Bromacil

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:

key study

Study period:

January 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Bromacil

EC Number:

206-245-1

EC Name:

Bromacil

Cas Number:

314-40-9

Molecular formula:

C9H13BrN2O2

IUPAC Name:

5-bromo-3-sec-butyl-6-methylpyrimidine-2,4(1H,3H)-dione

Specific details on test material used for the study:

Purity: 97%

Sampling and analysis

Details on sampling:

The initial pH of each treatment was measured.

Test solutions

Vehicle:

yes

Details on test solutions:

Primary stock solution of 101 μg a.i./mL was prepared by weighing 10.4 mg Bromacil and diluting to 100 mL in a volumetric flask with 20X-AAP medium.
The test concentrations were prepared by quantitatively diluting aliquots of the primary stock solution with 20X-AAP medium in 1000 mL volumetric flasks.

Test organisms

Test organisms (species):

Lemna gibba

Study design

Test type:

static

Total exposure duration:

14 d

Test conditions

Test temperature:

25 °C

pH:

7.4 - 7.6

Nominal and measured concentrations:

Nominal test solution concentrations of 19.2, 38.4, 75.8, 152, 303 and 606 μg a.i./L.

Details on test conditions:

Lemna gibba was exposed to six concentrations (19.2 to 606 µg a.i./L nominal) of Bromacil.
Frond counts were made using a lighted magnifying lens. At day 14, total biomass (dry weight) was determined.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

14 d

Dose descriptor:

other: EC25

Effect conc.:

23.6 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond number

Effect concentrations 2

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

45.1 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond number

Effect concentrations 3

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

32.4 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond number

Effect concentrations 4

Key result

Duration:

14 d

Dose descriptor:

other: EC25

Effect conc.:

26 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 5

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

47.5 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 6

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

17 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The test treatments at day 0 and day 14 were analyzed for Bromacil. Population growth was determined by frond counts performed on days 2, 5, 7, 9, 12 and 14. Plant biomass (dry weight) was determined at test termination.
Results are based upon the initial measured concentrations of Bromacil, which ranged from 17 to 656 μg a.i./L (recoveries ranged from 84.4% to 110% at test initiation).
The EC25 and EC50 values were determined by weighted least squares nonlinear regression of the log of concentration against each of the growth parameters. The no observed effect concentration (NOEC) was determined by an analysis of variance and Dunnett's test on the log of the mean frond counts and on biomass at day 14.

Applicant's summary and conclusion

Conclusions:

The objective of the study was to investigate the influence of Bromacil on growth and reproduction of Lemna gibba.
The EC25 is 23.6 μg a.i./L (95% confidence limits 15.9 - 34.9 μg a.i./L) and the EC50 is 45.1 μg a.i./L (95% confidence limits 34.0 - 60.0 μg a.i./L).