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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Short-term toxicity to algae: 72 hour ErC50 >118 mg/l and NOEC 118 mg/l (highest concentration tested) (OECD 201), read-across from the silanol hydrolysis product of the registration substance, dimethylsilanediol (CAS 1066-42-8).

Key value for chemical safety assessment

EC50 for freshwater algae:
118 mg/L

Additional information

2,2,4,4,6,6-Hexamethylcyclotrisilazane hydrolyses very rapidly in water to give dimethylsilanediol and ammonia/ammonium ions.

There are no reliable algal inhibition data available for 2,2,4,4,6,6-hexamethylcyclotrisilazane (CAS 1009-93-4), therefore good quality data for its silanol hydrolysis product, dimethylsilanediol (CAS 1066-42-8) have been read across. The other hydrolysis product of the registration substance is ammonia/ammonium ions.

A 72 hour ErC50 value of >118 mg/l and NOEC of 118 mg/l (highest concentration tested) have been determined for the effects of dimethylsilanediol (CAS 1066-42-8) on growth rate and biomass of Pseudokirchneriella subcapitata.

Refer to the discussion in the Section 6 endpoint summary for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.

Reliable short-term test results are available for ammonia sourced from the Environment Agency Proposed EQS for Water Framework Directive Annex VIII Substances: Ammonia (un-ionized) 2007. A five day EC50 of 2.0 mg NH3/L, and a 14 day LOEC of 3.0 mg NH3/L has been reported for toxicity of ammonia to algae.