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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
July 18th, 2016 to July 19th, 2016
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
yes
Remarks:
Calculation method
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
yes
Remarks:
Calculation method
Principles of method if other than guideline:
The growth inhibition of algae was determined using validated QSAR model for the Mode of Action in question, i.e. non-polar narcosis (MOA1). The QSAR model is based on validated data for a training set of 40 chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period.
GLP compliance:
no
Analytical monitoring:
no
Details on sampling:
Not applicable
Vehicle:
no
Details on test solutions:
Not applicable
Test organisms (species):
other: Results from the following species were used in the regression: Pseudokirchneriella subcapitata, Desmodesmus subspicatus, Scenedesmus quadricauda
Details on test organisms:
Following the principles of Phase Equilibrium Thermodynamics, for narcotic substances, no difference in relationship between solubility and ecotoxicity between algae (or indeed other) aquatic species is expected. Any observed differences may be attributed to lifestyle related parameters and relative duration of study versus bodysize rather than to a specific toxic mechanism causing species differences. In this case, for esters, no differences were observed in activity based toxicity for the 3 species used.
Test type:
other: QSAR
Water media type:
not specified
Total exposure duration:
72 h
Remarks on exposure duration:
72h-ErC50
Post exposure observation period:
Not applicable
Hardness:
No data
Test temperature:
The temperatures varied from approximately 20 to 25 °C depending on the species used to construct the algorithm. This small difference is not expected to contribute to the variability of the ErC50 values found in experimental data.
pH:
Test results were preferably taken from studies with measured pHs between 6 - 9. However it is recognized that in some cases (due to high luminosity) the pH may increase in the control and lower concentrations (which do not cause significant effect over the study period). This pH increase did not generally disqualify the study from being used in the test and validation set for non-polar chemicals.
Dissolved oxygen:
No data
Salinity:
No data
Conductivity:
No data
Nominal and measured concentrations:
No data
Details on test conditions:
Results from a test duration of 72 hours only were used for this algorithm. Following OECD 201, all studies were from a static test design. For suspected volatile substances only tests performed in closed vessels were accepted unless accompanying analytical monitoring proved such a design was not necessary.
Reference substance (positive control):
not required
Key result
Duration:
72 h
Dose descriptor:
other: ErC50
Effect conc.:
0.97 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
95% CL: 0.91 - 1.0 mg/L
Details on results:
- The result above is the toxicity value anticipated further to 72-hour study on growth algae based on measured concentrations.
- Adequacy of prediction: The log water solubility value given as input to the iSafeRat® Ecotox module (-4.64) is just outside of the applicability domain defined for the model (-4.38 to 0.49). However, it falls within an intermediate zone where the ecotoxicity value of a substance is expected to be between the hypothetical value as predicted by iSafeRat® model and the water solubility value. Therefore, the toxicity value (72h-EC50) to algae for the test item was determined as the geometric mean of the iSafeRat® prediction and the subcooled water solubility limit (see QPRF). Moreover the test substance is attributed to the class of non-polar narcotic compounds (MOA 1).
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Not applicable

None

Validity criteria fulfilled:
yes
Conclusions:
The 72 h-ErC50 for (E,Z)-2,6-dimethylocta-2,4,6-triene is 0.97 mg/L.
Executive summary:

A QSAR model was used to calculate the inhibition of growth to algae of test item (E,Z)-2,6-dimethylocta-2,4,6-triene. This QSAR model has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following Guideline for Testing of Chemicals No. 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test", referenced as Method C.3 of Commission Regulation No. 440/2008. The criterion predicted was the ErC50 (Median Effective Concentration for specific growth rate), a statistically derived concentration which is expected to cause 50% inhibition of intrinsic rate of growth of the test system within a period of 72 hours.

The growth inhibition of algae was determined using validated QSAR model for the Mode of Action in question, i.e. non-polar narcosis (MOA1). The QSAR model is based on validated data for a training set of 40 chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period.

The result hereafter is the toxicity values anticipated further to a 72-hour study on algae based on measured concentrations: the predicted 72-hour ErC50 is 0.97 mg/L.

Based on the results of this study, the substance is classified in category 1 for acute toxicity and for long-term toxicity according to CLP regulation (EC) No 1272/2008 and GHS regulation. Hazard sentences H400 and H410 are required as well as signal word Danger.

Description of key information

The 72 h-ErC50 for (E,Z)-2,6-dimethylocta-2,4,6-triene is 0.97 mg/L.

The criterion predicted was the ErC50 (Median Effective Concentration for specific growth rate), a statistically derived concentration which is expected to cause 50% inhibition of intrinsic rate of growth of the test system within a period of 72 hours.

Based on the result of this study, the substance is classified in category 1 for acute toxicity and for long-term toxicity according to CLP regulation (EC) No 1272/2008 and GHS regulation. Hazard sentences H400 and H410 are required as well as signal word Danger.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.97 mg/L

Additional information

A QSAR model was used to calculate the inhibition of growth to algae of test item (E,Z)-2,6-dimethylocta-2,4,6-triene. This QSAR model has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following Guideline OECD 201.

The growth inhibition of algae was determined using validated QSAR model for the Mode of Action in question, i.e. non-polar narcosis (MOA1). The QSAR model is based on validated data for a training set of 40 chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period.