Sodium bis[4-hydroxy-3-[(2-hydroxy-1-naphthyl)azo]benzenesulphonamidato(2-)]cobaltate(1-)

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:

2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: OECD guideline study; GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The test solutions were collected from each concentration and control at test initiation and completion. At test initiation, samples of the test solutions were collected from the vessels used to prepare the test solutions (bulk). At test completion, sub-samples of test solution were pooled from each of the three (or six for the control) replicates to create one sample per concentration. Approximately 40 mL of each test concentration and the control were collected in glass containers of appropriate size and stored at ambient temperature until analysis. Samples were analysed as soon after sampling as possible. Approximately 1L of control media was also collected at this time.

Vehicle:

no

Details on test solutions:

Since the Test Item was soluble in water, a stock solution was prepared at 100 mg Test Item/L and test solutions were prepared as dilutions of this stock.
To prepare the stock solution (100 mg Test Item/L), 0.2000 g ± 0.0005 g of Test Item was weighed out and rinsed into a sterile 2L glass volumetric flask containing approximately 500 mL of sterile SIS media which was then brought up to ~1000 mL with SIS media. The solution, after being stirred for approximately 30 minutes, was then topped up to the 2L mark using sterile SIS media and mixed well by inversion.
Seven test concentrations were prepared from this stock solution and tested with a laboratory control (dilution water only). The stock and test solutions were prepared in a laminar flow hood using sterile techniques.
Each pre-sterilised 250 mL test vessel was rinsed with the appropriate test solution before the ~125 mL test volume was dispensed. Three replicate test vessels of each Test Item concentration and six replicate test vessels of the laboratory control were prepared.

Test organisms (species):

Lemna minor

Details on test organisms:

Test organism species: Lemna minor
Source of test animals: Canadian Phycological Culture Centre, Waterloo, ON, Canada.
Age of inoculum at test initiation: 7 – 10 days old

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Test temperature:

24 ± 2°C

pH:

6.7 - 7.9

Salinity:

n/a

Nominal and measured concentrations:

Nominal: 1.56, 3.12, 6.25, 12.5, 25, 50, and 100 mg Test Item/L
Geo. Mean Measured: 1.36, 2.77, 5.41, 10.34, 19.80, 37.92, and 63.93 mg Test Item/L

Details on test conditions:

Test type: Static
Duration: 7 days
Test organism species: Lemna minor
Source of test animals: Canadian Phycological Culture Centre, Waterloo, ON, Canada.
Age of inoculum at test initiation: 7 – 10 days old
Test temperature: 24 ± 2 °C
Photo‐period: Continuous 24‐h light
Light intensity and quality: 85 – 135 μE/m2/s (or 6500 – 10000 lux for cool‐white fluorescent)
Control/dilution water: Synthetic growth medium; Swedish Standard (SIS)
Test vessels: 250 mL Erlenmeyer flask; sealed with foam plugs
Test volume: ~125 mL
Replicates: 3 replicates for test item concentrations and 6 replicates for the control, with a total of 9 – 12 fronds per replicate
Controls: Lab control (dilution water only)
Nominal Concentrations 1.56, 3.12, 6.25, 12.5, 25, 50, and 100 mg Test Item/L
Water quality measurements: Temperature daily in monitoring vessel; pH at beginning and end of test
Measurement Endpoints: Frond number and dry weight; EC50, LOEC, and NOEC values for yield and average specific growth rate

Reference substance (positive control):

yes

Remarks:

nickel sulphate hexahydrate

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 63.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC20

Effect conc.:

22.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC10

Effect conc.:

7.6 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 63.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC20

Effect conc.:

20.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC10

Effect conc.:

8.73 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Description of key information

There is high probability that the product is not acutely harmful to aquatic plants. 

Additional information

The toxicity of the test item was assessed in a study conducted according to OECD guideline 221 under consideration of GLP. A study according to OECD 221 was chosen because the test item is a colorant. The intensive coloration of the test solutions interfere with the growth of unicellular algae which are used in a regular OECD 201 test. For the Lemna study a stock solution at 100 mg/L was prepared. This stock was used to prepare the final test concentrations. 1.56, 3.12, 6.25, 12.5, 25, 50 and 100 mg/L were used as final test concentrations. The test was conducted as static test. After an exposure time of 7 days the EC50 for growth rate was determined to be > 63.9 mg/L based on frond number. The 7-Day EC50 for growth rate based on dry weight was > 63.9 mg/L.