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Short-term toxicity to fish

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Description of key information

Short-term toxicity to fish: 96 hr LC50 > 100mg/l (nominal, tert-butyldimethylsilanol) (OECD TG 203).

Key value for chemical safety assessment

Additional information

The registered substance, 1-(tert-butyldimethylsilyl)piperazine (CAS No. 138938-64-4) hydrolyses very rapidly in contact with water to form tert-butyldimethylsilanol (CAS No. 18173-64-3) and piperazine. As per the REACH guidance (ECHA 2016, R.7b) which states that "when the hydrolysis half-life is less than 12 hours, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity", the aquatic toxicity assessment including fish, has been based on the properties of the silanol hydrolysis product, tert-butyldimethylsilanol (CAS No. 18173-64-3).

A 96-h LC50 value of >100 mg/l (nominal) (highest concentration tested) has been determined for the effects of tert-butyldimethylsilanol (CAS No. 18173-64-3) on the mortality of Medaka fish. The nominal test concentrations are supported by GC analysis. The measured concentrations ranged between 87.7-104% of the nominal.

The registrant does not hold data for the non-silanol hydrolysis product, piperazine (CAS No. 110-85-0). However, aquatic data are reported in the SIAR (SIDS INITIAL ASSESSMENT PROFILE for Piperazine, CAS 110-85-0, SIAM 18, 20-23 April 2004) which show that piperazine is not toxic to fish in short-term tests.


ECHA (2016). European Chemicals Agency. Guidance on information requirements and Chemical Safety Assessment. Chapter R.16: Environmental exposure assessment. Version: 3.0, February 2016 (Section R. Degradation in the environment).