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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:
calculation (if not (Q)SAR)
Remarks:
Estimated by calculation
Adequacy of study:
key study
Study period:
2018-02-22 to 2018-04-24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
accepted calculation method
Remarks:
Calculation method is used; calculation method applicable for that endpoint.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
yes
Remarks:
calculation mrthod
Principles of method if other than guideline:
The acute toxicity to aquatic algae was determined using a validated QSAR model for the Mode of Action in question. 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.
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. In the calculation the second step is to remove this non-bioavailable fraction.
The final step is to determine the truly bioavailable fraction of the WAF per constituent. The ErC50s of each constituent are already known from literature or calculated using the iSafeRat QSAR model. An additivity approach (based on Chemical Activity of each constituent) is used in order to calculate the Effective Loading rate of the WAF.
The method has been validated using data derived from 72-hour ErC50 tests on aquatic algae, 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:
not specified
Specific details on test material used for the study:
Not applicable
Analytical monitoring:
not required
Details on sampling:
Not applicable.
Vehicle:
no
Details on test solutions:
Not appliable.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Not appliable
Test type:
other: calculation method
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
72h-ErL50 (effective loading rate of WAF)
Post exposure observation period:
Not appliable.
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 required
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
12 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Based on a typical composition
Details on results:
Not applicable.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Not applicable

Analytically Measured Aqueous Phase (AMAP) calculated at the predicted EL50:

constituents

concentration in the WAF (mg.L-1)

constituent 1

8.0

constituent 2

0.014

constituent 3

0.010

consituent 4

0.0055

constituent 5

0.0035

contituent 6

0.0019

Validity criteria fulfilled:
yes
Conclusions:
The 72h-ErL50 for typical composition of Patchouli EO Fraction Patchoulol Rich is of 12 mg/L.
Executive summary:

Patchouli EO Fraction Patchoulol Rich is a Natural Complex Substance (UVCB) with a well-defined composition. Its acute toxicity to aquatic algae has been investigated using an in-house calculation method that replaces an OECD 201 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions). A typical composition 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 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. In the calculation the second step is to remove this non-bioavailable fraction.

The final step is to determine the truly bioavailable fraction of the WAF per constituent. The ErC50s of each constituent are already known from literature or predicted using the iSafeRat QSAR model. Then, an additivity approach (based on Chemical Activity of each constituent) is used in order to calculate the Effective Loading rate of the WAF.

Using this approach, the 72-h ErL50 was 12 mg test material/L for the typical composition of Patchouli EO Fraction Patchoulol Rich.

 

Results Synopsis

Test Type: Calculation method

ErL50: 12 mg test material/L for typical composition

Description of key information

Based on a calculation method, the following toxicity value has been found for the registered substance:

- 72h-ErL50 = 12 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
12 mg/L

Additional information

For that endpoint, one study with the registered substance was available. Indeed, the toxicity to aquatic algae of the registered substance has been investigated using an in-house calculation method that replaces an OECD 201 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions).

A typical composition of the substance has been investigated. The algorithm used for the purpose of this study is based on a QSAR model which has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004).

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. In the calculation the second step is to remove this non-bioavailable fraction. 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 ErC50s of each constituent were already known from litterature or were predicted using the iSafeRat QSAR model.

Then, an additivity approach (based on Chemical Activity of each constituent) is used in order to calculate the Effective Loading rate of the WAF.

The result below are the toxicity values anticipated during a 72-hour ErL50 study on algae based on the WAF method. The 72-hour ErL50 is calculated as follows:

Composition

Time (h)

ErL50(mg test item.L-1)

typical

72

12

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

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