Dichlorosilane

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Description of key information

There are no test data for the substance. However read across data for related substances gives the following results: A 72-hour EC₅₀ of >100 mg/L and a NOEC of <6.3 mg/L have been determined for the effects of related substance, trimethoxysilane (CAS 2487-90-3), on growth rate and biomass of Pseudokirchneriella subcapitata. It is likely that the test organisms were exposed to the hydrolysis products of the substance. A 72-hour EC₅₀ value of >22 mg/l and NOEC of ≥22 mg/l have been determined for the effects of the test substance on growth rate and biomass of Pseudokirchneriella subcapitata based on geometric mean measured concentrations (>100 mg/l and ≥100 mg/l respectively based on nominal concentration and >5.8 mg/l and ≥5.8 mg/l respectively based on measured final concentrations). It is likely that the test organisms were exposed to the hydrolysis products of the substance. The appropriate interpretation of these data is to use nominal concentrations, because rapid hydrolysis during test media preparation means the test organisms would have been exposed predominantly to hydrolysis products. The low recoveries based on GC analysis are due to removal of test substance by hydrolysis. The nominal results in terms of hydrolysis product are calculated by MW conversion to be an EC₅₀ value of >63 mg/L and NOEC of ≥63 mg/L.

Additional information

No test data for toxicity to aquatic algae and cyanobacteria are available for dichlorosilane. 

An algal inhibition study with dichlorosilane is considered technically unfeasible because the substance is a gas at normal temperature and pressure and is expected to react violently and rapidly with water. This violent and rapid reaction of the gas with water would render aquatic ecotoxicology testing impossible and thus testing is waived on the basis of the technical difficulty to conduct such tests.

However, algal inhibition studies are available for the related substances trimethoxysilane (CAS 2487-90-3) and tetraethyl orthosilicate (CAS 78-10-4), as supporting evidence that the silanol hydrolysis product is not toxic and adding to the weight of evidence for not carrying out any further testing.

The relevant values are:

Trimethoxysilane (CAS 2487-90-3)

A 72-h EC₅₀ value of >100 mg/l and a NOEC of <6.3 mg/l have been determined for the effects of trimethoxysilane on growth rate of Pseudokirchneriella subcapitata based on nominal concentrations.

Tetraethyl orthosilicate (CAS 78-10-4)

A 72-h EC₅₀ value of >100 mg/l and a NOEC of ≥100 mg/l have been determined for the effects of tetraethyl orthosilicate on growth rate of Pseudokirchneriella subcapitata based on nominal concentrations.