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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions, not GLP
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
adopted 7 June 1984
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: test substance in concentrations of 100 and 1000 mg/l were moderately stirred in algal medium for 24 h at room temperature, after this the undissolved materials were removed by sterile filtration (0.45µm), the resulting water accommodated fractions (WAFs) were used in the test
- Control: algal medium
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: 86.81. SAG
- Source: from the culture collection in Göttingen, Germany
- Method of cultivation: axenic slope culture, no further details mentioned, preculture for the test: 100 ml flask containing 50 ml of sterile algal medium (according to guideline), inoculated with cell material from axenic culture, exponentially growing culture used for the test
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Remarks on exposure duration:
2 concentrations tested: 100 and 1000 mg/l as WAF
Test temperature:
22 +/- 0.2 °C
pH:
7.7 - 8.0
Nominal and measured concentrations:
100, 1000 mg/l nominal, tested as WAFs
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 ml flasks, all-glass, with 100 ml of test medium
- Initial cells density: 1x10E4 - 2x10E4 cells/ml
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: 8500 - 9000 lux, warm white fluorescent tubes

EFFECT PARAMETERS MEASURED :
- Determination of cell concentrations: counting chamber to define the starting cell density, spectrophotometer (at 680 nm) after 24 , 48 and 72 h of exposure
- Chlorophyll measurement: no
- Other: temperature (in 1 control flask at the start and at the end of the test), pH (in 1 control flask after sterilization before the test and in all test vessels at the end of the test), observations of mis-shapen cells and cell debris after 24, 48 and 72 h of exposure
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
as water accommodated fraction
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
as water accommodated fraction
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control: yes
- Observation of abnormalities: none
- Unusual cell shape: no
Results with reference substance (positive control):
periodically conducted in the testing laboratory, no further details mentioned

Table #1: Cell concentrations after 24, 48 and 72 h of exposure

 Loading rate [mg/l]   Cell concentration (measured photometrical extinction at 680 nm) mean values         
  0 h   24 h  48 h  72 h
 Control  0.013  0.042  0.170  0.625
 100  0.013  0.047  0.168  0.643
 1000  0.013  0.054  0.178  0.608

Table #2: Average specific growth rates between 24 and 72 h

 Loading rate [mg/l]  Average specific growth rate x 0.01  Inhibition [%]  Standard deviation [%]
Control  5.618  0.0  3.1
 100  5.443  3.0  2.1
 1000  5.200  10.6  3.0
Validity criteria fulfilled:
yes
Remarks:
all values (pH, temperature) were in the accepted ranges, cell concentarion in control cultures increased more than 16 fold within 3 days
Conclusions:
The EL50 based on the growth rate is > 1000 mg/l nominal concentration, the NOEL based on the growth rate is >= 100 mg/l nominal concentration.
Executive summary:

The median growth inhibiting concentration and the no-observed effect concentration based on growth rates of Diisotridecyl adipate to the green alga Scenedesmus subspicatus were investigated over a period of 72 h. The only applied concentrations were 100 and 1000 mg/l.

3 test vessels were exposed to each test concentration.

Due to the limited water solubility of the test substance, Diisotridecyl adipate in a concentrations of 100 and 1000 mg/l, respectively, were moderately stirred in algal medium for 24 h at room temperature. After this incubation time, the undissolved materials were removed by sterile filtration. The resulting water accommodated fractions were used in the test. No analysis of the test substance concentrations was conducted.

At the loading rate of 100 mg/l no significant growth inhibition compared to the untreated controls was observed. At the loading rate of 1000 mg/l a mean growth inhibition of 10.6% compared to the untreated control was observed.

Based on the result of the study it can be concluded that the EL50 (24 -72 h) of Diisotridecyl adipate based on the growth rate is > 1000 mg/l nominal concentration and the NOEL based on the growth rate is >= 100 mg/l nominal concentration.

Description of key information

EL50(72h) > 1000 mg/L (nominal, loading rate) for growth rate of Desmodesmus subspicatus (OECD 201)


NOEL(72h) >= 100 mg/L (nominal, loading rate) for growth rate of Desmodesmus subspicatus (OECD 201)

Key value for chemical safety assessment

Additional information

Based on the result of the algae study it can be concluded that the ErL50 (24 -72 h) of diisotridecyl adipate based on the growth rate is > 1000 mg/l nominal loading rate and the NOErL based on the growth rate is ≥ 100 mg/l nominal loading rate (Häner/Panolin, 1998). The effect levels are far above the limit of water solubility of diisotridecyl adipate.