Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

A study dating back to 1981 is available in which the biodegradability of leucine was tested according to the Offhaus method. Nevertheless, as this test was not performed according to GLP nor internationally accepted guidelines, read-across to L-valine was considered to be the key approach to address this endpoint.

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-leucine has one extra methylene group in the aliphatic side chain

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

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

- the substances both have a high water solubility: 23 g/L for LEU, 58 g/L for VAL

- the substances both have a low log Kow value: -1.59 for LEU (calculated by EpiWin QSAR), -2.08 for VAL (calculated by EpiWin QSAR)

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

The tests available for L-valine are carried out according to OECD guidelines and reveal that the substance is readily biodegradable within 28 days. As a consequence, it can be concluded that L-leucine will also be readily biodegradable.

This is further confirmed by the result of the supporting study. In this study according to the Offhaus method, it was concluded that degradation should take place undisturbed, even at relatively high concentrations.