Registration Dossier

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
0.9 mg/L
Assessment factor:
10
Extrapolation method:
assessment factor

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
0.9 mg/L
Assessment factor:
10
Extrapolation method:
assessment factor

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
51 mg/L
Assessment factor:
10
Extrapolation method:
assessment factor

Hazard for air

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
11 mg/kg soil dw
Assessment factor:
10

Hazard for predators

Additional information

Short term toxicity tests have been performed on disodium hexafluorosilicate. Toxicity to fish, algae and microorganism has been determined. However, there are no available data on long term toxicity to the aquatic environment, which are preferred to derive PNECs. Due to the presence of hydrolysable groups on its chemical structure, fluorosilicate anions are not expected to remain in solution long under environmental conditions. Instead, fluoride anions will be formed. Thus, the performance of such tests is unjustified, since there are reliable studies on sodium fluoride or hydrogen fluoride. Read-across to sodium fluoride is appropriate. Thus, PNECs will be derived based on long term studies on NaF.

Conclusion on classification

Aquatic toxicity values experimentally obtained for disodium hexafluorosilicate are the following: 96h EC50 (fish)= 37.5 mg/l 48h EC50 (daphnia)= 35.4 mg/l 72h ErC50 (alga)= 18 mg/l. The three of them are between 10 and 100 mg/l.

The substance readily dissociates in water and undergoes further hydrolysis is hydrolisable at environmental conditions, providing fluoride. Thus, the substance is unstable in water and therefore rapidly degradable. Moreover, as its bioaccumulation potential cannot be assessed, it is then justified to use biodegradation and bioaccumulation results on fluorides for assessment.

As indicated in endpoint 5.3.1, BCF for fluorides is lower than the threshold of 2000, meaning that the substance is considered not bioaccumulative.

Considering all data together, disodium hexafluorosilicate shall not be classified for aquatic toxicity.