3-(triethoxysilyl)propyl methacrylate

Endpoint summary

Additional information

Reliable short-term toxicity to Daphnia and algae experimental data are available with the registration substance. The studies were designed to focus on the parent substance. The relevant values are:

Daphnia: 48 h EC₅₀: >75.3 mg/l (parent substance)

Algae: 72 h ErC₅₀: 36.2 mg/l, ErC₁₀: 9.39 mg/l (parent substance)

The substance undergoes hydrolysis at a moderate rate under neutral conditions, with faster reaction rates at higher or lower pHs. Due to the semi-static design of the Daphnia immobilisation test, and neutralisation of pH, exposure concentrations of the parent substance were adequately maintained in test media to allow a meaningful test of the effects of the parent substance. However, due to the static regime of the algal test, and the fact that the growth of algae can increase test media pH, degradation by hydrolysis could have been more extensive.

In addition, for the parent substance, aquatic effects have been predicted using reliable, freely-available QSAR software.

The relevant estimated short-term values for the registered substance are:

Daphnia: EC₅₀ (48 h): 6.2 mg/l (ECOSAR v2.0, methacrylates algorithm)

Algae: EC₅₀ (96 h): 4.1 mg/l (ECOSAR v2.0, methacrylates algorithm)

In the case of Daphnia and algae, further testing has now demonstrated that the QSARs may have been too conservative, because the experimental results gave higher E(L)C₅₀ values. However, the methacrylate functional group is a structural alert for fish meaning that a specific mode of action is theoretically possible, therefore some caution is appropriate for this endpoint.

In view of the hydrolysis half-life, partial abiotic degradation within the wastewater treatment plant and in receiving waters is to be expected, particularly where the pH is higher or lower than pH7 within the normal environmental pH range. This means that soil and sediments, and to an extent also fresh and marine waters, may also be exposed partially or predominantly to the hydrolysis products. Therefore the aquatic toxicity for the hydrolysis products has also been considered. The effects assessment for the silanol hydrolysis product is based on existing studies with an analogous alkoxysilane, which hydrolyses rapidly generating the same hydrolysis product. The other hydrolysis product, ethanol, is not significantly toxic to aquatic organisms in published studies and is not considered further.

The relevant estimated short-term values for the silanol hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, are as follows (based on studies conducted with the analogous substance 3-trimethoxysilylpropyl methacrylate (CAS 2530-85-0); results re-calculated with molecular weight adjustment and expressed as concentration of 3-(trihydroxysilyl)propyl methacrylate) are:

Daphnia: EC₅₀ (48 h): >83 mg/ l and >727 mg/l; NOEC: ≥83 mg/l and ≥727 mg/l

Algae: EC₅₀ (72 h): >83 mg/l and >445 mg/l; NOEC: ≥83 mg/l and 267 mg/l