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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
From 2015-08-04 to 2015-08-05
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
Justification for type of information:
1. SOFTWARE
iSafeRat® HA-QSAR toolbox v2.1

2. MODEL (incl. version number)
iSafeRat® High Accuracy QSAR – version 1.5

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O(c(c(O)ccc1C=CC)c1)C

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached QMRF

5. APPLICABILITY DOMAIN
See attached QPRF

6. ADEQUACY OF THE RESULT
See attached QPRF
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
not applicable
Remarks:
(QSAR model)
Qualifier:
equivalent or similar to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
not applicable
Remarks:
(QSAR model)
Principles of method if other than guideline:
The purpose of these QSAR models is to accurately predict the toxicity to algae as would be expected in a laboratory experiment following OECD Guideline 201 and EC method C.3 for specific, named modes of action to provide a value that can effectively replace a 72-hour NOECr and a 72-hour ErC50 value from an
experimental study. The regressions based method used to achieve this has been fully validated following the OECD (2004) recommendations (refer to the QMRF with KREATiS QMRF identifier: KTS/QMRF/HOL/05 for further details).
GLP compliance:
no
Specific details on test material used for the study:
- Mode of action: MOA2, polar narcotic (alkyl/alkoxyphenols)
- Water solubility: 709 mg/L (from experimental study)
Analytical monitoring:
no
Details on sampling:
Not applicable
Vehicle:
no
Details on test solutions:
Not applicable
Test organisms (species):
other: Pseudokirchneriella subcapitata, Desmodesmus subspicatus, Scenedesmus quadricauda
Details on test organisms:
Results from the following species were used in the regression: Pseudokirchneriella subcapitata, Desmodesmus subspicatus, Scenedesmus quadricauda.
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 MOA 2, no differences were observed in activity based toxicity for the 3 species used..
Test type:
other: QSAR method
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
none
Post exposure observation period:
Not applicable
Hardness:
The QSAR is based on data from studies performed at acceptable hardness to ensure control survival.
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:
The QSAR is based on data from studies performed at acceptable pH between 6.0 - 9.0.
Dissolved oxygen:
The QSAR is based on data from studies performed at acceptable oxygen concentrations (generally >60%).
Salinity:
Not applicable.
Nominal and measured concentrations:
The QSAR is based on data from studies performed using measured concentrations or with acceptable stability.
Details on test conditions:
Not applicable
Reference substance (positive control):
no
Remarks:
QSAR model
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
5.6 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 3.8-8.4 mg/L
Details on results:
The water solubility value given as input to the Ecotox modules of the iSafeRat® HA-QSAR models falls within the descriptor domain of the model between log water solubility (in log (mol/L)) of -5.06 to 0.109. Moreover the test substance is attributed to the class of polar narcotic compounds (MOA 2) as alkyl/alkoxy-phenols.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
95% CL: 3.8-8.4 mg/L.
QSAR statistical parameters are given in the QMRF and the QPRF

No additional information

Validity criteria fulfilled:
yes
Remarks:
The substance falls into applicability domains of the QSAR model
Conclusions:
The 72-h ErC50 based on measured concentrations was determined to be 5.6 mg/L with 95%-Confidence Limit between 3.8 and 8.4 mg/L.
Executive summary:

A QSAR prediction (KREATiS, 2015) was performed to assess the inhibition of growth to algae of the test substance. This QSAR has been validated to be compliant with the OECD recommendations for QSAR modelling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 201. 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 a validated QSAR for the Mode of Action in question (MOA2, polar narcosis). This QSAR is based on validated data for a training set of 8 chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test substance had been determined by chemical analyses over the test period. The water solubility of the substance given as input was experimentally measured at 709 mg/L.The substance falls within the applicability domain of the model as demonstrated in the QPRF.

