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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Waiving of experimental study. EC50 for algae was calculated to be ca. 2651 mg/L.

Key value for chemical safety assessment

Additional information

Data from a higher trophic level (fish) are available which show that aquatic toxicity does not occur. Aquatic toxicity also does not occur at the trophic level of invertebrates (Daphnia magna). In accordance with Annex XI No. 1.2 an experimental study is not conducted as there is sufficient weight of evidence from several independent sources of information leading to the assumption/conclusion that the substance does not cause aquatic toxicity to algae.

This is supported by an estimation of EC50 by calculation, by read-across from an experimental study with the structural analogue L-alanine as well as supplementary notes as an expert statement.

EC50 for algae was calculated to be ca. 2651 mg/L. Considering the fact that calculation models for aquatic toxicity to algae usually produce values which are conservative to unrealistic conservative, even the estimated high EC50 does not reflect actual aquatic toxicity to algae by L-valine. Higher EC50 is expected.

Read-across from the structural analogue L-alanine is deemed justified based on a comparison of the main factors driving environmental toxicity: pH, water solubility, log Kow, functional groups and functional groups:

- both are essential amino acids that are in the zwitterion state at physiological pH

- the chemical structure differs only in that L-alanine has a shorter alkyl chain

- the pKa values of the α-COOH group is similar

- the pKa values of the α-NH2 group is similar

- the substances both have a high water solubility

- the substances both have a low log Kow value.

As the chemical structure and the functional groups, as well as the water solubility, log Kow and pKa values of L-alanine and L-leucine are almost identical, it can be concluded that read-across for aquatic toxicity information between those 2 substances is acceptable.

L-leucine is a naturally occurring essential amino acid which is omnipresent in nature. It is a basic metabolite and building block of all living organisms and cells and is also a nutrient for algae. Thus significant toxicity to algae can be excluded.