Synthetic amorphous silica is an inorganic substance that is poorly soluble in water. Owing to this property, its bioavailability for water organisms is very low. In acute tests conducted in accordance with OECD testing guidelines, no harmful effect was established either on fish or on water fleas (Daphnia), given starting concentrations of 1,000 and 10,000 mg/l.
Owing to the physical and chemical properties of the substance and its acute eco-toxicity data, neither a chronic impact nor accumulation in water organisms can be expected.

The generally applicable regulations for determining the biodegradability of substances (OECD and EC guidelines) only apply to organic substances. Synthetic amorphous silica is an inert inorganic substance and is not biodegraded by microorganisms.

The German Commission for the Evaluation of Substances Hazardous to Water (KBwS) has classified synthetic amorphous silica as not hazardous to water (KBwS No. 849). Silicon dioxide has also been included in the OSPAR List of Substances/Preparations Used and Discharged Offshore which Are Considered to Pose Little or No Risk to the Environment (PLONOR).