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EC number: 223-620-5
CAS number: 3982-82-9
-Tetramethyl-1,1,5,5-tetraphenyltrisiloxane (CAS 3982-82-9) has
an extremely low estimated water solubility (5.9E-09 mg/l (insoluble))
and very high estimated log Kow (9.0 at 20°C).
The substance is susceptible to hydrolysis with a predicted half-life of
>329 hours at pH 7 and 20°C. The reaction products are
methyl(diphenyl)silanol (CAS 778-25-6) and dimethylsilanediol (CAS
1066-42-8). The registration substance has a high adsorption potential,
and once adsorbed, hydrolysis may not occur.
On the basis that the substance is insoluble, data waivers are in place
for short-term toxicity to aquatic invertebrates and algae. The
physicochemical properties of the registration substance indicate that
maintaining stable aqueous test solutions will be extremely difficult.
Furthermore, the substance will have the tendency to adsorb onto the
glassware under experimental conditions. This contributes to technical
difficulties making reliable experimental studies very difficult to
- Above a log Kow of 6.0 short-term toxicity effects are not
expected to occur, because the very limited aqueous solubility prevents
toxic concentrations being achieved in exposure media. Similarly, above
log Kow of 8, long-term toxicity effects are not expected.1
- Regarding environmental exposure: the chemical properties indicate the
substance will have the tendency to adsorb onto dissolved organic matter
in the natural environment. Therefore, aqueous exposure is unlikely.
- The physicochemical properties and very high expected Koc value
means that if the substance were to enter a wastewater treatment plant
in influent waste waters, it would partition mainly to sludges (a small
proportion may be volatilised), with a negligible amount passing to
water. The result is that exposure of freshwater or marine aquatic
compartments is negligible.
high log Kow (9.0) and very low limit of solubility in water
mean the substance has very low bioavailability. For substances with
these properties, chronic aquatic ecotoxicity is unlikely to be of
concern. The principle of log Kow-based cut-off values for
toxic effects has been embraced by the ICCA and OECD high Production
Volume (HPV) chemical programmes (e.g. UNEP, 2000). The US EPA has also
accepted them in its Pollution Prevention Framework
(http://www.epa.gov/oppt/p2framework/docs/casestu.htm). The ECOSAR QSAR
applies a log Kow cut-off value of 8.0 beyond which chronic
toxicity of neutral organics would not be expected because of
limitations in bioavailability and uptake of the substance (Clements,
1996). These cut-offs are empirically derived and based on experimental
Consideration of low functionality side chains and reactive groups
Phenyl group: The ecotoxicity of phenyls is related to non-polar
narcosis. The ecotoxicity of substances with phenyl groups increases
with increasing log Kow. For example, trichlorophenylsilane
(CAS 98-13-5) has a very fast hydrolysis rate and the log Kow of
the hydrolysis product is -0.2. Short-term toxicity data with
trichlorophenylsilane determine no effects up to 100 mg/l (Springborn
Smithers 2009a, b and c).
Clements (1996). Estimating toxicity of industrial chemicals to aquatic
organisms using structure-activity relationships. Edited by: Richard G.
Clements. Contributors: R.G. Clements, J.V. Nabholz, M. Zeeman,
Environmental Effects Branch, Health and Environmental Review Division,
Office of Pollution Prevention and Toxics, U.S. Environmental Protection
Agency, Washington, DC 20460, August 30, 1996.
UNEP (2000). OECD SIDS Alfa Olefins (CAS N°:592-41-6, 111-66-0,
872-05-9,112-41-4, 1120-36-1). UNEP Publications.
The substance has no reliable ecotoxicity data: testing is waived
due to the insolubility of the test substance meaning it is technically
not feasible to perform the studies and toxic effects are not likely to
be expressed at the limit of solubility.
It is therefore proposed that
3982-82-9) should not be classified in the EU for acute or
According to Regulation (EC) No 1272/2008 (CLP):
Aquatic Acute: Not classified
Aquatic Chronic: Not Classified
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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