qualifier:

according to guideline

Guideline:

other: Society of Environmental Toxicology and Chemistry (SETAC-Europe) Procedures for Assessing the Environmental Fate and Ecotoxicity of Pesticides, Part 1, Paragraph 9: Aqueous Hydrolysis Studies

Version / remarks:

March 1995

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Remarks:

Specific activity: 4.01 MBq/mg

Analytical monitoring:

yes

Details on sampling:

Sampling times: 0, 6, 24, 48, 72, 144, 192, 240h.

Buffers:

The study was carried out with 0.01 M buffer solutions at three pH levels:
pH 5: 0.01 M acetate buffer
pH 7: 0.01 M TRIS buffer
pH 9: 0.01 M borate buffer

The water used was highly pure water, purified in a Milli-Q unit. The measured electrical conductivity was 18 MO/cm, the hardness = 0 °DH, and the TOC = 12 ppb.

Details on test conditions:

The purpose of the study was to investigate the degradation kinetics of Pencycuron and the formation and degradation as well as identity of hydrolysis products occurring at amounts > 10% of applied radio-activity at a temperature of 50ºC The test was conducted for a maximum period of 10 days.

The following study design was applicable:
duration of the test: 240h
temperature: 50 ± 0.1°C
light conditions: 24h dark

type of buffers, prepared in Milli- Q water:
pH 5: 0.01 M acetate buffer
pH 7: 0.01 TRIS buffer
pH 9: 0.01 M borate buffer

type of test vessel and content: sterile glass vials closed with crimp caps with Teflon-faced septa; 5 mL buffer

number of replicate test vessels: two for each time point

dosing of test substance: stock solution of radio-labelled test substance in ACN (0.44 mL/L dilution water) sterile 0.01 M buffer solutions

test substance concentration: 0.2 mg/L

type of measurements: sterility, pH at start and end of the test

determination of RA quantitative chemical analysis: LSC TLC

sampling times: 0, 6, 24, 48, 72, 144, 192, 240h

Duration:

240 h

pH:

5

Temp.:

50 °C

Initial conc. measured:

0.2 mg/L

Duration:

240 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.2 mg/L

Duration:

240 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

0.2 mg/L

Transformation products:

yes

Details on hydrolysis and appearance of transformation product(s):

TLC analysis showed the parent compound together with WAK5069 (THS 3995, M16 = Pencycuron-PB-Amine) as the only metabolite (> 10%). The maximum amount of metabolite was found at pH 5 reaching approximately 86% of the applied radio-activity after 10 days of hydrolysis at 50°C.

pH:

5

Temp.:

50 °C

DT50:

4.7 d

Type:

other: SFO

pH:

7

Temp.:

50 °C

DT50:

14.5 d

Type:

other: SFO

pH:

9

Temp.:

50 °C

DT50:

15.4 d

Type:

other: SFO

Details on results:

Sterile conditions were maintained during the test; the incubation temperature was maintained constant at 49.9°C and the pH values of the buffers were properly prepared and were stable at the intended values of 5.0, 7.0, and 9.0.The recoveries of the applied radioactivity varied between 97.8 and 102% at pH 5, 98.4 and 101% at pH 7, and 97.8 and 102% at pH 9, showing a complete material balance without dissipation of radio-activity from the solutions, either by volatilisation or by adsorption onto the test vessels.

The authors of the report presented first order DT50 values calculated using the linear regression tool of Microsoft Excel. The RMS estimated the SFO DT50 values according to the “Guidance document on estimating persistence and degradation kinetics from Environmental Fate studies on pesticides in EU registration” (SANCO/10058/2005 version 1.0). Calculations were based on the individual replicate measurements and employed Modelmaker 4.0. All data were given equal weight and the initial value was fitted by the model. The values recalculated by the RMS are acceptable endpoints from this study: DT50 for hydrolysis at 50°C 4.7, 14.5 and 15.4 days at pH 5, 7 and 9, respectively.

Acceptability of the test: The study is acceptable

Table 1. DT50 values in days for the hydrolysis of Pencycuron at 50°C

pH value	Calculated by the authors	DT50 value as calculated by RMS from the results
pH = 5	3.9	4.7
pH = 7	14.1	14.5
pH = 9	14.8	15.4

 

Validity criteria fulfilled:

yes

Remarks:

The study is acceptable

Executive summary:

The hydrolysis of Pencycuron was studied in 0.01 M buffer solutions, which were adjusted to pH 5, 7 and 9. The experiment was carried out in accordance with available EC and SETAC Europe Guidelines.

