Naphthalene-2,6-dicarboxylic acid

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

7 March 2018 - 19 July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Batch No.of test material: 0012747069
- Expiration date of the batch: 24 January 2019
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At ambient temperature
- Stability under test conditions: stable

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Three test concentrations were measured. Samples were taken in duplicate from each test concentration.
- Sample storage conditions before analysis: Samples were stored in amber glass bottles in a freezer and shipped on dry ice to the analytical lab

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
A stock solution at a nominal loading rate of 100 mg/L was prepared. This stock solution was stirred for 10 min at ca. 1000 rpm, then ultrasonicated for 3 min and subsequently stirred for 68 hours at ambient temperature in the dark with 500 rpm. After 30 minutes without stirring, particles were observed. Thereafter, the stock solution was filtered, using a glass fibre filter. The first 0.5 L of the filtrate were discarded, visual inspection of the filtrate showed no undissolved test item particles was visible in the filtrate. The filtrate (stock solution, S2) was used to prepare the desired test item concentrations and was used immediately after preparation.

Method: OECD 2000, Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures. OECD Series on Testing and Assessment Number 23. ENV/JM/MONO(2000)6.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Raphidocelis subcapitata
- Strain: SAG 61.81
- Source: Sammlung von Algenkulturen, University of Goettingen, Germany
- Age of inoculum (at test initiation): 3 days

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.8 - 23.1°C

pH:

6.6 - 9.0

Nominal and measured concentrations:

Nominal (measured): 0, 10 (4.89), 17.7, 31.6 (13.6), 56.2, 100 (46.0) mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type: open
- Material, size, headspace, fill volume: 300 mL Glass vessel, fill volume 100 +/- 5 mL
- Aeration: no
- Initial cells density: 0.3*10^4
- Control end cells density: 89*10^4
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of the test medium was adjusted to 8.0 at the start of the test
- Photoperiod: Continous illumination
- Light intensity and quality: Econlux LED Sunstrip "daylight", intensity 90.3-96.8 µE m²s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: At start of the test, the cell numbers were determined microscopically using a counting chamber. After 24, 48 and 72 hours, the cell numbers were determined by measuring the fluorescence intensity of test solution per replicate using a fluorometer. The results were converted into biomass concentration [cells/mL] using a calibration curve.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.78
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

Potassium dichromate is tested twice a year

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 46 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

> 46 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 46 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

46 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

25.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 46 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

44.6 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

41.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

46 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

25.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): In none of the concentration levels (CO and C1-05, up to 100 mg/L), deformed and/or damaged algal cells were observed.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50: 0.952 mg/L (based on growth rate)

Reported statistics and error estimates:

The data were evaluated by the Shapiro-Wilk's Test for normal distribution, and by Levene's Test for homogeneity of variances. The Williams Multiple Sequential t-test was applied to find out whether there were significant differences between the growth of algae in the controls and the algae exposed to the test item concentration. Linear regression analyses (Logit analyses) was used to determine of the concentration/response function.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the test, the EC50 values for growth rate and yield were both above the highest test concentration of 46 mg/L (saturated solution at a loading rate of 100 mg/L)

Description of key information

EC50 and NOEC values apply both for yield and growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:

46 mg/L

EC10 or NOEC for freshwater algae:

25.8 mg/L