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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
Study period:
from 21-01-1992 to 24-01-1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The study was performed according to an appropriate guideline and under GLP. However the study was conducted at concentrations higher than the limit of solubility of the test substance and no analytical monitoring was carried out.
Qualifier:
according to
Guideline:
other: DIN 38412 part 9
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
not specified
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: a stock solution of 0.1 g/L was stirred for 72 hours and filtered, then dilutions were prepared from the filtrate. The unfiltered nominal concentration of 10 mg/L was achieved by direct stirring of the test substance in the test medium.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: Scenedesmus subspicatus SAG 8681

- Source (laboratory, culture collection): Institute of Plant Physiology, University of Gottingen

- Age of inoculum (at test initiation): 3 days


ACCLIMATION - not reported
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
22.5-23 deg C
Nominal and measured concentrations:
Loading rate - filtered solution: 0.1, 0.3, 1.0, 3.0 and 10 mg/L
Loading rate - unfiltered solution: 0, 10 mg/L
Details on test conditions:
TEST SYSTEM

- Test vessel: Erlenmeyer flasks

- Material, size, headspace, fill volume: 300 ml  flasks, filled with 100 ml volume.

- Aeration: no

- Initial cells density:  1-10exp4 cells/ml 

- Control end cells density: 2.1 x 10^6

- No. of vessels per concentration (replicates): 3

- No. of vessels per control (replicates): 3



GROWTH MEDIUM

- Standard medium used: no

- Detailed composition if non-standard medium was used: the medium was defined as Algae 10.10 / TFB Central laboratory soil nutrients.


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: not reported

- Culture medium different from test medium: not reported

- Intervals of water quality measurement: not reported


OTHER TEST CONDITIONS

- Adjustment of pH: not reported

- Photoperiod: continuous

- Light intensity and quality: 2000 lux


EFFECT PARAMETERS MEASURED

- Determination of cell concentrations: cell numbers were determined at 24, 48, 72 and 96 h. The number of cells was determined via Thoma-Kammer method.



TEST CONCENTRATIONS

- Spacing factor for test concentrations: 3
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
EL50
Effect conc.:
> 10 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and biomass
Duration:
96 h
Dose descriptor:
EL0
Effect conc.:
0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: filtered test material
Basis for effect:
biomass
Duration:
96 h
Dose descriptor:
EL10
Effect conc.:
0.27 mg/L
Nominal / measured:
nominal
Conc. based on:
other: filtered test material
Basis for effect:
biomass
Duration:
96 h
Dose descriptor:
EL0
Effect conc.:
1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: filtered test material
Basis for effect:
growth rate
Duration:
96 h
Dose descriptor:
EL10
Effect conc.:
2.9 mg/L
Nominal / measured:
nominal
Conc. based on:
other: filtered test material
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes

- Effect concentrations exceeding solubility of substance in test medium: the test substance was measured at concentrations up to 10 mg/L, however the filtered solution reported a NOEC at concentrations at or below the limit of solubility.
Reported statistics and error estimates:
The analysis of the data was carried out in accordance with DIN regulation by a computer program by Mr. Holtmann, TFA / mathematical methods, Henkel KGaA.

Table 1. Summary of findings.

 Concentration mg/L     Cell number/ml         
 filtered  unfiltered  24 h  48 h  72 h  96 h
 0.0  -  4.7 x 10^4  3.9 x 10^5  1.2 x 10^6  2.1 x 10^6
 0.1  -  6.3 x 10^4  3.7 x 10^5  1.3 x 10^6  2.4 x 10^6
 0.3  -  3.7 x 10^4  2.9 x 10^5  9.9 x 10^5  2.0 x 10^6
 1.0  -  4.0 x 10^4  3.5 x 10^5  1.0 x 10^6  1.9 x 10^6
 3.0  -  7.3 x 10^4  4.5 x 10^5  1.3 x 10^6  2.1 x 10^6
 10  -  2.3 x 10^4  2.5 x 10^5  1.2 x 10^6  2.0 x 10^6
 -  0  4.3 x 10^4  3.0 x 10^5  1.3 x 10^  2.4 x 10^6
 -  10  0.0 x 10^0  0.0 x 10^0  0.0 x 10^0  0.0 x 10^0
Validity criteria fulfilled:
not specified
Remarks:
validity criteria was fulfilled regarding the controls' cell growth but the validity criteria for pH could not be determined as water quality was not reported.
Conclusions:
A 72 h EL50 value of >10 mg/L has been determined for the effects of the filtered test substance on growth rate of the algae S. subspicatus. The value is much higher than the limit of solubility of the test substance (ca. 0.1-0.4 mg/L), therefore the test substance is not toxic at the LoS.

Description of key information

Toxicity to aquatic algae: 96 h EL50 and EL10 >LoS (>Limit of Solubility) for the effects of the test substance on growth rate of Scenedesmus subspicatus.

Key value for chemical safety assessment

Additional information

A 96 h EL50 of >10 mg/l has been determined for the effect of tetradecanol on growth rate and biomass of Scenedesmus subspicatus (new name: Desmodesmus subspicatus), and an ErL10 of 2.9 mg/l has been determined for the effect of tetradecanol on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus), based on nominal concentrations [Henkel KGaA, 1992].

The solubility of tetradecanol is approximately 0.1-0.4 mg/l. The dose response was above the solubility, which suggests the possibility of physical fouling, and as no effects were observed on growth rate at 1 mg/l, it may be concluded that tetradecanol is not toxic at its limit of solubility.

The study reflects the lowest reliable value that is available for this endpoint.

Additionally, supporting data have been read-across from the mixture, Alcohols C14-C15 (CAS 75782-87-5):

96-h ErL50 22-46 mg/l for effects on growth rate, and NOEL 4.6 mg/l for effects on growth rate and biomass (WAF) (>LoS) of Raphidocelis subcapitata (new name: Pseudokirchneriella subcapitata) [Shell Research, 2000].

These results support the view that C14 is non-toxic at the limit of solubility.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

The data for single carbon chain length LCAAs show toxicity to increase from an ErC50 of 80 mg/L for C6 to 0.33 mg/L for C12. The C14 and C16 LCAAs were not toxic to algae, indicating a toxicity cut-off at C14 and above. Two of the studies determined NOECs that are suitable for assessing long-term toxicity. A NOEC of 11 mg/L has been reported for hexan-1-ol based on measured exposure concentrations. A test with dodecanol resulted in a 72-h EC0 (equivalent to a NOEC) value of 0.085 mg/L.

Other algal studies used a WAF methodology and/or used test concentrations greater than the limit of water solubility and/or did not report a NOEC or equivalent statistic.

The data for mixed carbon chain length LCAAs (commercial products) shows that substances containing LCAAs with carbon numbers in the ranges of C7-9 to C12-15 exerted toxicity at concentrations of between 3.1 and 0.043-0.092 mg/L. At these concentrations all the constituents are likely to have been fully dissolved. For the C12-18 and C14-15 multi-constituent substances there was evidence of toxic effects in tests conducted on water-accommodated fractions prepared at loading rates that will have exceeded the solubility of some constituents.