Dichlorocyclohexylmethylsilane

Endpoint summary

Additional information

There are no reliable aquatic toxicity data available for dichloro(cyclohexyl)methylsilane (CAS 5578-42-7), therefore good quality data for the structurally-related substance, cyclohexyl(dimethoxy)methylsilane (CAS 17865-32-6), have been read across.

 

Reliable short-term toxicity tests results are available for freshwater fish (Oncorhynchus mykiss), invertebrates (Daphnia magna) and algae (Desmodesmus subspicatus) for cyclohexyl(dimethoxy)methylsilane (CAS 17865-32-6). The relevant short-term values are:

 

Fish: LC₅₀ (96 h): 50 mg/l based on nominal test substance concentrations. The LC₅₀ value based on geometric mean measured concentrations of the parent substance is 35 mg/l. However, the fish were likely to have been exposed to a mixture of parent test substance and hydrolysis products. Because the relevant assessment entity is the silanol hydrolysis product cyclohexyl(methyl)silanediol, the nominal test substance concentration is used for chemical safety assessment with a molecular weight correction to reflect the concentration of cyclohexyl(methyl)silanediol. The relevant short-term toxicity to fish value, expressed in terms of concentration of the silanol hydrolysis product cyclohexyl(methyl)silanediol, is therefore 43 mg/l.

 

Daphnia: EC₅₀ (48 h): 24 mg/l based on nominal test substance concentrations. The EC₅₀ value based on geometric mean measured concentrations of the parent substance is 13 mg/l. However, the Daphnia were likely to have been exposed to a mixture of parent test substance and hydrolysis products, with the hydrolysis products predominating towards the end of the test. Because the relevant assessment entity is the silanol hydrolysis product cyclohexyl(methyl)silanediol, the nominal test substance concentration is used for chemical safety assessment with a molecular weight correction to reflect the concentration of cyclohexyl(methyl)silanediol. The relevant short-term toxicity to invertebrates value, expressed in terms of concentration of the silanol hydrolysis product cyclohexyl(methyl)silanediol, is therefore 20 mg/l.

 

Algae: EC₅₀ (72 h): 35 mg/l; NOEC: 12.5 mg/l expressed in terms of nominal concentrations of test substance. However, exposure is likely to be a mixture of parent test substance and hydrolysis products, with the hydrolysis products predominating towards the end of the test. Because the relevant assessment entity is the silanol hydrolysis product cyclohexyl(methyl)silanediol, the nominal test substance concentration is used for chemical safety assessment with a molecular weight correction to reflect the concentration of cyclohexyl(methyl)silanediol. The relevant toxicity to algae values, expressed in terms of concentration of the silanol hydrolysis product cyclohexyl(methyl)silanediol, are therefore EC₅₀ 30 mg/l and NOEC 11 mg/l.

 

No toxicity to microorganisms data are available for dichloro(cyclohexyl)methylsilane. Data from an activated sludge respiration inhibition test for the structurally-related substance, dicyclopentyldichlorosilane (CAS 139147-73-2), have been read-across. An EC₅₀value of >100mg/l was determined.

 

Data for the test substance dichloro(cyclohexyl)methylsilane (CAS 5578-42-7)

A 48-h EL₅₀ value of 26 mg/l has been determined for the effects of the registered substance on mobility of Daphnia magna based on nominal test substance loading rate. The results of the study are considered to be uncertain due to the measured DOC (dissolved organic carbon) concentrations being 30% of nominal and this being attributable to the formation of insoluble polymers. The formation of polymers would not take place at the concentrations predicted in the environment (see Section 9 of the CSR) and the study is considered to be reliability 4 due to the uncertainty of the form of the substance the organisms were exposed to.