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Ecotoxicological information

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)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Study period:
2016-03-07 to 2016-03-08
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Calculation method is used ; calculation method applicable for the endpoint
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
calculation method
Principles of method if other than guideline:
The acute toxicity to daphnia 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 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 EC50s 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 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
Analytical monitoring:
no
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 but extremely low or high temperatures could influence the solubility of certain constituents. Therefore, the calculation method is considered acceptable to determine EL50s for daphnia 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
Key result
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
12 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
not applicable
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
not applicable

Table 6.1.3/1: Short-tetm toxicity to Daphnids values for components used in the calculation.

constituents

48h-EC50 (mg/L)

α-terpineol

61

γ-terpineol

61

β-terpineol

51

terpinolene

0.73

3-terpinen-1-ol

61

borneol

23

fenchol

23

terpinen-1-ol 4

61

limonene

0.62

Table 6.1.3/2: Expected concentrations at this 48h-EL50.

constituents

concentration in the WAF (mg/L)

α-terpineol

7.4

γ-terpineol

1.2

β-terpineol

0.61

terpinolene

1.2

3-terpinen-1-ol

0.42

borneol

0.48

fenchol

0.29

terpinen-1-ol 4

0.19

limonene

0.07

Validity criteria fulfilled:
yes
Conclusions:
The 48h-EL50 for Terpineol multiconstituent is estimated at 12 mg test item/L.
Executive summary:

The registered substance is a multiconstituent substance with a well-defined composition for which the relative percentage and the reported variation of each constituent is known. Its acute toxicity to aquatic invertebrates property 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 worst case composition was 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.

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 EC50s 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 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 48-h EL50 was 12 mg test material/L for the registered substance. EL50 was based on immobility. 

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

Description of key information

The substance exhibits an EL50 for freshwater invertebrates of 12 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
12 mg/L

Additional information

The registered substance is a multiconstituent substance with a well-defined composition for which the relative percentage of each constituent is known. The ecotoxicological properties of the registered substance may be derived from the aquatic toxicity values of the individual components using an additivity calculation approach.

It has been observed that CLP additivity calculations for mode of action 1 compounds are unreasonably conservative when compared to classic experimental studies using Water Accommodated Fractions (WAF), and this has been proved in a number of cases with substances of natural origin. Indeed, substance of natural origin may be composed of hydrophilic alcohol molecules and hydrophobic hydrocarbon 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 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. On the other hand, the CLP additivity approach is calculated on the basis that all the substances are at their maximum solubility. 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 EC50s 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 of the WAF.

A predicted acute toxicity value to Daphnid is available. The estimated EL50 for Daphnid is 12 mg/L. This prediction is obtained with QSAR for the Mode of Action 1, based on validated data derived from standard toxicity test, for which the concentrations of the test item had been determined by chemical analyses over the test period. The prediction is sufficiently robust, and is appropriate for the purposes of chemical safety assessment required for REACH.

Besides, one reliable experimental study is available for the registered substance. The toxicity to Daphnia magna was studied according to OECD TG No. 202 and GLP. Daphnids were exposed to substance at nominal test concentrations of 0 (test medium control), 40, 48, 58, 69, 83 and 100 mg/L over a test period of 48 hours (static test). Concentrations were verified by TOC determinations at relevant concentrations (69 and 100 mg/L). The endpoint was based on the nominal concentrations. The 48-h EC50 was approximately 73 mg/L. Sublethal effects were observed at the concentration equal or higher than 69 mg of terpineol multiconstituent /L: abnormal swimming behaviour.