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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 (72-h): >161 mg/l growth rate and biomass Scenedesmus subspicatus Rel 2. (Read-across from CAS 78 -10 -4) 
NOEC: 110 mg/l growth rate and biomass Scenedesmus subspicatus Rel 2. (Read-across from CAS 78 -10 -4)
EC50 (72-h): >22 mg/l growth rate and biomass Pseudokirchnerella subcapitata Rel 2. (Read-across from CAS 18765-38-3)
NOEC: ≥22 mg/l growth rate and biomass Pseudokirchnerella subcapitata Rel 2. (Read-across from CAS 18765-38-3)
NOEC (48 h): 1150 mg/l mortality Chlorella pyrenoidosa (from EU Risk Assessment for Propanol)

Key value for chemical safety assessment

Additional information

There are no short-term data for toxicity of the registered substance to aquatic algae and cyanobacteria. However data are available for two structurally-analogous read-across substances; tetrakis(2-butoxyethyl) orthosilicate (CAS 18765 -38 -3) and tetraethyl orthosilicate (CAS 78 -10 -4).

·        A 72-hour EC50 value of >161 mg/l and a NOEC of approximately 110 mg/l have been determined for the effects of tetrakis(2 -butoxyethyl) orthosilicate on growth rate and biomass of Scenedesmus subspicatus based on initial measured concentration.

·        A 72-hour EC50 value of >22 mg/l and NOEC of ≥22 mg/l have been determined for the effects of tetraethyl orthosilicate on growth rate and biomass of Pseudokirchnerella subcapitata based on geometric mean measured concentrations (>100 mg/L and ≥100 mg/l respectively based on nominal concentration). 

Both of these substances hydrolyse in water and it is therefore likely that the test organisms were primarily exposed to their hydrolysis products.

The studies were conducted according to an appropriate OECD test guideline, in compliance with GLP and were considered to be reliability 1 (reliable without restrictions). Read across to the registered substance is considered scientifically justified; the read across is considered to be reliability 2. Further information on read-across is given in the Aquatic toxicity endpoint summary.

However, in view of the rapid hydrolysis of the registered substance to silicic acid and propanol and the absence of toxicicity to aquatic organisms of silicic acid, the PNECaquatic(freshwater)will be based on data for propanol.