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Diss Factsheets

Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

Short-term toxicity to invertebrates: 48 hr EC50 6.49 mg/l (nominal, tert-butyldimethylsilanol) (OECD TG 202).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
6.49 mg/L

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 hydolysis 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 aquatic invertebrates, has been based on the properties of the silanol hydrolysis product tert-butyldimethylsilanol (CAS No. 18173-64-3).

A 48-h EC50 value of 6.49 mg/l (nominal) has been determined for the effects of tert-butyldimethylsilanol (CAS No. 18173-64-3) on the mobility of Daphnia magna. The nominal test concentrations are supported by GC analysis. The measured concentrations ranged between 94.6 -102% 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 shows some toxicity to invertebrates, but is less toxic than the silanol hydrolysis product tert-butyldimethylsilanol.


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).