2-Naphthalenol, 1-[2-[2-ethyl-4-[2-(2-ethylphenyl)diazenyl]phenyl]diazenyl]-, ar-heptyl derivs.

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:

2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

GLP compliance:

yes

Test material

Test material information

1

Reference substance name:

Reaction products of 2-Ethylaniline with heptyl naphthalen-2-ol

Cas Number:

1401000-07-4

Molecular formula:

Not applicable (UVCB Substance)

IUPAC Name:

Reaction products of 2-Ethylaniline with heptyl naphthalen-2-ol

Test material form:

solid

Specific details on test material used for the study:

Batch number: SZBD168XV

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

Since the test item is insoluble in water, it was added to the algal medium by the means of a solvent vehicle (acetone). Therefore a solvent control (algal medium whit the same concentration of acetone used as carrier) was added in order to verify the absence of toxic effect due to the solvent; moreover a negative control (algal medium without test item) was prepared.

Test organisms

Test organisms (species):

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

Details on test organisms:

The study was performed with the unicellular, fresh-water green algae Pseudokirchneriella subcapitata strain.
The algae were cultured in a climatic chamber at 24 °C ± 2 °C under continuous uniform illumination in the range 4440 - 8880 Lux in the spectral range 400-700 nm. The culture medium was the same of the test medium; the stock cultures were weekly transferred to fresh medium and maintained in continuous shaking to ensure the necessary amount of CO2 and to keep algae in suspension. Cultures containing deformed or abnormal cells were discarded. Only exponentially growing algal cultures have been used to start the test.

Study design

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Test conditions

Test temperature:

23.8 – 24.3 °C

pH:

8.12 – 8.18 at the test start
7.20 – 7.50 at the test end

Nominal and measured concentrations:

The test concentration was chosen in accordance with the results of a no GLP pre-test (range-finding test).
Five concentrations of test item in a geometric series, differing by a constant equal to 3.2, were tested; tested concentrations were 0.01, 0.031, 0.098, 0.313 and 1.0 mg test item/L.

Details on test conditions:

The treatment vessels were identified by experiment number, group and replicate number.
All the described procedures were conducted under a laminar flow bench to ensure the sterility of the algal cultures.
For the test concentrations, for the negative control and for the solvent control, 100 mL capacity conical glass flasks capped with air permeable stoppers were used.
Three replicates for each test concentrations, six for negative control were prepared.

Since the test item is coloured, to avoid adsorption of photosynthetically active light that could limit growth of algal cultures during the exposure, the reduction of the light path by reducing the volume of test solution was adopted as recommended in the OECD 23 (2000).

At test start, 45 mL of test solutions were poured into a test flask and inoculated with algae to obtain a starting cell density of about 104 cells/mL. Two further flasks for each group were prepared from the first one transferred 15 mL of test solutions.
The algal inoculum was taken from a pre-culture, started 3 days before the beginning of the test in order to ensure that the assay was performed with exponentially growing algal population. The cell density of the inoculum was around 106 cells/mL.

The test flasks were incubated in a climatic chamber, under continuous illumination and constant shaking. The flasks were randomly distributed under the light and were replaced every day during the test.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 4

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.313 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 5

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 6

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.367 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield end-point

Effect concentrations 7

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

0.623 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield end-point

Effect concentrations 8

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.537 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield end-point

Effect concentrations 9

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.313 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield end-point

Effect concentrations 10

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield end-point

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The toxicity of test item RED 2735 was tested on Pseudokirchneriella subcapitata.

The 72-hour EC10, EC20 and EC50 with their 95% confidence limits (LCL, Lower Confidence Level and UCL, Upper Confidence Level), the NOEC and LOEC, calculated in terms of the nominal concentrations of test item, for the two end-points, are reported in the following table:

Endpoint 0 - 72 h EC10 (mg/L) 0 - 72 h EC20 (mg/L) 0 - 72 h EC50 (mg/L) 0 - 72 h NOEC (mg/L) 0 - 72 h LOEC (mg/L)
Growth rate >1.0 > 1.0 >1.0 0.313 1.0
Yield 0.367(0.090 – 0.591) 0.623(0.409 – 0.843) 1.537*(0.965 – 2.449) 0.313 1
*Effective concentration calculated by Statistical Software greater than the highest tested concentration (1.0 mg/L)

The EC50 value is higher then the maximun water solubility of the test item (< 0.1 mg/l).