The 72-h ErC50 based on measured concentrations was determined to be 5.6 mg/L with 95%-Confidence Limit between 3.8 and 8.4 mg/L.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
Run on 2015-09
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 limited documentation / justification
Justification for type of information:
1. SOFTWARE
ECOSAR

2. MODEL (incl. version number)
ECOSAR v1.11

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
Oc(ccc1C=CC)c(c1)OC
log Kow: 2.1 (experimental result)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: Toxicity to aquatic algae.
- Unambiguous algorithm: Linear regression QSAR. Log 96h-EC50 (mmol/L) = -0.6089*log Kow + 0.599. To convert the EC50 from mmol/L to mg/L, multiply by the molecular weight.
- Defined domain of applicability: Applicable to chemicals with log Kow less than 6.4 and molecular weight less than 1000 g/mol. The model can be suitable for chemicals class of Phenols.
- Appropriate measures of goodness-of-fit and robustness and predictivity: N = 40+3 and the coefficient of determination R² = 0.6748.
- Mechanistic interpretation: related to the partitioning of the substance from water into the organisms lipid phase.

5. APPLICABILITY DOMAIN
Applicable to chemicals with log Kow less than 6.4 and molecular weight less than 1000 g/mol. The model can be suitable for chemicals class of Phenols.

6. ADEQUACY OF THE RESULT
The substance falls within the applicability domain described above and therefore the predicted value can be considered reliable. For more information, see Phenols SAR document in "Attached background material".
Qualifier:
according to
Guideline:
other: REACH guidance on QSARs R.6, May 2008
Deviations:
no
Principles of method if other than guideline:
See attached QPRF.
GLP compliance:
no
Remarks:
(not relevant)
Specific details on test material used for the study:
- log Kow : 2.1 (experimental result)
Details on sampling:
Not applicable
Details on test solutions:
Not applicable
Test organisms (species):
other: Green algae
Details on test organisms:
None
Test type:
not specified
Water media type:
not specified
Total exposure duration:
96 h
Remarks on exposure duration:
none
Post exposure observation period:
Not applicable
Hardness:
Not applicable
Test temperature:
Not applicable
pH:
Not applicable
Dissolved oxygen:
Not applicable
Salinity:
Not applicable
Nominal and measured concentrations:
Not applicable
Details on test conditions:
Not applicable
Key result
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
34.3 mg/L
Remarks on result:
other: ECOSAR Class: Phenols
Details on results:
See QPRF report
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
N = 40+3 and the coefficient of determination R² = 0.6748.

None

Validity criteria fulfilled:
yes
Conclusions:
The substance was predicted to have an EC50 value at 34.3 mg/L to green algae after 96h of exposure. The substance falls within the applicability domain and therefore the predicted value can be considered reliable.
Executive summary:

Toxicity to green algae was estimated using the ECOSAR v1.11 QSAR model available from the U.S. EPA. The estimation 96h-EC50 was 34.3 mg/L (Phenols class), calculated from a measured log Kow value at 2.1 and a linear regression:

Log 96h-EC50 (mmol/L) = -0.6089*log Kow + 0.599.

The substance falls within the applicability domain and therefore the predicted value can be considered reliable.

Description of key information

Geometric mean of QSARs models (iSafeRat v1.5 and ECOSAR v1.11):
72/96h-EC50 = 13.9 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
13.9 mg/L

Additional information

To assess the toxicity of the registered substance to aquatic algae, two reliable QSAR results are available.

The first prediction data (KREATiS, 2016) is a QSAR. This QSAR prediction (iSafeRat holistic approach v1.5) was performed on the registered substance, to assess the inhibition of growth to algae of the substance. This QSAR has been validated to be compliant with the OECD recommendations for QSAR modelling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 201. The growth inhibition of algae was determined using a validated QSAR for the Mode of Action in question, (MOA 2, polar narcosis). This QSAR is based on validated data for a training set of 8 chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test substance had been determined by chemical analyses over the test period. The substance falls within the applicability domain of the model. The 72h ErC50 value based on growth rate and measured concentrations was determined to be 5.6 mg/L (95% CL: 3.8 - 8.4 mg/L).

The second prediction data (ECOSAR, 2015) is also a QSAR. This QSAR prediction used the ECOSAR v1.11 QSAR model available from the U.S. EPA to assess the toxicity of the registered substance to green algae. The substance falls within the applicability domain of the model. The estimation 96h-EC50 value was determined at 34.3 mg/L using the chemical class of Phenols.

In conclusion, according to these key data points, the key EC50 value on algae, used for chemical safety assessment, is determined at 13.9 mg/L, corresponding to a geometric mean of predicted EC50 values.