Trichloro(3-chloropropyl)silane

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

1.67 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

16.7 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.17 mg/L

Assessment factor:

5 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

4 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

6.5 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.65 mg/kg sediment dw

Assessment factor:

10

Extrapolation method:

equilibrium partitioning method

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.32 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Additional information

For the aquatic compartment, the PNEC of trichloro(3-chloropropyl)silane is considered entirely by read across from read-across substance (3-chloropropyltrimethoxysilane), on the basis that they share a common hydrolysis product 3-chloropropylsilanetriol. No other data are included in the discussion, although a Category approach is used to discussion of the assessment factors.

The PNEC of trichloro(3-chloropropyl)silane is considered entirely by read across from read-across substance (3-chloropropyltrimethoxysilane). Due to the very rapid hydrolysis it is appropriate to calculate PNEC_freshwateron the basis of data for the hydrolysis product, 3-chloropropylsilanetriol. The relevant values are:

Fish:LC50 (96 h): >100 mg/L

Daphnia:EC50 (48 h): 869 mg/L

Algae:EC50 (96 h): >833 mg/L

The standard approach to PNEC calculation when acute data are available for three trophic levels is to apply an assessment factor of 1000 to the lowest lethal or effect concentration (E(L)C₅₀). However, this assessment factor may be reduced by up to a factor of 10 if this is justified by the available data, for example:

• Evidence from structurally similar compounds which may demonstrate that a higher or lower factor may be appropriate.
• Knowledge of the mode of action as some substances by virtue of their structure may be known to act in a non-specific manner. A lower factor may therefore be considered. Equally a known specific mode of action may lead to a higher factor (ECHA 2009).

 

The substance is part of a category of organosilicon substances containing only hydrocarbon, halogen, alkoxy or silanol groups attached to the Si atom. The category has a low hazard profile and data are consistent with a simple polar narcosis mechanism. It is considered that the weight of evidence for the number of substances (ca.40 substances have reliable measured data) justifies a reduction of the assessment factor from the normal value of 1000. A value of 500 is used, to reflect the increased confidence in the individual values due to the low variability across the category. This is discussed further in PFA, 2010.

The lowest L(E)C50 value for3-chloropropylsilanetriolis 833 mg/l for algae. Therefore, PNEC_aquaticis 833/500 = 1.67 mg/l.

Conclusion on classification

It is proposed that trichloro(3 -chloropropyl)silane should not be classified in the EU for acute or chronic toxicity on the grounds that reliable studies for a suitable read-across substance indicate that it would not be toxic at a loading rate of 100 mg/l. The substance hydrolyses rapidly and the silanol hydrolysis product has a low log Kow.