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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
From 2017-02-20 to 2017-02-23
Reliability:
1 (reliable without restriction)
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 v2.3

2. MODEL (incl. version number)
iSafeRat® holistic HA-QSAR v1.7

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CC1CCCCCCCCCCCCC(=O)C1
The water solubility given as input was experimentally measured: 0.43 mg/L

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)
Principles of method if other than guideline:
The acute toxicity to aquatic algae was determined using a validated QSAR for the Mode of Action in question, based on validated data derived from 72-hour ErC50 tests on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period. The QSAR is a simple linear regression of sub-cooled liquid solubility versus 72-h ErC50 for algae and is valid within the applicability domain defined in the QMRF.
GLP compliance:
no
Specific details on test material used for the study:
- Water solubility: 0.43 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: algae spp.
Details on test organisms:
Not applicable
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
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: > subcooled liquid water solubility value
Details on results:
The substance falls within the applicability domain of the model except for the descriptor domain. From a descriptor domain point of view, the substance falls within the intermediate domain where baseline toxicity cannot be experimentally measured accurately.
Moreover the toxicity is likely greater than the water solubility limit. Based on a statistical k-NN approach (k = 3), the predicted toxicity (72h-ErC50) to algae is considered as greater than the subcooled liquid water solubility value within the exposure period of the test.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Not determinable

No additional information

Validity criteria fulfilled:
yes
Remarks:
The substance falls within the applicability domain of the model except for the descriptor domain. However, the substance falls within the intermediate descriptor domain where baseline toxicity cannot be experimentally measured accurately.
Conclusions:
The 72h-ErC50 of the substance in an algal growth inhibition test is greater than the subcooled liquid water solubility value within the exposure period of the test. No acute toxicity is expected at levels up to the water solubility.
Executive summary:

A QSAR prediction 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, (MOA 1, non-polar narcosis). This QSAR 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 substance had been determined by chemical analyses over the test period. The water solubility value of the substance given as the input to the Ecotox module of the iSafeRat® Holistic HAQSAR was experimentally measured at 0.43 mg/L and does not fall within the descriptor domain of the model between a log water solubility (in log (mol/L)) of - 4.38 to 0.49. However it falls within the domain between a log water solubility of - 9.34 to - 4.38 where baseline toxicity cannot be experimentally measured accurately. Moreover the toxicity is likely greater than the water solubility limit. Based on a statistical k-NN approach (k = 3), the toxicity of the test item is considered as greater than the subcooled liquid water solubility value within the exposure period of the test.

No acute toxicity to aquatic algae is expected at levels up to the water solubility.

Description of key information

QSAR model, iSafeRat® holistic HA-QSAR v1.6, key study, validity 1:

72h-ErC50 > water solubility limit

Key value for chemical safety assessment

Additional information

To assess the toxicity of the registered substance to aquatic algae, one data point is available.

This endpoint value (KREATiS, 2017), assessed as a key datapoint, is a QSAR. This QSAR prediction (iSafeRat® holistic HA-QSAR v1.7) was performed to assess the inhibition of growth to algae of the registered 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 1, non-polar narcosis). This QSAR 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 substance had been determined by chemical analyses over the test period . The water solubility value of the substance given as the input was experimentally measured at 0.43 mg/L and does not fall within the descriptor domain of the regression line which has been validated for substances with a water solubility (in mol/L) between a log water solubility (in log units) of - 4.38 to 0.49. However it does fall within a second zone with even lower water solubility which is described as the intermediate domain between a log water solubility of - 9.34 to - 4.38 where baseline toxicity cannot be experimentally measured accurately. Moreover, the solubility is so low for the registered substance that the toxicity is likely greater than the water solubility limit. Based on a statistical k-NN approach (k = 3), the toxicity of the test item is considered as greater than the subcooled liquid water solubility value within the exposure period of the test. No acute toxicity to aquatic algae is expected at levels up to the water solubility.