2,6-difluorobenzamide

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-01-21 to 2003-04-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study with analytical monitoring

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2,6-difluorobenzamide

EC Number:

241-972-8

EC Name:

2,6-difluorobenzamide

Cas Number:

18063-03-1

Molecular formula:

C7H5F2NO

IUPAC Name:

2,6-difluorobenzamide

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 12.5, 50.0 and 100 mg/L (samples at test start and at test end were analyzed).

Test solutions

Vehicle:

no

Details on test solutions:

- Preparation of test solutions: The test substance was stirred in demineralized water for about 20 h at approximately 20 ± 2°C. The nominal concentration of the stock solution was 250,4 mg/2L. By diluting this stock solution with demineralized water the desired nominal concentrations were prepared.

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Green algae
- Strain: KORSHIKOV SAG 61.81
- Source: SAG (Collection of algal cultures in Göttingen, Germany)

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

23 ± 2 °C

pH:

Test start: 8.0 - 8.1
Test end: 8.7 - 8.9 (inoculated)

Nominal and measured concentrations:

Nominal concentrations: 0, 12.5, 25.0, 50.0 and 100 mg/L
Measured concentrations were within ± 5 % of the nominal values. Therefore, the results were based on nominal concentrations.

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks (nominal volume 250 ml) plugged with gas permeable silicon sponge caps
- Type (delete if not applicable): closed
- Fill volume: 100 mL
- Initial cells density: 10000
- Control end cells density: 242*10E4
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 5
- Test parameter: in vivo chlorophyll-a-fluorescence (pulsed excitation with light flashes having a wavelength of 435 nm)

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: According to guideline

OTHER TEST CONDITIONS
- Light intensity and quality: about 60 - 120 µE/(m2*s) at a wave length of 400 - 700 nm
- Illumination: Artificial light, type universal white (OSRAM L 25), permanent illumination

EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: Fluorescence was measured daily, after 72 h in a counting chamber (Neubauer improved) in replicate No. 2 of the inoculated control

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2 - 3

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 4

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

77.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 5

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 6

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes