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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 2017-01-27 to 2017-01-30
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

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

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O=C1CCC=CCCCCCCCCCC1
The water solubility given as input was experimentally measured: 2.91 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: 2.91 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
Effect conc.:
0.98 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.92-1.0 mg/L
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 the geometric mean of the iSafeRat® prediction and the subcooled water solubility limit.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Not determinable

No additional information

Validity criteria fulfilled:
yes
Conclusions:
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 was determined at 0.98 mg/L (95% CL: 0.92-1.0 mg/L), corresponding to the geometric mean of the iSafeRat® prediction and the subcooled water solubility limit.
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 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 was determined at 0.98 mg/L (95% CL: 0.92-1.0 mg/L), corresponding to the geometric mean of the iSafeRat® prediction and the subcooled water solubility limit.

Description of key information

QSAR model, iSafeRat holistic approach v1.7, key study, reliability 1:

72h-ErC50 (algae) = 0.98 mg/L (95% CL: 0.92 -1.0mg/L).

Key value for chemical safety assessment

EC50 for freshwater algae:
0.98 mg/L

Additional information

To assess the acute toxicity of the registered substance to aquatic algae, one QSAR prediction is available.

This QSAR prediction (KREATiS, 2017; model: 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 substance falls within the applicability domain of the model except for the descriptor domain meaning that the substance falls within the intermediate domain where baseline toxicity can no longer be measured accurately experimentally. According to the test methodology used, the toxicity may even be greater than the water solubility limit. Based on a statistical k-NN approach (k = 3), the predicted toxicity (72h-ErC50) to algae was determined at 0.98 mg/L (95% CL: 0.92-1.0 mg/L), corresponding to the geometric mean of the iSafeRat® prediction for the non-polar narcotic regression line (i.e. the value expected if equilibrium was reached between the test solution and the test organism) and the subcooled water solubility limit of the test substance.

In conclusion, as the same QSAR model was validated for the "short-term toxicity to aquatic invertebrates" endpoint with an experimental study and the results from this prediction was observed to be similar to those obtained from the experimental study, considering the biological and experimental variabilities, this result can be used with high reliability. Therefore, the 72h-ErC50 value on algae was considered to be 0.98 mg/L (95% CL: 0.92 -1.0 mg/L).