Registration Dossier

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
0.64 mg/L
Assessment factor:
50
PNEC freshwater (intermittent releases):
1 mg/L

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
0.064 mg/L
Assessment factor:
500

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
100 mg/L
Assessment factor:
10

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
4.2 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
0.42 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
0.47 mg/kg soil dw
Extrapolation method:
equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Short-term aquatic toxicity data for the read across substance trichloro(2,4,4-trimethylpentyl)silane are available for fish; long-term data are available for invertebrates. The test organisms were primarily exposed to the hydrolysis product because the substance hydrolyses very rapidly to 2,4,4-trimethylpentylsilanetriol and hydrogen chloride. Hydrogen chloride is not harmful to aquatic organisms. Both, the registered substance and the read across substance, share the same hydrolysis product, (2,4,4-trimethylpentyl)silanetriol.  The PNECs are therefore discussed in terms of the silanol hydrolysis product, 2,4,4-trimethylpentylsilanetriol

Short-term data for algae are read-across from the substance trichloro(phenyl)silane, which hydrolyses very rapidly to phenylsilanetriol and hydrogen chloride.

The relevant values are:

 

Fish: LC50 (96-h): >100 mg/l; NOEC ≥100 mg/l

Daphnia: NOEC (21-day): 32 mg/l

Algae: EC50 (96-h): >100 mg/l; NOEC: ≥100 mg/l

 

The standard approach to PNEC calculation when long-term data are available for two trophic levels, including that which was found to be most sensitive in the short-term tests, is to apply an assessment factor of 50 to the lowest NOEC.

Therefore, PNECaquatic is 32/50 =0.64 mg/l.

Conclusion on classification

Trimethoxy(2,4,4-trimethylpentyl)silane (CAS 034396-03-7) is expected to hydrolyse rapidly (half-life approximately 5.7 hours at 20-25°C) and the silanol hydrolysis product is not readily biodegradable.

Trimethoxy(2,4,4-trimethylpentyl)silane (CAS 034396-03-7) is not classified for the environment in the EU according to Regulation (EC) No 1272/2008 because measured data for the read across substances indicate that both the parent substance and the silanol hydrolysis product are not toxic up to a concentration of 100 mg/l, i.e. lowest E(L)C50is >100 mg/l.