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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

Pine needle oil (Pine, Abies siberica, ext.) 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. Indeed these variations lead to the identification of two qualities, one named Russia, the other named China. Both qualities were tested to be sure that the worst case composition is clearly taken into account for the endpoint definition. The acute toxicity to aquatic invertebrates property has been investigated using an in-house calculation method that mimics an OECD 202 study and guideline for Testing of Chemicals No. 23 (i.e. WAF conditions) (details are given below. Two theoretical compositions have been investigated for each quality (Russia and China), the “typical” composition proposed by the supplier and a theoretical worst case composition that maximizes the concentration of the most toxic constituents. The 48-h EL50 was 6.4 and 3.6 mg test material/L for the typical composition of Pine needle oil (Pine, Abies siberica, ext.) Russia and China respectively, and the 48-h EL50 was 2.7 mg test material/L for the both theoretical worst case composition. EL50 were based on mortality.Conclusion: The 48-h EL50 for aquatic invertebrates was calculated at 6.4 and 3.6 mg test material/L for the typical composition of Pine needle oil (Pine, Abies siberica, ext.) Russia and China respectively, and the 48-h EL50 was 2.7 mg test material/L for the both theoretical worst case composition.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
2.7 mg/L

Additional information

Pine needle oil (Pine,Abies siberica, ext.) is a Natural Complex Substance (UVCB) with a well-defined composition for which the relative percentage of each constituent is known.Indeed these variations lead to the identification of two qualities, one named Russia, the other named China. Both qualities were tested to be sure that the worst case composition is clearly taken into account for the endpoint definition.

Therefore, it has been decided that the ecotoxicity ofPine needle oil (Pine,Abies siberica, ext.)will be derived from knowledge of the constituents.  The mixture ecotoxicity properties may be derived from the ecotoxicity of the individual constituents using the CLP additivity calculation approach.

 However, it has been observed that CLP additivity calculations for mode of action 1 compounds are unreasonably conservative when compared to classic WAF studies, and 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 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 rate of the WAF.

 

 

Using this approach, the48-h EL50 for aquatic invertebrates was calculated at 6.4 and 3.6 mg test material/L for the typical composition of Pine needle oil (Pine,Abies siberica, ext.) Russia and China respectively, and the 48-h EL50 was 2.7 mg test material/L for the both theoretical worst case composition.These EL50 were based on mortality. 

The in-house calculation has been designed to mimic the behaviour of the mixture in a WAF test where the final toxicity is calculated by additivity of the residual bioavailable fraction of each constituent. This approach has been validated using a Natural Complex Substance similar toPine needle oil (Pine,Abies siberica, ext.) (Details on the validations are available in the attached position paper). This calculation is therefore more accurate than the CLP method accurate but remains conservative compared to the experimental value.

 

Based on the results of this study, Pine needle oil (Pine,Abies siberica, ext.) 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 fulfil the aquatic invertebrate toxicity endpoint.