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Toxicity to microorganisms

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Description of key information

It can be concluded that L-threonine is rapidly oxidized in activated sludge. This leads to the conclusion that it does not show toxic effects to the microorgnism population of activated sludges.

Key value for chemical safety assessment

Additional information

DL-Threonine did not show significant toxic effects to the population of microrganisms in waste water (activated sludge) at a nominal concentration of 500 mg/l. Read-across from DL-threonine to L-threonine was applied because of similar physico-chemical characteristics, a similar toxicological/ecotoxicological profile and the structural similarity of racemic threonine to the enantiomer L-threonine. One can expect that the equivalent concentrations of L-threonine will not show toxic effects in this test system. Instead of DL-threonine, L-threonine is a natural constituent of most living cells, is involved in many metabolic pathways and more subject to undergo biodegradation.

Further, in another not well documented study 18 amino acids were examined for biodagradability and toxic degradation inhibition. In this study L-threonine in aconcentration of approx. 210 mg/l shows no toxic inhibition (0%) according to Offhaus.

The summation of results leads to the conclusion that L-threonine is readily biodegradable and non-toxic to sludge microorganisms.

In accordance with REACH Annex VIII, No. 9.1.4 column 2, the toxicity test to microorganisms does not need to be conducted as there are mitigating factors indicating that the microbial toxicity is unlikely to occur as well as because the substance is readily biodegradable.