Isobutylisopropyldimethoxysilane

Endpoint summary

Additional information

The test substance is a liquid under all environmental conditions and is slightly solubility in water (18 mg/L) and is of low volatility (based on vapour pressure of 303.8 Pa at 25 °C).  The substance was determined to have a log Koc value of 2.49 by HPLC using soil adsorption reference data, indicating a moderate affinity for soil. As such, any environmental release will result in the majority of the substance compartmentalising into the soil..

A Level III fugacity model was conducted in the US EPA EPISUITE, which assumes steady-state but not equilibrium conditions. The Level III model in EPI Suite predicts partitioning between air, soil, sediment and water using a combination of default parameters and various input parameters. This model has been used to calculate the theoretical distribution of the substance between four environmental compartments (air, water, soil, sediment) at steady state in a unit world. The results obtained from modelling are as follows:

Air: 4.98%

Water: 17.9%

Soil: 75.5%

Sediment: 1.63%

It is proposed that the majority of the substance is modelled to distribute to the soil compartment within the constraints of the QSAR model. 

The substance achieved 0% biodegradation in a 28-day CO2 evolution ready biodegradation study therefore it is not readily biodegradable. This indicates that the substance is unlikely to achieve a half-life of less than 40 or 60 days within fresh water attributed to ready biodegradation alone. The substance undergoes hydrolysis at environmentally relevant pH values (half-life of 45.9 hours at pH 7 and of 27.1 hours at pH 9 and at 25°C). Studies on direct phototransformation in water are not available, but it is assumed on the basis of chemical structure and nature of use that the substance is not degraded by direct photolysis. It is concluded, therefore, that hydrolysis will contribute to the depletion of the substance within the environment therefore the substance is not considered to be persistent.

The substance has been determined to have a high partition coefficient value (log Kow = 5.1 at 25°C), which demonstrates a potential to bioaccumulate, however, a BCF value of 1076 L/kg was obtained for the substance using a valid QSAR model therefore the substance is not considered to be bioaccumulative on the basis of the QSAR data developed. The same QSAR model was used to predict the QSAR value for the predicted main hydrolysis product of CAS 111439-76-0. A BCF value of 8.346 L/kg was obtained for the predicted hydrolysis product therefore the hydrolysis product is not considered to be bioaccumulative. As the substance is not anticipated to bioaccumulate, effects due to secondary poisoning are unlikely in the event of exposure to higher level organisms via ingestion of environmental organisms.