ethametsulfuron-methyl (ISO); methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl)carbamoylsulfamoyl]benzoate

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: Society for Environmental Toxicology and Chemistry (SETAC), Europe, Procedures for Assessing Environmental Fate and Ecotoxicity of Pesticides (March 1995)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 002

Cas Number:

97780-06-8

Test material form:

solid

Details on test material:

Purity: 85-99%

Specific details on test material used for the study:

Phenyl(U)-14C: Radiochemical Purity: 97.0%; Specific Activity: 39.55 μCi/mg
Triazine(U)-14C: Radiochemical Purity: 96.7%; Specific Activity: 49.61 μCi/mg

Radiolabelling:

yes

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

natural sediment

Remarks:

Two sediment/water systems were used

Duration of test (contact time):

100 d

Initial test substance concentration

Initial conc.:

0.17 other: mg/kg

Based on:

act. ingr.

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: Total System - Calwich Abbey Lake

DT50:

22.8 d

Type:

other: simple first order model

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

Key result

Compartment:

other: Water Layer - Calwich Abbey Lake

DT50:

18.2 d

Type:

other: simple first order model

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

Key result

Compartment:

other: Total System - Swiss Lake

DT50:

55.6 d

Type:

other: simple first order model

Half-life of parent compound / 50% disappearance time (DT50) 4

Key result

Compartment:

other: Water Layer - Swiss Lake

DT50:

39 d

Type:

other: simple first order model

Transformation products:

yes

Remarks:

IN-A8768. IN-D7556, IN-D5119, IN-00581 and IN-B9161

Applicant's summary and conclusion

Conclusions:

Based on the results of this study, the test substance would dissipate from water-sediment systems in the environment.

Executive summary:

The aerobic biotransformation of radiolabeled test substance was studied in two different flooded sediment systems through 100 days under aerobic conditions in the dark at 20 ± 2°C. The study evaluating the aerobic degradation of the test substance in flooded sediment was conducted according to the Official Journal of the European Communities No. L 172/11, OECD Guideline 308, and SETAC Procedures for Assessing Environmental Fate and Ecotoxicity of Pesticides.

One sediment was from Calwich Abbey Lake, Calwich, Ashbourne, and was characterized as a silt loam with a pH of 7.3 and organic matter content of 8.0%. The second sediment was from Swiss Lake, Chatsworth, and was characterized as a sand with a pH of 6.6 and organic matter content of 1.8%.

The test substance degraded in the water phase and also partitioned to the sediment where it was further degraded to other metabolites that eventually were incorporated into the sediment organic fraction (NER) and slowly mineralized to CO2. Dissipation of the test substance from both the overlying water and the total water/sediment system was similarly rapid (DT50 values: 18.2-39.0 days and 22.8-55.6 days, respectively).

Up to nine metabolites were observed in the water/sediment systems. No individual unidentified product was observed that was at or approaching 5% AR during the course of the study. The major degradation product was identified to be IN-A8768. IN-D7556, IN-D5119, IN-00581 reached maximum levels between 10% and 20% AR in the total systems, while IN-B9161 reached a maximum of 8.0% AR with respect to total system. Multiple other degradate products were observed (IN-D5803, IN-N7468, IN-N7469, IN-A9795, and CO2), but at levels <5% AR.

The DT50 and DT90 values calculated from the best fit model for parent (DPX-A7881) only are summarized in the table below

SYSTEM	COMPARTMENT	DT50(DAYS)	DT90(DAYS)	χ2ERROR	R2	BESTFITMODEL
Calwich Abbey Lake	Total System	22.8	75.9	6	0.982	SFO
	Water Layer	18.2	60.4	8	0.978	SFO
Swiss Lake	Total System	55.6	184.6*	2	0.982	SFO
	Water Layer	39.0	129.6*	5	0.958	SFO

*These values are extrapolations beyond the duration of the study (100 days) 

Based on the results of this study, the test substance would dissipate from water sediment systems in the environment.