Hazardous Substances Series ------------------------------------------------------------------------------------------------------------------------------------------- Hexamethyldisiloxane (HMDS)1 OSPAR Commission 2004 1 OSPAR 2007 agreed to deselect Hexamethyldisiloxane (HMDS) from the List of Chemicals for Priority Action (OSPAR 07/24/1, §8.3). OSPAR Commission, 2004: OSPAR background document on hexamethyldisiloxane ____________________________________________________________________________________________ The Convention for the Protection of the Marine Environment of the North-East Atlantic (the “OSPAR Convention”) was opened for signature at the Ministerial Meeting of the former Oslo and Paris Commissions in Paris on 22 September 1992, The Convention entered into force on 25 March 1998. It has been ratified by Belgium, Denmark, Finland, France, Germany, Iceland, Ireland, Luxembourg, Netherlands, Norway, Portugal, Sweden, Switzerland and the United Kingdom and approved by the European Community and Spain. La Convention pour la protection du milieu marin de l'Atlantique du Nord-Est, dite Convention OSPAR, a été ouverte à la signature à la réunion ministérielle des anciennes Commissions d'Oslo et de Paris, à Paris le 22 septembre 1992. La Convention est entrée en vigueur le 25 mars 1998. La Convention a été ratifiée par l'Allemagne, la Belgique, le Danemark, la Finlande, la France, l’Irlande, l’Islande, le Luxembourg, la Norvège, les Pays-Bas, le Portugal, le Royaume-Uni de Grande Bretagne et d’Irlande du Nord, la Suède et la Suisse et approuvée par la Communauté européenne et l’Espagne. © OSPAR Commission, 2004. Permission may be granted by the publishers for the report to be wholly or partly reproduced in publications provided that the source of the extract is clearly indicated. © Commission OSPAR, 2004. La reproduction de tout ou partie de ce rapport dans une publication peut être autorisée par l’Editeur, sous réserve que l’origine de l’extrait soit clairement mentionnée. ISBN 1-904426-41-7 2 OSPAR Commission, 2004: OSPAR background document on hexamethyldisiloxane _______________________________________________________________________________________________ Contents Executive summary ........................................................................................................................................... 5 Récapitulatif....................................................................................................................................................... 6 I. Environmental properties.......................................................................................................................... 7 I.1. General substance information (physico-chemical properties) .................................................... 7 I.1.1. Melting point .................................................................................................................. 7 I.1.2. Boiling point ................................................................................................................... 7 I.1.3. Vapour pressure ............................................................................................................ 7 I.1.4. Solubility ........................................................................................................................ 7 I.1.5. Partition coefficient ........................................................................................................ 8 I.1.6. Summary ....................................................................................................................... 9 I.2. Degradation................................................................................................................................... 9 I.2.1. Abiotic degradation........................................................................................................ 9 I.2.2. Biodegradation ............................................................................................................ 10 I.3. Bioaccumulation.......................................................................................................................... 10 I.4. Aquatic toxicity ............................................................................................................................ 10 I.4.1. Water organisms ......................................................................................................... 10 I.4.2. Sediment-dwelling organisms ..................................................................................... 12 I.4.3. Terrestrial compartment .............................................................................................. 12 I.4.4. Ecotoxicity to micro-organisms.................................................................................... 12 I.4.5. Summary ..................................................................................................................... 12 I.5. Toxicological properties .............................................................................................................. 12 I.5.1. Reproduction studies................................................................................................... 12 I.5.2. Mutagenicity studies .................................................................................................... 13 I.5.3. Carcinogenic potential................................................................................................. 13 I.6. PBT assessment......................................................................................................................... 13 II. Information on sources of HMDS (production and uses) ....................................................................... 13 II.1. Production and import................................................................................................................. 16 II.2. Generation of HMDS from other silicon-containing substances................................................. 16 II.3. Reprocessing of HMDS by-product to hexamethyldisilazane, trimethylsilylurea and trimethylchlorosilane (trimethylsilylchloride – TMCS) ................................................................. 17 II.4. Uses of HMDS ............................................................................................................................ 18 II.5. Overall mass balance ................................................................................................................. 18 III. Concentrations in the environment......................................................................................................... 18 III.1. Exposure assessment................................................................................................................... 18 III.1.1. Release from production ............................................................................................. 18 III.1.2. Release from the generation of HMDS from other silicon-containing substances...... 18 III.1.3. Release from reprocessing of HMDS by-product........................................................ 19 III.1.4. Release from uses....................................................................................................... 19 III.2. Aquatic compartment .................................................................................................................. 19 III.2.1. Inland environment ...................................................................................................... 19 III.2.2. Marine environment..................................................................................................... 21 III.2.3. Terrestrial compartment .............................................................................................. 22 III.2.4. Atmosphere ................................................................................................................. 22 III.2.5. Secondary poisoning................................................................................................... 22 IV. Effects assessment................................................................................................................................. 23 IV.1. Aquatic compartment .................................................................................................................. 23 IV.1.1. Water column............................................................................................................... 23 IV.1.2. Sediment...................................................................................................................... 23 3 OSPAR Commission, 2004: OSPAR background document on hexamethyldisiloxane _______________________________________________________________________________________________ IV.2. Terrestrial compartment.............................................................................................................. 24 IV.3. Atmosphere................................................................................................................................. 24 IV.4. Secondary poisoning .................................................................................................................. 24 IV.4.1. Oral toxicity.................................................................................................................. 24 IV.4.2. PNEC for secondary poisoning ................................................................................... 25 V. Risk assessment....................................................................................................................................