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Classification & Labelling & PBT assessment

PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

Persistence Assessment

Trichloro(4-methylphenyl)silane (CAS 701-35-9) is expected to hydrolyse rapidly in contact with water (estimated half-life < 1 min at pH 4-9 and 1.5 °C) to (4-methylphenyl)silanetriol and hydrochloric acid. According to the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (2017), hydrolysis is considered as primary degradation, and the formation of stable degradation products with PBT/vPvB properties should be considered for PBT assessment.

 

One study is available, in which the biodegradation potential of the analogue substance trichloro(phenyl)silane (CAS 98-13-5) was tested (OECD guideline 310 and GLP). The substance reached a biodegradation value of 1% after 28 d and 0% after 60 d. Therefore, the target substance is not considered as readily biodegradable and the P (vP) criterion is met.

 

Bioaccumulation Assessment

Trichloro(4-methylphenyl)silane (CAS 701-35-9) hydrolyses rapidly into (4-methylphenyl)silanetriol and hydrochloric acid (half-life < 1 min at pH 4-9 and 1.5 °C). The hydrolysis products have a very low bioaccumulation potential. The silanol hydrolysis product bears a log Pow of -0.6 and BCF values between 0.91 and 3.16 L/Kg (QSAR), showing that bioaccumulation is not expected. Therefore according to ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (2017) the substance is not B or vB.

 

Toxicity Assessment

Studies with aquatic organisms of three different trophic levels with an appropriate analogue substance did not show any adverse short term toxicity effects up to the highest tested concentration of 100 mg/L. Long-term toxicity data available for algae, showed that the substance and its hydrolysis products exhibit EC10/NOEC > 0.01 mg/L and are therefore not considered as T for the environment.

Furthermore, the substance is not classified for specific target organ toxicity, carcinogenicity, mutagenicity and is not toxic for reproduction and development towards mammals. The criteria for “T” based on mammalian effects are therefore not met.