1,1,1,3,5,5,5-heptamethyltrisiloxane

Endpoint summary

Additional information

Reliable short-term toxicity tests results are available for freshwater fish (Brachydanio rerio), invertebrates (Daphnia magna) and algae (Pseudokirchneriella subcapitata) for 1,1,1,3,5,5,5-heptamethyltrisiloxane (CAS 1873-88-7). The relevant short-term values are:

• A 96-hour LC₅₀ value of >0.108 mg/l has been determined for the effects of the test substance on mortality of Brachydanio rerio (new name Danio rerio) based on geometric mean measured concentrations (Harlan, 2011b).
• A 48-hour EC₅₀ value of >0.030 mg/l has been determined for the effects of the test substance on mobility of Daphnia magna based on geometric mean measured concentrations (Harlan, 2011c).
• A 72-hour EC₅₀ value of >0.019 mg/l and NOEC of ≥0.019 mg/l have been determined for the effects of the test substance on growth rate and yield of Pseudokirchneriella subcapitata based on geometric mean measured concentrations (Harlan, 2011d).

The water solubility limit of the test substance has been determined in a separate study to be 0.02 mg/l.

There are no long-term data for the registered substance. However, the following data are available for the structurally-analogous read-across substance octamethyltrisiloxane (CAS: 107-51-7):

• A 90-day NOEC of ≥0.027 mg/l (time-weighted mean measured concentration) has been determined for effects on embryo survival, larval hatch and growth (length and dry weight) in an early life-stage test with Oncorhynchus mykiss (Smithers Viscient, 2010).
• A 21-day EC₅₀ value of >0.015 mg/l (arithmetic mean measured concentration) has been determined for effects on survival and mobility of Daphnia magna and a NOEC of ≥0.015 mg/l has been determined for effects on growth and reproduction (Wildlife International, 2010).

There are no reliable data available for toxicity to microorganisms.

A 3 hour EC₅₀ value of >100 mg/l (ASRI) is read-across from the structurally-related substance L4 (CAS 141-62-8) (Desmares-Koopmans, 2010).

Trimethoxysilane (CAS 2487-90-3) is used to support short-term toxicity to fish, aquatic invertebrates and algae endpoints, because it has an Si-H bond that will undergo the same reaction as the registration substance. E(L)C₅₀ values of >100 mg/l for each species have been determined. Read-across from trimethoxysilane is not used to fulfil any data-gap, but is used to demonstrate that presence of the Si-H bond does not cause toxic effects.