The test solutions were prepared with radiolabeled [methylene-14C]Pencycuron at a concentration of about 0.2 mg/L.

The solutions were incubated in the dark at 50 °C for a maximum period of 10 days under sterile conditions. The sampling intervals were 0, 6 hrs, 1, 2, 3, 6, 8 and 10 days.

The recoveries of the applied radioactivity varied between 97.8 and 102% at pH 5, 98.4 and 101% at pH 7, and 97.8 and 102% at pH 9, showing a complete material balance without dissipation of radio-activity from the solutions, either by volatilisation or by adsorption onto the test vessels.

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-06-12 to 2008-11-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Japan MAFF New Test Guideline, 12 Nousan 8147

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Qualifier:

according to guideline

Guideline:

other: EU Guidelines 94/37/EC, 95/36/EC

Qualifier:

according to guideline

Guideline:

other: US EPA Subdivision N, Section 161-1

Qualifier:

according to guideline

Guideline:

other: Canada PMRA DACO Number 8.2.3.2

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
Test 1 (Pre-test, 50°C): pH 4: 0 h, 2 h, 4 h, 6 h, 8h, 10 h, 24 h and 48 h. pH 7: 0 d, 3 d, 7 d, 9 d, 10
d, 14 d, 21 d. pH 9: 0 d, 3 d, 7 d, 9 d, 10 d, 11 d, 14 d, 21 d after treatment.
Test 2 (Main test, 25°C): pH 4: 0 h, 2.5 h (= 0.1 d), 1 d, 2 d, 3 d, 7 d, 17 d, 30 d after treatment. pH 7 /
pH 9: 0 d, 3 d, 7 d, 13 d, 20 d, 24 d, 30 d.
Test 3 (Optional test, 20°C): pH 4 / pH 7 / pH 9: 0 d, 3 d, 7 d, 14 d, 21 d, 24 d, 30 d.

- Sampling method: Two replicates were removed from the water bath at each interval for each pH and label.

- Sampling intervals/times for pH measurements: Measured at each sampling interval in each test.

- Sampling intervals/times for sterility check: At initiation of the test (day 0) and at the end of the test intervals samples were subjected to a sterility check. A small aliquot of the samples was applied onto a mixed culture medium and incubated at 30°C in the dark for at least two weeks.

- Sample storage conditions before analysis: In general, samples were analyzed on the day of sampling, except for some pH 7 and pH 9 samples. For these samples storage stability was tested over a period of 10 days. After analysis, the samples were stored in a freezer.

Buffers:

pH: 4, 7 & 9

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: The samples were dispensed into 10 mL vials, closed with crimp caps.
- Sterilisation: The buffer solutions and all glassware were sterilised before use.
- Lighting: Incubated in the dark at the required test temperature.

- No traps were used, the system was closed.

The hydrolysis of [methylene-14C]Pencycuron (designated M-label) and [phenyl-U-14C]Pencycuron (designated P-label) was studied at 50°C, 25°C and 20°C, at each temperature in buffered aqueous solutions at pH 4, 7 and 9.

Test solutions were prepared by adding aliquots (0.07 mL) of [14C]Pencycuron (M-label) or [14C]Pencycuron (Ph-label) in acetonitrile to samples (100 mL) of 0.01M buffer solutions. The buffer solutions and all glassware were sterilised before use. The concentration of the test item was 0.15 mg/L. The samples were dispensed into 10 mL vials, closed with crimp caps and incubated in the dark at the required test temperature. Duplicate samples were taken at 0 h and at 7 time points up to 48 hours (pH 4, 50°C), at 6 time points up to 21 days (pH 7 and 9, 50°C), at 7 time points up to 30 days (pH 4, 25°C), or at 6 time points up to 30 days (pH 7 and 9, 25°C; pH 4, 7 and 9, 20°C). At the designated sampling time, duplicate tubes were removed for LSC analysis and direct HPLC, with confirmation for selected samplesby TLC. The pH was checked in every sample (within 0.1 unit from target) and sterility was checked and confirmed in samples taken at the start and the end. The identity of parent compound was confirmed by HPLC-MS and HPLC-MS/MS, and that of the transformation products pencycuron-B-amine and aniline by HPLC-MS/MS and by accurate MS.

The report presented an estimation of the SFO DT50 values of the parent compound according to the “Guidance document on estimating persistence and degradation kinetics from Environmental Fate studies on pesticides in EU registration” (SANCO/10058/2005 version 1.0). Calculations were based on the individual replicate measurements and employed the model KinGUI v1.1. All data were given equal weight and the initial value was fitted by the model.

Duration:

48 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

0.15 mg/L

Remarks:

Test 1 (Pre-test)

Duration:

21 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.15 mg/L

Remarks:

Test 1 (Pre-test)

Duration:

21 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

0.15 mg/L

Remarks:

Test 1 (Pre-test)

Duration:

30 d

Temp.:

25 °C

Initial conc. measured:

0.15 mg/L

Remarks:

Test 2 (Main test) - pH 4,7 & 9.

Duration:

30 d

Temp.:

20 °C

Initial conc. measured:

0.15 mg/L

Remarks:

Test 3 (Optional) - pH 4,7 & 9.

Number of replicates:

2

Transformation products:

not measured

Remarks:

See details on results

pH:

4

Temp.:

25 °C

DT50:

19.1 d

Type:

other: SFO

Remarks on result:

other: M-label

pH:

4

Temp.:

12 °C

DT50:

63.6 d

Type:

other: SFO

Remarks on result:

other: M-label - calculated from 25°C

pH:

4

Temp.:

25 °C

DT50:

21.2 d

Type:

other: SFO

Remarks on result:

other: Ph-label

pH:

4

Temp.:

12 °C

DT50:

77.9 d

Type:

other: SFO

Remarks on result:

other: Ph-label - calculated from 25°C

pH:

7

Temp.:

25 °C

DT50:

220 d

Type:

other: SFO

Remarks on result:

other: M-label

Key result

pH:

7

Temp.:

12 °C

DT50:

732.4 d

Type:

other: SFO

Remarks on result:

other: M-label - calculated from 25°C

pH:

7

Temp.:

25 °C

DT50:

167 d

Type:

other: SFO

Remarks on result:

other: Ph-label

Key result

pH:

7

Temp.:

12 °C

DT50:

556 d

Type:

other: SFO

Remarks on result:

other: Ph-label - calculated from 25°C

pH:

7

Temp.:

20 °C

DT50:

205 d

Type:

other: SFO

Remarks on result:

other: M-label

Key result

pH:

7

Temp.:

12 °C

DT50:

435 d

Type:

other: SFO

Remarks on result:

other: M-label - calculated from 20°C

pH:

7

Temp.:

20 °C

DT50:

372 d

Type:

other: SFO

Remarks on result:

other: Ph-label

Key result

pH:

7

Temp.:

12 °C

DT50:

790 d

Type:

other: SFO

Remarks on result:

other: Ph-label - calculated from 20°C

pH:

9

Temp.:

25 °C

DT50:

263 d

Type:

other: SFO

Remarks on result:

other: M-label

pH:

9

Temp.:

12 °C

DT50:

875.6 d

Type:

other: SFO

Remarks on result:

other: M-label - calculated from 25°C

pH:

9

Temp.:

25 °C

DT50:

242 d

Type:

other: SFO

Remarks on result:

other: Ph-label

pH:

9

Temp.:

12 °C

DT50:

805.7 d

Type:

other: SFO

Remarks on result:

other: Ph-label - calculated from 25°C

Details on results:

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

Mass balances of individual samples were in the range 89-112%. The reported DT50 estimations were acceptable and the results are summarised in the Table below. Pencycuron was hydrolytically instable at pH 4 (DT50 (mean for 2 labels) 20.5 hours, 20.2 days and 29.9 days at 50°C, 25°C and 20°C, respectively). At pH 7-9, the DT50 (mean for 2 labels) was 8.2-9.1 days at 50°C, but 194-289 days at 20- 25°C. Hydrolysis resulted in near quantitative conversion of pencycuron into pencycuron-B-amine and aniline (increasing levels towards end of study). Maximum levels of pencycuron-PB-amine were 73-96% AR at 50°C (pH 4, 7 and 9), 53-71% AR at 20°C (pH 4 ) and 25°C (pH 4), 9-11% AR at 25°C (pH 7 and 9), and 6-7% AR at 20°C (pH 7 and 9). Maximum levels of aniline were 42-80% AR at 50°C (pH 4, 7 and 9), 49-64% AR at 20°C (pH 4) and 25°C (pH 4), 6-9% AR at 25°C (pH 7 and 9), and 3-4% AR at 20°C (pH 7 and 9). Other (unidentified) degradation products were at the most 4.5% AR (an artefact was produced in TRIS buffer, which, at 20°C and 25°C, was max 2.5% AR).

