Chlorimuron ethyl

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:

test procedure in accordance with national standard methods

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1996

Report date:

1996

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: U.S. EPA-FIFRA, 40 CFR, Part 158.540, Pesticide Assessment Guidelines Subdivision J, 123-2

Deviations:

no

GLP compliance:

yes

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

Details on test material:

Purity: 97.95%

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

yes

Remarks:

20X AAP nutrient medium

Test organisms

Test organisms (species):

other: Lemna gibba G3

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

14 d

Test conditions

Test temperature:

23.9-25.6°C

pH:

7.63-9.62

Nominal and measured concentrations:

0, 0.02, 0.07, 0.20, 0.62, 1.95 μg a.i./L

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

14 d

Dose descriptor:

other: EC25

Effect conc.:

0.18 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: Frond counts

Remarks on result:

other: 95% C.I. 0.16-0.20 μg a.i./L

Effect concentrations 2

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.27 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: Frond counts

Remarks on result:

other: 95% C.I. 0.25-0.30 μg a.i./L

Effect concentrations 3

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.07 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: Frond counts

Effect concentrations 4

Duration:

14 d

Dose descriptor:

other: EC25

Effect conc.:

0.25 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: 95% C.I. 0.16-0.31 μg a.i./L

Effect concentrations 5

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.45 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: 95% C.I. 0.36-0.66 μg a.i./L

Effect concentrations 6

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.2 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

14 d EC50: 0.27 μg a.i./L (Frond counts)
14 d NOEC: 0.07 μg a.i./L (Frond counts)
14 d EC50: 0.45 μg a.i./L (biomass)
14 d NOEC: 0.20 μg a.i./L (biomass)

Executive summary:

A study was conducted to determine the effect of the test substance on the growth and reproduction of Lemna gibba G3 according to the guideline EPA OPP 123-2. The plants were exposed to measured concentrations of 1.95, 0.62, 0.20, 0.07, and 0.02 ppb (μg active ingredient/Liter of nutrient medium).

For the definitive test, the organisms were exposed for 14 days without test medium renewal. The effect was 14 days without test medium renewal. The effect was expressed in terms of percent inhibition in frond growth and biomass relative to the blank control on day 14 of the study. The results are as follows: 14 d EC50: 0.27 ppb (growth inhibition); 14 d NOEC: 0.07 ppb (growth inhibition); 14 d EC50: 0.45 ppb (biomass); 14 d NOEC: 0.20 ppb (biomass).

Recovery was assessed for each treatment from the definitive test with 50% or greater inhibition relative to the blank control (1.95 and 0.62 ppb). The 0.20 ppb rate was included in the recovery test based on biological observations (frond size and reproduction rate) during the definitive test. The 0.07 ppb was also included for comparison. One replicate from each rate and blank (culture medium) control was randomly selected. Plants were transferred to untreated medium (20X AAP). The plants were exposed to the 20X AAP for 14 days. The effect was expressed in terms of percent inhibition in frond growth and biomass relative to the blank control on day 14 of the study. Biomass was not determined for the 1.95 ppb rate because of the low frond counts and stuntedness in frond size as compared to the blank control. The 0.62 ppb rate was included because biological observations indicated that most fronds appeared comparable in size to those of the blank control, thus indicating less inhibition due to biomass.

Following the 14-day recovery period, the growth inhibition results are as follows:

Frond counts - 1.95 ppb: 97.8% inhibition; 0.62 ppb: 92.4% inhibition; 0.20 ppb: 5.4% inhibition; 0.07 ppb 10.6% inhibition

Biomass - 1.95 ppb: Not determined due to lack of plant growth; 0.62 ppb: 86.9% inhibition; 0.20 ppb: 4.0%

inhibition; 0.07 ppb 4.7% inhibition.

The Welch's T-test indicated a statistically significant inhibition effect for both the 1.95 and 0.62 ppb rates for the recovery test. Thus, the test substance is phytotoxic to Lemna gibba G3 at concentrations greater than or equal to 0.62 ppb.

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