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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Toxicity to algae: 72 hr EC50 84.0 mg/l and NOEC 12.5 mg/l (nominal, tert-butyldimethylsilanol) (OECD TG 201).

Key value for chemical safety assessment

EC50 for freshwater algae:
84 mg/L
EC10 or NOEC for freshwater algae:
12.5 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 2016c, 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 aquatic invertebrates, has been based on the properties of the silanol hydrolysis product tert-butyldimethylsilanol (CAS No. 18173-64-3).

A 72-h EC50 value of 84.0 mg/l and NOEC of 12.5 mg/l (nominal) have been determined for the effects of tert-butyldimethylsilanol (CAS No. 18173-64-3) on growth rate of Pseudokirchneriella subcapitata. The nominal test concentrations are supported by GC analysis. The measured concentrations ranged between 85.6 -96.4% 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 algae.


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).