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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)
Adequacy of study:
key study
Study period:
2014-07-21 to 2014-07-23
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Calculation method is used ; calculation method applicable for the endpoint.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
calculation method
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. 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. Each value and calculation 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 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:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
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: 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 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 but extremely low or high temperatures could influence the solubility of certain constituents. Therefore, the calculation method is considered acceptable to determine EL50s for algae between 12 and 28°C.
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. However as the fish QSAR for the constituents calculation was based on data from freshwater studies, the resulting calculation is considered valid for freshwater organisms
Nominal and measured concentrations:
The calculation determines measured concentrations
Details on test conditions:
calculation method
Reference substance (positive control):
not required
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
5.6 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
4.4 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
not applicable
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
not applicable

Table 1: Expected concentrations at this 72h-ErL50 (composition 1: typical composition)

constituents

concentration in the WAF (mg.L-1)

cineol-1,8

0.58

limonene

0.21

α-pinene

1.32

camphor

0.97

terpineol

0.15

β-pinene

0.15

p-cymene

0.10

camphene

0.42

Table 2: Expected concentrations at this 72h-ErL50 (composition 2 : theoretical worst case composition)

constituents

concentration in the WAF (mg.L-1)

cineol-1,8

1.06

limonene

0.31

α-pinene

1.10

camphor

0.84

terpineol

0.24

β-pinene

0.18

p-cymene

0.15

camphene

0.39

Validity criteria fulfilled:
yes
Conclusions:
72h-ErL50 for typical composition of Rosemary oil = 5.6 mg test item/L and 72h-ErL50 for theoritecal worst composition of Rosemary oil = 4.4 mg test item/L.
Executive summary:

Rosemary oil is a Natural Complex Substance (UVCB) with a well-defined composition for which the relative percentage and its reported variation of each constituent is known. Its acute toxicity to aquatic algae property 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). Two theoretical compositions have been investigated, the “typical” composition proposed by the Lead registrant and a theoretical worst case composition that maximizes the concentration of the most toxic constituents. The acute toxicity to algae was determined using a calculation method for Mode of Action 1 (non-polar narcotics) for each individual constituent present in the mixture.

 

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 ErC50s 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 72-h ErL50 was 5.6 mg test material/L for the typical composition of Rosemary oil, and The 72-h ErL50 was 4.4 mg test material/L for the theoretical worst case composition. ErL50 were based on growth rate.

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

 

Results Synopsis

Test Type: Calculation method

ErL50: 5.6 mg test material/L for typical composition

ErL50: 4.4 mg test material/L for theoretical worst case composition

Description of key information

Rosemary oil is a Natural Complex Substance (UVCB) with a well-defined composition for which the relative percentage and its reported variation of each constituent is known. The acute toxicity to aquatic algae property has been investigated using an in-house calculation method that mimics an OECD 201 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions). The acute toxicity to aquatic algae was determined using a calculation method for Mode of Action 1 (non-polar narcotics) for each individual constituent present in the mixture. This algorithm is based on a QSAR model which has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004). Further to this the lethal loading rate of the WAF is determined by using a series of calculation steps using phase equilibrium thermodynamics first to determine the analyzable fraction (the concentration which should be analyzable in a WAF study) and then excluding the non-bioavailable fraction of the remaining constituents. The remaining bioavailable fraction corresponds to the lethal loading value of the mixture. This approach has been validated using data derived from 48-hour ErL50 tests on algae (OECD 201 study and the OECD guidance document on toxicity testing for difficult substances and mixtures No. 23, i.e. WAF conditions). Two theoretical compositions have been investigated, the “typical” composition proposed by the Lead registrant and a theoretical worst case composition that maximizes the concentration of the most toxic constituents. The 72-h ErL50 was 5.6 mg test material/L for the typical composition of Rosemary oil, and the 72-h ErL50 was 4.4 mg test material/L for the theoretical worst case composition. ErL50 were based on growth rate.  

Key value for chemical safety assessment

EC50 for freshwater algae:
4.4 mg/L

Additional information

Rosemary oil is a Natural Complex Substance (UVCB) with a well-defined composition for which the relative percentage of each constituent is known. Therefore, it has been decided that the ecotoxicity of Rosemary oil will be derived from knowledge of the constituents; constituents approach. The mixture ecotoxicity properties may be derived from the ecotoxicity of the individual constituents (table 1) using the CLP additivity calculation approach.

However, CLP additivity approach is calculated on the basis that all the substances are at their maximum solubility and it has been observed that CLP additivity calculations for mode of action 1 compounds are unreasonably conservative when compared to classic WAF studies. This has been proved in a number of cases for natural complex substances. Indeed, natural extract compositions are a mixture of hydrophilic alcohol molecules and hydrophobic terpene molecules. Therefore, when a WAF is performed most of substances fully dissolved in the aqueous phase are the hydrophilic fraction while the hydrophobic fraction (the more toxic elements for MOA 1 substances) may be below their water solubility value.

The acute toxicity to algae property for Rosemary oil has been investigated using a calculation method (iSafeRat® WAF module for mixture toxicity calculation) that mimics an OECD 201 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions). Two theoretical compositions have been investigated, the “typical” composition proposed by the Lead registrant and a theoretical worst case composition that maximizes the concentration of the most toxic constituents. The acute toxicity to algae was determined using a calculation method for Mode of Action 1 (non-polar narcotics) for each individual constituent present in the mixture.

 

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 ErC50s of each constituent are already known from literature or predicted using the iSafeRat® QSAR model (table 1). 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.

 

Table1 Rosemary oil, constituents data used to derive Rosemary oil Ecotoxicity value.

 

constituent

typical composition

(%)

worst case concentration (%)

72h-algae ErC50

(mg/L)

72h-algae ErC50

reference

α-pinene

23.57

25.00

> 0.494

literature source

cineol 1,8

17.54

24.00

> 74

literature source

limonene

3.83

7.00

1.13

[0.72 – 1.76]

literature source

terpineol

2.70

5.40

66.85

[48.61 – 91.92]

iSafeRat® prediction

para-cymene

1.87

3.50

1.70

[1.13 – 2.55]

iSafeRat® prediction

β-pinene

2.63

4.00

0.45

[0.26 – 0.78]

iSafeRat® prediction

Camphene

9.70

11.00

0.45

[0.26 – 0.78]

iSafeRat® prediction

camphor

17.29

19.00

23.80

[18.05 – 31.40]

iSafeRat® prediction

 

Using this approach, the 72-h ErL50 for aquatic algae was 5.6 mg test material/L for the typical composition of Rosemary oil, and the 72-h ErL50 was 4.4 mg test material/L for the theoretical worst case composition. These ErL50 were based on growth rate.

Validation document of iSafeRat® is attached to the dossier.

 

Based on the results of this study, Rosemary oil would not be classified as acutely toxic to aquatic organisms in accordance with the classification of the CLP.

This toxicity prediction has been validated and is considered acceptable to fulfill the aquatic algae toxicity endpoint.