2,6-dibromo-4-cyanophenyl heptanoate

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Oct - 08 Nov, 1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: EPA OPP 122-2 and 123-2

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

At test initiation (day 0) and test termination (day 14), the concentration of test substance was determined in a single sample from each of the test and control solutions. Samples analyzed at 0 hour were removed from the test solution remaining in the 500-mL volumetric flasks subsequent to division into the replicate test vessels. At test termination, the replicate exposure solutions for each treatment level and control solutions were individually composited. Samples were then removed from the composite solution of each treatment level and control for analysis.

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

A 10 mg a.i./mL primary stock solution was prepared by diluting 0.5274 g (0.5000 g a.s.) of test material in a volumetric flask to volume with 50 mL of acetone.
Secondary stock solutions with nominal concentrations of 0.38, 0.75,1.5, 3.0 and 6.0 mg a.i./mL were then prepared by diluting appropriate volumes of the 10 mg a.i./mL primary stock solution with acetone to a volume of 10 mL. Test solutions with nominal concentrations of 0.038, 0.075, 0.15, 0.30 and 0.60 mg a.i./L were prepared by diluting 50 µL of the appropriate stock solution with Hoagland's medium to a volume of 500 mL. No visible signs of undissolved test material was observed in any of the test solutions.

Test organisms (species):

Lemna gibba

Details on test organisms:

The duckweed Lemna gibba, strain G3, was obtained from the University of California and maintained in stock culture at the laboratory.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

14 d

Test temperature:

25 °C

pH:

5.1 - 6.3

Nominal and measured concentrations:

Nominal concentrations: 0.038, 0.075, 0.15, 0.30 and 0.60 mg a.i./L
Initial measured concentration: 0.041, 0.077, 0.12, 0.25 and 0.40 mg a.i./L

Details on test conditions:

Sterile 270-mL crystallizing dishes, three per treatment level and the controls, were conditioned prior to use by rinsing with the appropriate solution. 100 mL of the test solution was then placed in each of the three replicate vessels. Each test vessel was covered with an inverted, sterile, glass petri dish.
Approximately 15 minutes after the test solutions were prepared and added to the test vessels, an inoculum of five plants with three fronds each was aseptically introduced into each vessel. Test vessels were then randomly placed, based on computer-generated random numbers, on a single shelf within an environmental chamber.
The test was conducted in an environmental chamber designed to maintain the following conditions: a temperature of 25 ± 1 °C and continuous lighting with a light intensity within the range of 350 to 500 footcandles (3800 to 5400 lux).
At each 3-day interval (i.e., day 3, 6, 9 and 12) and at test termination (day 14), fronds were counted and observations were made.

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.21 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: 95 % C.I.: 0.14 - 0.31 mg a.i./L

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.077 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

biomass

frond number

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.27 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Remarks on result:

other: 95 % C.I.: 0.21 - 0.34 mg a.i./L

Details on results:

At test termination, fronds exposed to the three highest treatment levels (0.12, 0.25 and 0.40 mg a.i./L) were observed to have very little root formation and to be smaller and slightly chlorotic compared to the control.
Fronds exposed to the 0.041 and 0.077 mg a.i./L treatment levels were observed to be slightly chlorotic compared to the control.
Because of the observed decrease in test material concentration between test initiation and test termination (measured concentrations in most exposure solutions were generally -below the established limit of quantitation), the results of this test are based on initial measured concentrations.

Please refer to "overall remark/ attached background material" field for result tables.

Validity criteria fulfilled:

not specified

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the 14-day EC50 for Lemna gibba was 0.21 mg a.i./L. The NOEC was 0.077 mg a.i./L.

Description of key information

From the key study, the 14-d EC50 for aquatic plants exposed to the present test material was 0.21 mg a.i./L and 14-d NOEC 0.077 mg a.i./L in freshwater.

Key value for chemical safety assessment

EC50 for freshwater plants:

0.21 mg/L

EC10 or NOEC for freshwater plants:

0.077 mg/L

Additional information

One GLP-study is available for toxicity to aquatic plants other than algae and was identified as key study.

In key study (1993), the acute toxicity of test material to Lemna gibba was determined in a 14-day static test according to EPA OPP 122-2 and 123-2 guidelines.The 14-day ER₅₀and NOEC of the test substance were determined to be 0.21 mg a.s./L and 0.077 mg a.i./L, respectively, based on the mean initial measured concentrations.