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|Molar mass||258.40 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Galaxolide (trade name; also known as : Abbalide, Pearlide, Astrolide, Musk 50, Polarlide.; common chemical name 1,3,4,7,8-hexahydro-4,6,6,7,8,8,-hexamethyl-cyclopenta[g[-benzopyran (HHCB) is a synthetic ingredient with a clean sweet musky floral woody odour used in fragrances. It is one of the musk components perfume and cologne manufacturers use to add a musk smell to perfume. Galaxolide was first synthesized in 1965, and used in the late 1960s in some fabric softeners & detergents. High doses were also incorporated in fine fragrances.
Galaxolide is the trade name from International Flavors & Fragrances Inc. (IFF) for the fragrance material with Chemical Abstract Service (CAS) number 1222-05-5 and CAS chemical name cyclopenta(g)-2-benzopyran, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-.
Galaxolide is also known by its IUPAC name 4,6,6,7,8,8-hexamethyl-1,3,4,6,7,8-hexahydro-cyclopenta[g]-isochromene and the more commonly used acronym of the chemical name 1,3,4,7,8-hexahydro-4,6,6,7,8,8,-hexamethyl-cyclopenta[g[-benzopyran (HHCB). The abbreviation for this chemical name, HHCB, is commonly used for Galaxolide in various publications. Galaxolide may also be known by its name under the International Nomenclature for Cosmetic Ingredients (INCI); Hexamethylindanopyran.
Galaxolide is a mixture of isomers; it has chiral centres at the 4- and 7-Carbon. The isomers are (4R,7R), (4R,7S), (4S,7S) and (4S, 7R). Galaxolide has a molecular formula of C18H26O and a molecular weight of 258.4. At room temperature it occurs as a highly viscous liquid. Melting point is -20 °C and boiling point has been reported to be 330 °C, re-calculated from a boiling point of 160 °C at 4hPa. All physical chemical data are derived from the Galaxolide REACH registration dossier.
Galaxolide was discovered at IFF in the 1960s, by Dr. Heering and Beets 
It was first synthesized in 1957 and its discovery was mainly due to the work by Beets on the osmophoric group of the polycyclic musks, where they tried to improve existing synthetic musks by making them more stable and hydrophobic 
Galaxolide has become the key synthetic musk ingredient belonging to the polycyclic musk group as defined by the International Fragrance Association (IFRA). Its odour is described as a “clean”, sweet, floral, woody musk,
Research has shown  that it is in particular the (4S, 7R) and the (4S, 7S) forms of galaxolide that are the most powerful musk notes, with odour thresholds of 1 ng/l or less.
Galaxolide has a measured Bio Concentration Factor (BCF) in fish in a range of 600 - 1600 and a log octanol/water partition coefficient (Log Kow) of around 5.5 (5.3 – 5.9).
Given the lack of bioaccumulation and toxicity the EU determined that Galaxolide does not meet the criteria for being a substance classified as Persistent, Bioaccumulative and Toxic to the environment (PBT),
Furthermore it has been shown  that Galaxolide degrades in the environment to primary degradants with log Kow <4 and further to more hydrophilic products with Log Kow of <1. Galaxolide is classified as R50/53 under the EU DSD and as H410 under EU CLP classification rules.
Although there have been reports of Galaxolide in environmental compartments, these studies have been made part of Galaxolide’s environmental safety reviews by various authorities, who have deemed that there is no need for risk reduction measures.
Although Galaxolide has been reported to be found in human bio monitoring studies its presence in human tissue has been evaluated by several scientific authorities.,
Galaxolide is not an irritant, not toxic, not a CMR substance nor a sensitizer. Despite the available test data the EU Scientific Committee for Consumer Safety did include galaxolide in their proposal for extending the allergen information on cosmetic products as it claims to have seen only up to 100 individual cases worldwide in the last several decades who have reported irritation or allergic reactions to Galaxolide through the use of cosmetic products. 
Extensive investigations into the presence of galaxolide in bio monitoring studies , have been completed and evaluated by various regulatory authorities. The outcome of all those studies, as indicated in the section on Regulatory Status below, is that Galaxolide is safe for use in consumer products.,
Regulatory and safety status
In 2002 The Scientific Committee on Cosmetics and Non-Food Products (SCCNFP; renamed recently as the Scientific Committee on Consumer Safety, or SCCS ), the expert scientific board that advises the European Commission on human health issues, reviewed the human safety of galaxolide, when used in cosmetic products, and issued a final opinion on 17 September 2002. The SCCNFP stated that “..HHCB can be safely used as a fragrance ingredient in cosmetic products without any restriction for its use.” (HHCB is an acronym for the chemical description of galaxolide.)
In March 2003, the European Chemicals Bureau (ECB) concluded that galaxolide is not a persistent, bioaccumulative and toxic substance (PBT) according to the ECB criteria and removed galaxolide from their draft list of PBTs.
Under the EU Existing Substances Directive, galaxolide is listed in the 4th Priority List of Substances for review by the EU. This Priority List was the 4th list compiled by the EU of high volume substances that were to be evaluated by the Member States’ Competent Authorities, as part of the requirements of EU Council regulation 793/93 “On the Evaluation and Control of the risk of existing substances”. The EU published the final report for this study in 2008 and concluded in this report that for all human health and environmental endpoints; “There is at present no need for further information and/or testing and no need for risk reduction measures”.
Additionally the European Union Scientific Committee for Health and Environmental Risks (SCHER), an advisory body to the European Commission, independently reviewed the environmental, human health, and indirect exposure risk assessment, and agreed with all of the conclusions from the EU experts on the outcome that “There is at present no need for further information and/or testing and no need for risk reduction measures”. The SCHER opinions for galaxolide are available for the environment, for human health and for human health though indirect exposure.
As part of the obligations under the EU’s Registration, Evaluation and Authorization of Chemicals (REACH), the producers and importers of galaxolide on the EU market have registered galaxolide in December 2010 with the European Chemicals Agency in Helsinki.
Most recently, in the USA, the Environmental Protection Agency under its Toxic Substance Control Act Work Plan Chemicals Program evaluated galaxolide for human health and environmental effects and concluded that "..the assessment does not indicate risk concerns”.
All above regulatory safety assessments reference peer reviewed publications on the presence of galaxolide in the environment and humans, and many other studies. Considering the robust safety, environmental, and exposure data on this substance, all the above reviews have concluded favorably on the safety of this fragrance ingredient.
- HHCB REACH Dossier: http://echa.europa.eu/information-on-chemicals/registered-substances, CAS 1222-05-5
- Heeringa L.G. and Beets M.G.J., 1965, New Tricyclic Isochromans with Musk Odour. United Kingdom Patent: 991,146).
- David Rowe; Chemistry and Technology of Flavours and Fragrances - 2005, p152; ISBN 1-4051-1450-9).
- G. Frater, U. Mueller & P. Kraft, Helv. Chim. Acta, 82(10), 1656-1665 (1999)
- : http://echa.europa.eu/documents/10162/947def3b-bbbf-473b-bc19-3bda7a8da910)
- OSPAR review of various musk ingredients: http://www.ospar.org/documents/dbase/publications/p00200/p00200_bd%20on%20musk%20xylene.pdf – page 39 and Annex 3
- