Chlorimuron ethyl

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Reference 2

Reference Type:

other: Addendum to study report

Title:

Unnamed

Year:

1986

Report date:

1986

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The photodegradation of [pheny1-14c(U)] DPX-F6025 and [pyrimidine-2-14c] DPX-F6025 (ethyl 2-[[[[4-chloro-6-methoxypyrimidine-2-yl)- amino]carbonyl]amino]sulfonyl]benzoate) was examined in sterilized, buffered, aqueous solutions at pH 5, 7, and 9. The rate of degradation of DPX-F6025 in samples exposed to simulated sunlight was compared to degradation of control samples kept protected from light. The temperature of all test solutions was maintained at 25°C.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

ethyl 2-({[(4-chloro-6-methoxypyrimidin-2-yl)carbamoyl]amino}sulfonyl)benzoate

EC Number:

618-690-2

Cas Number:

90982-32-4

Molecular formula:

C15H15ClN4O6S

IUPAC Name:

ethyl 2-({[(4-chloro-6-methoxypyrimidin-2-yl)carbamoyl]amino}sulfonyl)benzoate

Test material form:

solid

Remarks:

White

Details on test material:

95 to >99% purity

Specific details on test material used for the study:

[pyrimidine-2-14c] DPX-F6025 and [phenyl-14c(U)] DPX-F6025

Radiolabelling:

yes

Study design

Oxygen conditions:

not specified

Inoculum or test system:

natural water

Duration of test (contact time):

15 d

Initial test substance concentration

Initial conc.:

5 other: ppm

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

Results and discussion

Half-life of parent compound / 50% disappearance time (DT50)

Half-life of parent compound / 50% disappearance time (DT50) 1

Key result

Compartment:

other: pH 5

DT50:

12 d

Half-life of parent compound / 50% disappearance time (DT50) 2

Key result

Compartment:

other: pH 7

DT50:

27 d

Half-life of parent compound / 50% disappearance time (DT50) 3

Key result

Compartment:

other: pH 9

DT50:

>= 31 - <= 43 d

Transformation products:

yes

Remarks:

4-chloro-6-methoxy-2-pyrimidinamine and Ethyl 2-aminosulfonylbenzoate

Any other information on results incl. tables

Addendum 1 Summary:

The unidentified photoproduct from the aqueous photolysis of the test substance (designated unknown 1 in AMR-456-85) has been identified as ethyl 2-[[[[(4-hydroxy-6-methoxypyrimidin-2-yl)amino]-carbonyl]amino]- sulfonyl] benzoate. At pH 9.0. this compound accounts for approximately 12% of the total radioactivity after 15 days of continuous exposure and is the only photoproduct comprising over 10% of the total radiolabel. The compound was isolated from a 200 ppm test substance solution photolyzed in PH 9.0 buffer in order to isolate enough material for characterization. The identity of Unknown 1 was verified by co-chromatography with an authentic reference standard and also comparison of the mass spectra and proton nuclear magnetic resonance (NMR) spectra of Unknown 1 and a synthetic reference standard.

Applicant's summary and conclusion

Validity criteria

Validity criteria fulfilled:

yes

Conclusions:

After 15 days of continuous exposure, degradation rates in the exposed samples were approximately two-fold greater than in the dark controls.

Executive summary:

The photodegradation of [pheny1-14c(U)] DPX-F6025 and [pyrimidine-2-14c] DPX-F6025 (ethyl 2-[[[[4-chloro- 6-methoxypyrimidine-2-yl)amino]carbonyl]amino]sulfonyl]benzoate) was examined in sterilized, buffered, aqueous solutions at pH 5, 7, and 9. The rate of degradation of DPX-F6025 in samples exposed to simulated sunlight was compared to degradation of control samples kept protected from light. The temperature of all test solutions was maintained at 25°C.

After 15 days of continuous exposure, test substance degradation rates in the exposed samples were approximately two-fold greater than in the dark controls. At pH 5, where significant hydrolysis of the test substance occurs, the first half-life was approximately 12 days for the exposed samples compared to 29 days for the dark controls. At pH 7, the test substance degraded with a first half-life of 27 days in the irradiated samples: because of the stability of the test substance at pH 7, the half-life for the dark controls could not be calculated. At pH 9, the most hydrolytically stable pH for the test substance, the parent degraded with a first half-life of 31-43 days of continuous exposure: as for pH 7, the half-life for the dark controls could not be determined. At least four unidentified photoproducts were formed at pH 9, the largest accounting for only about 12% of the total radiolabel after 15 days of continuous high intensity exposure; ca. 70% of the original test substance remained at the end of this exposure period. Therefore, under the conditions of these studies, although photolysis does occur, it does not appear to play a major role in the degradation of the test substance.