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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Refer to read across justification provided in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
< 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
direct weighing
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
Source: CAS 26399-02-0, BASF, 1995, D. subspicatus, 72 h
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtered test solution
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
Source: CAS 26399-02-0, BASF, 1995, D. subspicatus, 72 h
Details on results:
- Method 1: after 24, 48 and 72 h a turbidity was observed in combination with the appearance of bacteria.
- Method 2: after 24, 48 and 72 h bacterial growth was observed in 2 out of 3 replicates of the test concentration.

- Exponential growth in the control (for algal test): yes (initial cell number/mL: 1*10E4
Method 1: cell number/mL after 72 h: control 5.9*10E5, 100 mg/L 1.2*10E5
Method 2: cell number/mL after 72 h: control 5.9*10E5, 100 mg/L 8.3*10E5

An inhibition of the growth rate and the biomass with method 1 (unfiltered test solution) of 38.3 % and 75.1%, respectively, was observed after 72 h. With method 2 (filtered test solution) no inhibition was stated, but a biomass stimulation of 23.1 % after 72 hours .
Therefore the inhibition, observed with method 1, is not based on systemic toxicity, but can be attributed to physical effects of the undissolved particles.

The water solubility of the test substance was given as < 0.025 mg/L (column elution method).

Algal cells/mL at different concentrations:

Nominal Concentration [mg/L]

Incubation time

24 h

48 h

72 h

Control

80000

210000

590000

100 (method 1)

57000

47000

120000

100 (method 2, filtered test solution)

57000

250000

830000

Conclusions:
No toxic effects on aquatic algae were observed up to the limit of water solubility (EU method C. 3, D. subspicatus, RA CAS 26399-02-0).
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24 Oct - 27 Oct 1995
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP-Guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Principles of method if other than guideline:
With special regard to "VCI-Konzept-Entwurfes für die (akute) aquatische Prüfung von schwerlöslichen Stoffen vom 31.1.1994"
GLP compliance:
yes
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method 1: Direct weigh-in of TS; 24 h shaking in Clim-O-Shake
- Method 2: 100 mg of TS into 1 L medium, 24 h stirring with a magnetic stirrer; undissolved substance removed via glass fibre filter (pre-treatment of the filter with 1 M NaOH);
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Source: Insitute of Plant Physiology, University of Göttingen

ACCLIMATION
- Culturing media and conditions (same as test or not): same
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
23 °C
pH:
8.0 - 8.5
Nominal and measured concentrations:
Nominal: 100 mg/L
Measured:
Method 1: 0 h: 5.47 mg/L; 24 h: 3.445 mg/L; 48 h: 0.16 mg/L; 72 h: 0.055 mg/L
Method 2: 0 h: 0.045 mg/L; 24 h: <0.01 mg/L; 48 h: <0.01 mg/L; 72 h: <0.01 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 300 mL Erlenmeyer flask
- Initial cells density: 10000 cells/mL
- Control end cells density: 590000 cells/mL
- No. of vessels per concentration: 3
- No. of vessels per control: 3

GROWTH MEDIUM
- Standard medium used: yes, according to DIN 38412, mineral salt medium

OTHER TEST CONDITIONS
- Photoperiod: 24 hour permanent light
- Light intensity and quality: 300 Lux (Daylight spectrum)
- Shaking at 120 rpm

EFFECT PARAMETERS MEASURED: Cell numbers were recorded after 24, 48 and 72 h test duration.
- Determination of cell concentrations: counting chamber (Thoma chamber)
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
< 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: direct weighing in of substance
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: filtered test solution
Basis for effect:
growth rate
Details on results:
- Method 1: after 24, 48 and 72 h a turbidity was observed in combination with the appearance of bacteria.
- Method 2: after 24, 48 and 72 h bacterial growth was observed in 2 out of 3 replicates of the test concentration.

- Exponential growth in the control (for algal test): yes (initial cell number/mL: 1*10E4
Method 1: cell number/mL after 72 h: control 5.9*10E5, 100 mg/L 1.2*10E5
Method 2: cell number/mL after 72 h: control 5.9*10E5, 100 mg/L 8.3*10E5

An inhibition of the growth rate and the biomass with method 1 (unfiltered test solution) of 38.3 % and 75.1%, respectively, was observed after 72 h. With method 2 (filtered test solution) no inhibition was stated, but a biomass stimulation of 23.1 % after 72 hours .
Therefore the inhibition, observed with method 1, is not based on systemic toxicity, but can be attributed to physical effects of the undissolved particles.

The water solubility of the test substance was given as < 0.025 mg/L (column elution method).

Algal cells/mL at different concentrations:

Nominal Concentration [mg/L]

Incubation time

24 h

48 h

72 h

Control

80000

210000

590000

100 (method 1)

57000

47000

120000

100 (method 2, filtered test solution)

57000

250000

830000

Description of key information

No effects up to the limit of water solubility (EU method C. 3, D. subspicatus); read-across

Key value for chemical safety assessment

Additional information

There is no study available assessing the toxicity of the target substance Fatty acids, C16-18, isononyl esters (CAS 91031-57-1) to aquatic algae. Therefore, read-across to the structurally related source substance 2-ethylhexyl oleate (CAS 26399-02-0) was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The source substance is characterized by a similar fatty acid chain length as well as alcohol component and is therefore considered a suitable representative for the assessment of the toxicity of the target substance to aquatic algae. A detailed read-across justification is provided in IUCLID section 13.

The available study was conducted according to EU method C. 3 under consideration of the VCI concept draft for the acute testing of poorly soluble substances from 1994-01-31 and GLP. The effects of 2-ethylhexyl oleate (CAS 26399-02-0) to the freshwater algae Scenedesmus subspicatus were investigated in a 72-h static limit test. The test solutions were prepared by two different methods, i.e. by direct weigh-in (24 h shaking) with and without filtration. The testing with a nominal concentration of 100 mg/L without removal of insoluble particles resulted in a mean inhibition of the algal growth rate and biomass of 38.3% and 75.1%, respectively. No effects were observed after removal of insoluble particles (filtration of the test solution) on algal growth rate and a stimulation of biomass by 23.1 % was observed. It can be assumed that undissolved test item inhibited algal growth due to physical effects and not due to intrinsic toxicity. Therefore, an ErC50 (72 h) of > 100 mg/L can be derived, implying that no effect could be observed up to the limit of the water solubility.

Based on the structural and chemical similarity of the target and source substance, the target substance is expected to exhibit a similar ecotoxicological profile. Therefore, it can be concluded that Fatty acids, C16-18, isononyl esters (CAS 91031-57-1) will not exhibit toxic effects to aquatic algae up to the limit of water solubility.