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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Results derived from a valid read across, with adequate and reliable documentation / justification.
Justification for type of information:
The read across justification is presented in the overall Aquatic Endpoint Summary because in that document short- and long-term toxicity to aquatic invertebrates is also included. The corresponding documentation file is also attached there.
Reason / purpose:
read-across source
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.065 mg/L
Basis for effect:
growth rate
Remarks on result:
other: Based on read across information
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.065 mg/L
Basis for effect:
growth rate
Remarks on result:
other: Based on read across information
Validity criteria fulfilled:
yes
Remarks:
Justification for read across is presented in the overall aquatic endpoint summary.
Conclusions:
For Acalea a 72-h EC50 > 0.065 mg/L and a 72-h NOEC >= 0.065 mg/L were derived for algae based on read across information from Hexyl Cinnamic Aldehyde.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 22nd February to 12th March 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The test was conducted according to OECD guidelines and under GLP rules however, it was not possible to test the substance up to its solubility limit fo technical reasons (loss of substance due to its physicochemical properties).
Justification for type of information:
Information used for read across to Acalea.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: final theoretical concentration of test samples was 3.2 mg/L
- Sampling method: Samples were taken from the solvent control and 0.32 mg/L test group at 0 and 72h for quatitative analysis. The samples taken had a volume of 200 mL. An amount of sodium chloride (60g) was added to this volume. The test sample was then extracted with cyclohexane (1x20 mL) to give the final theorethical concentration.
- Sample storage conditions before analysis: The samples taken at 0h were stored at approx -20ºC for further analysis if needed
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus Subspicatus
- Strain: Culture Collection of Algae and Protozoa (CCAP) 276/20
- Source (laboratory, culture collection): Dunstaffnage Marine Laboratory, Oban, Argyll, Scotland.
- Age of inoculum (at test initiation): no data
- Method of cultivation: no data

ACCLIMATION
- Acclimation period: no data
- Culturing media and conditions (same as test or not):
25.5 mg/L of NaNO3
12.164 mg/L of MgCl2.6H2O
4.41 mg/L of CaCl2.2H2O
14.7 mg/L of MgSO4.7H2O
1.044 mg/L of K2HPO4
15.0 mg/L of NaHCO3
0.1855 mg/L of H3BO3
0.415 mg/L of MnCl2.4H2O
0.00327 mg/L of ZnCl2
0.159 mg/L of FeCl3.6H2O
0.00143 mg/L of CoCl2.6H2O
0.00726 mg/L of Na2MoO4.2H2O
0.000012 mg/L of CuCl2.2H2O
0.30 mg/L of Na2EDTA.2H2O
0.000010 mg/L of Na2SeO3.5H2O

the culture medium was prepared using reverse osmosis purified deionised water and the pH was adjusted to 7.5 ±0.1 with 0.1N NaOH or HCl

- Any deformed or abnormal cells observed: no data
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
no data
Test temperature:
the preparations were incubated at 24 ± 1 ºC. The temperature of each incubator was recorded daily
pH:
The pH was measured at initiation of the test and after 72 h exposure It was measured using a WtW pH 320 pHmeter. The pH at the beginning of the test was 7.1 and after 72h it varied from 7.5 to 7.6
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
Nominal concentration was 0.32 mg/L.
Measured concentration at test initiation was found to be 0.361 mg/L (113% of the nominal) in the first replicate and 0.346 mg/L (108% of the nominal in the second replicate.
Measured concentration after 72h of exposure was found to be bellow the Limit of Quantitation (LOQ) in all replicates. The LOQ was determined to be 0.023 mg/L
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.065 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.065 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
- Results with reference substance valid? yes. The results with potassium dichromate were within the normal range
- EC50:
ErC50 (0 -72h): 0.49 mg/L
EyC50 (0 -72h): 0.18 mg/L 95% confidence limits 0.16 -0.21 mg/L
NOEC : 0.0625 mg/L
LOEC : 0.125 mg/L

