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Biodegradation in water: screening tests

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Description of key information

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

L-Threonine was predicted to be readily biodegradable by using the calculation method BIOWIN (Version 4.10). The suitability of the model was assessed and it was concluded that L-threonine is considered to be inside the applicability domain of the EpiSuite BIOWIN model.

The study using the calculation method was considered the most reliable one in comparison to the other applicable studies. Thus, it was chosen as the key study.

A supporting study with DL-threonine also indicates that L-threonine is readily biodegradable. DL-Threonine is rapidly oxidized by activated sludge. After only 24 h already 16.2% of the Theoretical Oxygen Demand were achieved. 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 also be rapidly oxidised in activated sludge. 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.

Three other supporting studies were considered to be less reliable, because their documentation was limited. The experimental results of these three supporting studies also consistently indicate that L-threonine is readily biodegradable.