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EC number: 221-906-4
CAS number: 3277-26-7
No data are available for the registered
substance 1,1,3,3-tetramethyldisiloxane (CAS 3277-26-7), which
hydrolyses very rapidly to dimethylsilanol during the intermediate
hydrolysis. The substance further hydrolyses to dimethylsilanediol (CAS
1066-42-8), however the final hydrolysis rate is >48 hours, therefore as
indicated by the REACH guidance (ECHA 2016, R.16), the aquatic chemical
safety assessment and PNECs are based on the intermediate hydrolysis
product, for which short-term aquatic toxicity data have been read
across from the structural analogue trimethylsilanol (CAS 1066-40-6)
(structural analogue of dimethylsilanol).
on the short-term aquatic data set on trimethylsilanol, the most
sensitive trophic level is invertebrates, although no toxicity was
observed below 100 mg/l. For the purpose of chemical safety assessment,
a freshwater PNEC has been derived by applying an assessment factor of
1000 to the short-term data.
Short-term aquatic toxicity data are
also available on the ultimate hydrolysis product dimethylsilanediol,
where no effects were reported at the highest concentrations tested.
accordance with Column 2 of REACH Annex IX, there is no need to further
investigate the effects of this substance in a long-term aquatic
toxicity to fish study because, as indicated in guidance R.22.214.171.124 (ECHA
2016), the quantitative chemical safety assessment (conducted according
to Annex I of REACH) indicates that the Risk Characterisation Ratio is
below 1 and therefore the risk is already adequately controlled and
further testing is not justifiable.
it is concluded that the risk characterisation conclusion is
sufficiently conservative in respect of any uncertainties and therefore
further in vivo testing is not considered necessary or justified
on ethical grounds.
on how the PNEC and the risk characterisation ratio have been derived
can be found in IUCLID Section 6.0 and Chapters 9 and 10 of the Chemical
Safety Report, respectively.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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