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

Toxicity to aquatic plants other than algae

Administrative data

Endpoint:

toxicity to aquatic plants other than algae

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:

2009

Report date:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Deviations:

yes

Remarks:

Periodic analyses of well water for potential contaminants were not performed according to GLP standards, but were performed using a certified laboratory and standard U.S. EPA analytical methods.

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II))

Deviations:

yes

Remarks:

Periodic analyses of well water for potential contaminants were not performed according to GLP standards, but were performed using a certified laboratory and standard U.S. EPA analytical methods.

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: 100%

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

yes

Remarks:

20X AAP nutrient medium

Test organisms

Test organisms (species):

Lemna gibba

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Post exposure observation period:

7 days

Test conditions

Test temperature:

24.1 to 24.7°C (exposure phase)
24.0 to 24.8°C (recovery phase)

pH:

7.9 to 9.0

Nominal and measured concentrations:

Nominal: 0.063, 0.13, 0.25, 0.50, 1.0, and 2.0 μg/L
Mean, measured: 0.0540, 0.129, 0.249, 0.510, 1.02, and 2.16 μg/L
Mean, measured: 0.510, 1.02, and 2.16 μg/L (recovery study)

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0.445 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Frond count

Remarks on result:

other: 95% confidence interval: 0.400 to 0.483 μg/L

Effect concentrations 2

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0.422 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Frond Count Yield

Remarks on result:

other: 95% Confidence Interval: 0.376 to 0.457 μg/L

Effect concentrations 3

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0.808 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Frond Count Growth Rate

Remarks on result:

other: 95% Confidence Interval: 0.726 to 0.891 μg/L

Effect concentrations 4

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0.502 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% Confidence Interval: 0.436 to 0.732 μg/L

Effect concentrations 5

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0.48 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Biomass Yield

Remarks on result:

other: 95% Confidence Interval: 0.416 to 0.553 μg/L

Effect concentrations 6

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 2.16 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Biomass Growth Rate

Effect concentrations 7

Key result

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0.129 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: frond count, frond count yield, biomass, biomass yield, growth rate (based on frond count), and growth rate (based on frond biomass)

Effect concentrations 8

Duration:

7 d

Dose descriptor:

LOEC

Effect conc.:

0.249 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: frond count, frond count yield, biomass, biomass yield, growth rate (based on frond count), and growth rate (based on frond biomass)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

7-day EC50 (geometric mean, measured, Lemna gibba G3): 0.445 μg/L (frond count)
0.422 μg/L (frond count yield)
0.502 μg/L (biomass)
0.480 μg/L (biomass yield)
0.808 μg/L (growth rate (based on frond count))
>2.16 μg/L (growth rate (based on frond biomass))

7-day NOEC (geometric mean, measured, Lemna gibba G3): 0.129 μg/L (frond count, frond count yield, biomass, biomass yield, growth rate (based on frond count), and growth rate (based on frond biomass))
7-day LOEC (geometric mean, measured, Lemna gibba G3): 0.249 μg/L (frond count, frond count yield, biomass, biomass yield, growth rate (based on frond count), and growth rate (based on frond biomass))

Executive summary:

Toxicity of the test substance to the floating freshwater vascular plant Lemna gibba G3 was determined in a static-renewal, 7-day test. The test was conducted in accordance with U.S. Environmental Protection Agency (EPA) Series 850 – Ecological Effects Test Guidelines, OPPTS Number 850.4400 and OECD Guideline 221.

The study was conducted with six concentrations of the test substance, a blank (twenty strength synthetic algal-assay-procedure nutrient medium, 20X AAP) control, and an abiotic (stability) control in an environmental chamber for 7 days at 24 ± 2°C. Four replicates were initiated for each test substance concentration and the blank control. A single test vessel containing no Lemna gibba G3 was initiated for the abiotic control. Frond counts were taken on test days 3 and 5. Frond count, biomass, and their corresponding growth rates were determined after 7 days.

Nominal test concentrations selected were 0.063, 0.13, 0.25, 0.50, 1.0, and 2.0 μg per liter. Measured the test substance concentrations were determined from samples collected from each test concentration and blank control at the beginning of the test, at test termination and on the day of test solution renewal (day 3). Geometric mean, measured concentrations were 0.0540, 0.129, 0.249, 0.510, 1.02, and 2.16 μg/L. At test conclusion, healthy frond counts increased in the blank control by at least a factor of 7 in 7 days.

The 7-day EC50 values, based on geometric mean, measured concentrations of the test substance were: frond count 0.445 μg/L, frond count yield 0.422 μg/L, biomass 0.502 μg/L, biomass yield 0.480 μg/L, growth rate (based on frond count) 0.808 μg/L, and growth rate (based on frond biomass) > 2.16 μg/L. The 7-day NOEC based on geometric mean, measured concentrations of the test substance was 0.129 μg/L for all variables.