A decline in measured test concentrations was observed at 72h to less than the limit of quantitation (LOQ) of the analytical method employed which was determined to be 0.023 mg/L. This decline in measured test concentrations was in line with the preliminary stability analyses conducted which indicated that the test item was unstable over the test period, particularly in the light

Current regulatory advice is that in cases where a decline in measured concentrations is observed, geometric mean measured concentrations should be used for calculating EC50 values. However, no EC50 was observed in this case.

based on nominal concentration:

ErC50 (72h) > 0.32 mg/L

EyC50 (72h) > 0.32 mg/L

NOEC (the maximum concentration testable under the conditions of the assay)= 0.32 mg/L

based on geometric mean measured concentrations:

ErC50 (72h) > 0.065 mg/L

EyC50 (72h) > 0.065 mg/L

NOEC (the maximum concentration testable under the conditions of the assay)

= 0.065 mg/L

Validity criteria fulfilled:
yes
Conclusions:
Based on Geometric Mean Measured test concentrations the EC50 values were estimated to be greater than 0.065 mg/L. Correspondingly the No Observed Effect Concentration (NOEC) was 0.065 mg/L (the highest measured concentration attainable under the conditions of the study).
The test was conducted following OECD Guidelines 201 under GLP rules
NOEC based on nominal concentration = 0.32 mg/L (highest concentration testable under the conditions of the study)
Executive summary:

The study was performed to assess the effect of the test item on the growth of the green alga Desmodesmus subspicatus following OECD Guideline 201. Following a preliminary range-finding test, the alga was exposed to an aqueous solution of the test item at a concentration of 0.32 mg/L (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24±1ºC. Exposure of Desmodesmus subspicatus to the test item gave EC50 values of greater than 0.32 mg/L and correspondingly the NOEC was 0.32 mg/l. The test concentration of 0.32 mg/l was the highest attainable test concentration that could be prepared due to the limited solubility of the test item in water and auxiliary solvent, and having due regard to the amount of auxiliary solvent permitted in the test under the OECD Guidelines. Based on the geometric mean measured test concentrations, exposure of the alga to the test item gave EC50 values of greater than 0.065 mg/l and correspondingly the NOEC was considered to be 0.065 mg/l, the maximum attainable concentration under the conditions of the test. However these were a result of unavoidable loss of test substance due to abiotic (and possibly biotic) degradation of the test substance under the conditions of the assay and as no effects were observed cannot be used to derive an EC50 or a NOEC.

Description of key information

For Acalea a 72-h EC50 > 0.065 mg/L and a 72-h NOEC >= 0.065 mg/L were derived for algae based on read across information from Hexyl Cinnamic Aldehyde.

Key value for chemical safety assessment

Additional information

The experimental information from the source is presented here. The read across justification is presented in the overal Aquatic Endpoint Summary.

Hexyl Cinnamic Aldehyde and its toxicity to aquatic algae (copied from the Lead Registrant):

"The study was performed to assess the effect of the test item on the growth of the green alga Desmodesmus subspicatus following OECD Guideline 201. Following a preliminary range-finding test, the alga was exposed to an aqueous solution of the test item at a concentration of 0.32 mg/L (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24±1ºC. Exposure of Desmodesmus subspicatus to the test item gave EC50 values of greater than 0.32 mg/L and correspondingly the NOEC was 0.32 mg/l. The test concentration of 0.32 mg/l was the highest attainable test concentration that could be prepared due to the limited solubility of the test item in water and auxiliary solvent, and having due regard to the amount of auxiliary solvent permitted in the test under the OECD Guidelines. Based on the geometric mean measured test concentrations, exposure of the alga to the test item gave EC50 values of greater than 0.065 mg/l and correspondingly the NOEC was considered to be 0.065 mg/l, the maximum attainable concentration under the conditions of the test. However these were a result of unavoidable loss of test substance due to abiotic (and possibly biotic) degradation of the test substance under the conditions of the assay and as no effects were observed cannot be used to derive an EC50 or a NOEC".