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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

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Administrative data

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Description of key information

Only very old test results for L-isoleucine are available. Hence, read-across to L-valine was selected as the key information.

Based on test results available for read-across substance L-valine it can be concluded that toxicity to microorganisms is not expected to occur upon exposure to >= 1120 mg/kg of L-isoleucine.

The old experiment by Dawson and Jenkins is added as supporting information to this dossier.

In the experiment, the uptake of oxygen from a Warburg manometer containing activated sludge and the test substance was monitored.

Addition of a 5% solution of the test substance to the Warburg manometer resulted in an increase of the oxygen uptake of 36%.

As a consequence, this test shows that the test substance is not toxic to the micro-organisms present in the activated sludge.

Key value for chemical safety assessment

Additional information

Only limited test results for L-isoleucine are available. Read-across to the test results available for structural analogue L-valine is deemed justified based on a comparison of the main factors driving environmental toxicity: pH, water solubility, log Kow and chemical reactivity (functional groups).

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

- the chemical structure differs only in that L-isoleucine has one extra methylene group in the aliphatic side chain

- the pKa values of the α-COOH group is very similar: 2.36 for ILE, 2.32 for VAL

- the pKa values of the α-NH2 group is very similar: 9.60 for ILE, 9.62 for VAL

- the substances both have a high water solubility: 34 - 41 g/L for ILE, 58 g/L for VAL

- the substances both have a low log Kow value: -1.72 for ILE (experimental value obtained from EpiSuite's WSKOW model database), -2.08 for VAL (calculated by EpiWin QSAR)

As the chemical structure and reactivity, and the water solubility, low Kow and pKa values of L-isoleucine and L-valine are almost identical, it can be concluded that read-across for aquatic toxicity information between those 2 substances is acceptable.

The test available for L-valine is carried out according to OECD guidelines and reveals no growth inhibition at the highest tested concentrations (9900 mg/kg) after 16 hours. As a consequence, toxicity to microorganisms is not expected to occur upon exposure to L-valine at a concentration >= 1000 mg/kg.

Recalculation of this value taking into account the molecular weight of L-isoleucine allows to concluded that no toxicity is expected to occur at a concentration of 1120 mg/L for L-isoleucine.