Schiff bases, benzylidene, C16-18 (even numbered) and C18-unsaturated alkyl

Toxicity to aquatic algae and cyanobacteria

Description of key information

The target substance (TS) is a multiconstituent substance, containing seven constituents. The acute daphnia toxicity prediction was made by assessing the TS as a mixture and assessing each constituent first . Six of the seven constituents are members of the ECOSAR category "Schiff Bases-Azomethine". The seventh, benzaldehyde, the starting material for the other constituents, is a member of the ECOSAR category “Aldehydes (mono)”.

The algal growth inhibition was predicted individually for each constituent, using the respective ECOSAR category as primary categorization. The specific endpoint was the 72-hour EC50 to algae

using ‘growth rate’ as the effect. Six of the seven constituents, except benzaldehyde, were structurally very similar except for the carbon chain length and degree of unsaturation. Read-across

for all seven constituents was done using the robust read-across methodology, integral to the OECD QSAR Toolbox. The endpoint value for the TS (mixture) was then assessed both by ‘independent’ and ‘similar’ modes of action. The predicted value is a 72-hour EC50 of 29.5-30.8 mg/L to algal species. The lower value of 29.5 mg/L is accepted for this endpoint. This is a reliable prediction and satisfies the endpoint adequately.

The structures and individual data points used for read-across are included in the attached data matrix. Prediction reports for the mixture (target substance) and individual constituents are attached.

Key value for chemical safety assessment

EC50 for marine water algae:

29.5 mg/L