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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Study period:
From 2018-08-24 to 2018-08-24
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:
See QMRF and QPRF in "attached background material" section.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
QSAR model
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
yes
Remarks:
QSAR model
Principles of method if other than guideline:
The acute toxicity to the daphnids was determined using a calculation method for the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis). The QSAR model is based on validated data for a training set of 58 chemicals derived from 48-hour test on daphnids, for which the concentrations of the test item had been determined by chemical analyses over the test period.
The first step of the iSafeRat mixture toxicity calculation employs phase equilibrium thermodynamics in order to determine the concentrations of each constituent within the WAF. This fraction equates to the analyzable fraction of a WAF study.
Within the WAF, the constituents also partition between themselves further reducing the bioavailable fraction and thus the toxicity of the mixture compared to the individual constituents.
The method has been validated using data derived from 48-hour EC50 tests on aquatic invertebrates, for which the concentrations of the test item had been determined by chemical analyses over the test period. Further to this the effective loading rate of the WAF is determined by using a series of calculation steps using phase equilibrium thermodynamics and excluding the non-bioavailable fraction.
GLP compliance:
no
Specific details on test material used for the study:
None.
Analytical monitoring:
not required
Details on sampling:
Not applicable.
Vehicle:
no
Details on test solutions:
Not applicable.
Test organisms (species):
Daphnia sp.
Details on test organisms:
Not applicable.
Test type:
other: Calculation method
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Remarks on exposure duration:
48h-EL50 (effective loading rate of WAF)
Post exposure observation period:
Not applicable.
Hardness:
Hardness is not a necessary component of the WAF calculation
Test temperature:
The Temperature is not a necessary component of the WAF calculation.
pH:
The pH is not a necessary component of the WAF calculation
Dissolved oxygen:
The oxygen concentration is not a necessary component of the WAF calculation
Salinity:
Salinity is not a necessary component of the WAF calculation.
Nominal and measured concentrations:
The calculation determines measured concentrations.
Details on test conditions:
Calculation method.
Reference substance (positive control):
not specified
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
6.3 mg/L
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: Results based on typical composition
Details on results:
Not applicable.
Results with reference substance (positive control):
Not applicable.
Reported statistics and error estimates:
Not applicable.

At this 48-hour EL50 the expected concentrations of each constituent in the mixture (based on thermodynamic calculation) are as follows:

constituents concentration in the WAF (mg.L-1)
Constituent 1 0.93
Constituent 2 0.8
Constituent 3 0.72
Constituent 4 0.7
Constituent 5 0.38
Constituent 6 0.3
Constituent 7 0.22
Constituent 8 0.27
Constituent 9 0.18
Constituent 10 0.19
Constituent 11 0.15
Constituent 12 0.15
Constituent 13 0.11
Constituent 14 0.1
Constituent 15 0.1
Constituent 16 0.094
Constituent 17 0.088
Constituent 18 0.082
Constituent 19 0.069
Validity criteria fulfilled:
yes
Conclusions:
Calculated 48h-EL50 of Thuja Oil to Daphnia magna for the typical composition provided by the sponsor is of 6.3 mg/L.
Executive summary:

Thuja Oil is a Natural Complex Substance (UVCB) with a well-defined composition (92.1%). Its acute toxicity to aquatic invertebrates has been investigated using an in-house calculation method that replaces an OECD 202 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions). The typical composition of the substance provided by the supplier of the has been investigated.

The first step of the iSafeRat mixture toxicity calculation employs phase equilibrium thermodynamics in order to determine the concentrations of each constituent within the WAF. This fraction equates to the analysable fraction of a WAF study. In the calculation the second step is to remove this non-bioavailable fraction. Within the WAF, the constituents also partition between themselves further reducing the bioavailable fraction and thus the toxicity of the mixture compared to the individual constituents.

These two reasons explain why ecotoxicity values from WAF studies are always higher for non-polar narcotic mixtures than the calculated values from CLP additivity calculation.The final step is to determine the truly bioavailable fraction of the WAF per constituent. The EC50s of each constituent are already known from literature or predicted using the iSafeRat QSAR model. Each value has been included as a supporting study in the IUCLID. An additivity approach (based on Chemical Activity of each constituent) is used in order to calculate the Effective Loading rate of the WAF.

The 48h-EL50 was 6.3 mg test item/L for the typical composition of Thuja Oil.

This toxicity study is acceptable and can be used for that endpoint.

 

Results Synopsis

Test Type: Calculation method

48h-EL50: 6.3 mg test material/L based on the typical composition

Description of key information

A calculation methodthat replaces an OECD 202 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions) has been used to assess the acute toxicity of Thuja Oil to aquatic invertebrate.

A 48h-EL50 of 6.3 mg/Lhas been estimated.

Based on the results of this study, Thuja oil would not be classified as acute 1 to aquatic organisms in accordance with the classification of the CLP.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
6.3 mg/L

Additional information

Thuja Oil is a Natural Complex Substance (UVCB) with a well-defined composition (92.1%). Its acute toxicity to aquatic invertebrates has been investigated using an in-house calculation method that replaces an OECD 202 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions). The typical composition of the substance provided by the supplier of the has been investigated.

The first step of the iSafeRat mixture toxicity calculation employs phase equilibrium thermodynamics in order to determine the concentrations of each constituent within the WAF. This fraction equates to the analysable fraction of a WAF study. In the calculation the second step is to remove this non-bioavailable fraction. Within the WAF, the constituents also partition between themselves further reducing the bioavailable fraction and thus the toxicity of the mixture compared to the individual constituents.

These two reasons explain why ecotoxicity values from WAF studies are always higher for non-polar narcotic mixtures than the calculated values from CLP additivity calculation.The final step is to determine the truly bioavailable fraction of the WAF per constituent. The EC50s of each constituent are already known from literature or predicted using the iSafeRat QSAR model. Each value has been included as a supporting study in the IUCLID. An additivity approach (based on Chemical Activity of each constituent) is used in order to calculate the Effective Loading rate of the WAF.

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