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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
04 June - 14 July 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
- Test material: Balsalazide acid
- Appearance: Slightly yellow brown powder
- Batch number: 0400
- Expiry date: April 2019
- Purity: >98%
- Storage: Room temperature
- Stability: 12 months
Analytical monitoring:
yes
Details on sampling:
Samples were taken from the treated vessels at the start and end of the test.
Vehicle:
no
Details on test solutions:
The test solution was sonicated for 10 minutes at room temperature to homogenise the sample.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Green alga
- Strain: SAG 61.81
- Source: laboratory

ACCLIMATION
- Culturing media and conditions: The algal suspension was kept in culture medium in sterile 250 mL Erlenmeyer flasks in the following conditions until the beginning of the test:
- Temperature: 23 ± 2°C
- Lighting: >4300 lux
- Stirring: Steady with electrical stirrer
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
23 ± 2 °C
pH:
Control: 7.80 - 8.28
Test concentration: 7.25 - 7.61
Nominal and measured concentrations:
Nominal concentration: 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks (25 and 250 mL)
- Stirring: Steady with electrical stirrer
- Initial cells density: 10^4 cells/mL
- No. of vessels per concentration: 6 replicates
- No. of vessels per control: 6 replicates

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Culture medium

OTHER TEST CONDITIONS
- Photoperiod: Continuous light
- Light intensity and quality: Fluorescent lamp - 8000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: The cells were observed at 0, 24, 48 and 72 hours using a Burker chamber.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: Ten-fold dilutions from 100 mg/L to 0.01 mg/L
- Results used to determine the conditions for the definitive study: Yes
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
A normal and healthy appearance of the algae at the end of the test was microscopically observed for the control and treated group.

The sample is considered stable because the measured concentrations of the test item at the end of the test have been maintained within ± 20% at the beginning of the test (see Table 1).

Table 1: Stability of the test item

Nominal concentration

Measured concentration (mg/L)

% concentration

Variation

Stability

T=0

T=72 h

Treated (100 mg/L)

104.3

106.2

-1.84

Stable

Table 2: Algae cell density in treated and control groups

Group

Algae density (Cells/mL; average of 6 replicates)

0 h

24 h

48 h

72 h

Control

1.0E+04

6.0E+04

1.6E+05

1.3E+06

Treated group

1.0E+04

3.8E+04

7.6E+04

5.5E+05

 

Validity criteria fulfilled:
yes
Remarks:
The cell concentration in the control cultures increased with a specific growth rate of 1.61% (average), the CVss was <35% and the CVwp was <7%
Conclusions:
According to the results of the test, the EC50 (72 hours) for algae is estimated to be >100 mg/L based on nominal concentrations of the test item “Balsalazide acid”.

Description of key information

A GLP study was performed in accordance with OECD Guideline 201 to assess the toxicity of the test material, Balsalazide acid, to algae. According to the results of the test, the EC50 (72 h) was > 100 mg/L (nominal).

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information