Triethoxypropylsilane

PBT assessment

PBT assessment: overall result

Reference

Name:

Triethoxypropylsilane

Type of composition:

boundary composition of the substance

State / form:

liquid

Reference substance:

Triethoxypropylsilane

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence assessment

Triethoxy(propyl)silane (CAS 2550-02-9) hydrolyses in contact with water (t1/2 = 1.4 d at pH 7) and forms the reaction products propylsilanetriol and ethanol. According to the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (2017) hydrolysis is a primary degradation pathway and the formation of stable degradation products with PBT/vPvB properties should be considered for PBT assessment.

No data is available for the biodegradation of the target substance Triethoxy(propyl)silane (CAS 2550-02-9). Therefore, read-across to experimental data for Trimethoxy(propyl)silane (CAS 1067-25-0) was performed. Both substances share the same silanol hydrolysis product. Experimental findings for the read-across source substance Trimethoxy(propyl)silanol yielded a biodegradation of 54% in 28 d, which results in a corrected biodegradation of 4% in 28 d when the degradation of the methoxy group is accounted for. Thus, the silanol hydrolysis product is not expected to degrade and the source substance Trimethoxy(propyl)silane (CAS 1067-25-0) is not biodegradable. Based on the results of the analogue substance, the target substance Triethoxy(propyl)silane (CAS 2550-02-9) is not readily biodegradable. The other hydrolysis product, ethanol, is readily biodegradable (OECD 2004). Therefore, the target substance Triethoxy(propyl)silane (CAS 2550-02-9) is considered to meet the criteria for persistence (P and vP). 

 

Bioaccumulation assessment

The parent compound Triethoxy(propyl)silane has a measured log Kow of 3.1 and a calculated log Koa < 5. Therefore, the parent substance does not meet the screening criteria for aquatic or air breathing organisms (ECHA guidance R.11). The hydrolysis product propylsilanetriol has a predicted log Kow of -1.4. The other hydrolysis product, ethanol, has a predicted log Kow of -0.3. Thus, both hydrolysis products are also negligible with regard to bioaccumulation.

 

In conclusion, Triethoxy(propyl)silane (CAS 2550-02-9) and its hydrolysis products do not meet the criteria for bioaccumulation and are not B / vB, based on the available information.

 

Toxicity

The short-term toxicity ofTriethoxy(propyl)silane (CAS 2550-02-9)to aquatic organisms of three different trophic levels is well above 0.01 mg/L. Long-term toxicity data is available for aquatic invertebrates and algae, showing NOEC values > 0.01 mg/L. Therefore, the substance does not fulfil the environmental T criteria.

Furthermore, neither the substance nor its hydrolysis products are classified for specific target organ toxicity, carcinogenicity, or mutagenicity and are not toxic for reproduction and development towards mammals. The criteria for “T” based on mammalian effects are therefore not met.

In conclusion, the substance is not PBT/vPvB.