NITTA

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

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

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

minor deviation to include use of DMF as a solvent

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Test material form:

liquid: viscous

Details on test material:

- Appearance: brown viscous liquid
- Storage conditions: room temperature in the dark

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

At the start of the test additional sacrificial vessels with dispensed test solution were taken for whole sample analysis and at the end of the test, replicate vessels of the dilution water control, solvent control and the 1.0 mg/L test concentration was taken for whole sample analysis.

Test solutions

Vehicle:

yes

Details on test solutions:

This study was run with a culture medium control, solvent control and nominal exposure concentration of 1.0 mg/L.
A primary stock concentrate of NITTA, with a nominal concentration of 10 g/L, was prepared by adding a nominal 0.1 g of test substance to 10 mL of dimethylformamide (DMF). The stock solution was used to prepare the test solution. This was achieved by the direct addition of the appropriate amount of concentrate to dilution water via a microlitre syringe into a stirring solution in a volumetric flask. The solvent control was prepared in the same way using solvent only. Test solutions were all observed to be clear and colourless. The appropriate test soluition (100 mL volume) was dispensed to each test and blank vessel.

Test organisms

Test organisms (species):

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

Details on test organisms:

Pseudokirchneriella subcapitata strain CCAP 278/4 from laboratory cultures maintained under axenic conditions. A 4-day old culture of the alga in the exponential growth phase was used as inoculum for the test. The culture was grown in the medium, and under the environmental conditions, described for the test.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test conditions

Test temperature:

Range 20.5 - 22.3°C

pH:

Range 7.06 - 7.50

Nominal and measured concentrations:

1.0 mg/L (nominal)
0.89 mg/L (mean measured concentration)

Details on test conditions:

Six replicates of the culture medium control, solvent control and a single concentration of the test substance were employed. The position of each test replicate vessel in the incubator was randomised daily. One blank vessel (without algal inoculum) was incubated concurrently for each control and the single test concentration. The algal cell densities of the inoculum and test cultures were determined by electronic particle counting, using a Coulter counter and counting between a lower and upper threshold equivalent spherical diameter of approximately 2.3 and 5.0 μm respectively. After 24, 48, and 72 hours, samples were removed from each test and blank vessel. The appropriate blank particle count was subtracted from that of the test culture to obtain the cell density.
At the end of the test microscopic observations were made on samples taken from a single replicate of the control, solvent control and the 1.0 mg/L test substance concentration.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

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 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 3

Duration:

72 h

Dose descriptor:

NOEC

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.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The EC50 for NITTA is reported to be >1 mg/L (nominal cocentration) based on growth rate and NOEC is 1 mg/L.

Executive summary:

Data available from a GLP-compliant study following OECD guideline 201, with minor deviation in that it employed the solvent DMF. Results are reported based on measured and nominal concentrations. This study is considered to be suitable for use as the key study for this endpoint. The EC50s for NITTA is reported to be >1.0 mg/L (nominal) or > 0.89 mg/L (measured; total dissolved and undissolved) based on growth rate and yield. These values are above the measure water solubilty of ca 0.3 mg/L.