TRANSFORMATION PRODUCTS
Two major degradation product were formed; in the total pH range tested (pH 4 to 9) the formation of Pencycuron-PB-amine as a common hydrolysis product was observed in the label #1 Pencycuron tests and the formation of aniline as a common hydrolysis product in the label #2 Pencycuron tests. The concentration of both hydrolysis products increased towards the end of the incubations at all pH ranges tested.

Table 1: DT50 and DT90 values (days, unless indicated differently) for hydrolysis of pencycuron

Test No/Temperature (°C)	pH	Single First Order DT50 (label 1/label 2, [days])	Single First Order DT90 (label 1/label 2, [days])	Chi^2 Error
Test 1 / 50	4	17.6/23.4 hours	58.4/77.6 hours	2.6/1.9
Test 1 / 50	7	7.9/10.2	26.4/34	4.4/1.4
Test 1 / 50	9	8.4/7.9	28.1/26.2	6.3/3.4
Test 2 / 25	4	19.1/21.2	63.5/70.5	3.4/4.5
Test 2 / 25	7	220/167	733/553	1.2/1.7
Test 2 / 25	9	263/242	874/803	1.0/2.2
Test 3 / 20	4	28/31.7	92.9/105	1.5/2.3
Test 3 / 20	7	205/372	681/>1000	1.0/0.8
Test 3 / 20	9	257/254	853/844	1.0/0.9

Label #1: M-label, Label #2: Ph-label

Validity criteria fulfilled:

yes

Conclusions:

Hydrolytically instable at pH 4 (DT50 20.5 hours, 20.2 days and 29.9 days at 50, 25°C and 20°C, respectively). At pH 7-9, DT50 8.2-9.1 days at 50°C, 194-289 days at 20-25°C. Hydrolysis resulted in near quantitative conversion of pencycuron into pencycuron-B-amine and aniline (increasing levels towards end of study).

Description of key information

Converting the DT₅₀ values from the main test at 25°C at pH 7 to 12°C and taking a mean across the two radiolabels gives a DT₅₀ of 644 days at 12°C. Similarly taking values from 20°C and pH 7 and converting to 12°C gives a mean value of 612 days (at 12°C). This gives an overall mean DT₅₀ value of 628 days at 12°C for hydrolysis at pH 7. Thus, pencycuron is considered to be stable under environmental conditions.

Test Type	Result	Assessment	Reference
Hydrolysis study to OECD 111 guidelines (3 temperatures and 3 pH values)	Hydrolytically unstable at pH 4 (DT50 20.5 hours, 20.2 days and 29.9 days at 50, 25°C and 20°C, respectively). At pH 7-9, DT50 8.2-9.1 days at 50°C, 194-289 days at 20-25°C	Key study	Heinemann (2008a)
Hydrolysis in sterile buffer at 50°C to SETAC guidelines	DT50 values of 4.7, 14.5, 15.4 days at pH 5, 7 and 9, respectively at 50°C recalculated in the DAR	Supporting study	Hellpointner (2002)
Hydrolysis in sterile buffer at 25°C to EPA N-161-1 guidelines	DT50 values at pH 5 > 30 days, stable at pH 7 and 9 at 25°C	Sterility checks were not performed, calculated DT50 values were not reliable	Daly D. and D. Heim (1999)
Hydrolysis in sterile buffer at 50°C to EPA N-161-1 guidelines	DT50 values of 4.7, 14.4, 15.0 days at pH 5, 7 and 9, respectively at 50°C	EPS- This was not a laboratory study, but a recalculation of study M078742-01-1 (Hellpointner supporting study). These values provided confirmation of the endpoints derived by the RMS in the DAR.	Görlitz G. and B. Mikolasch (2003)

 

Key value for chemical safety assessment

Half-life for hydrolysis:

628 d

at the temperature of:

12 °C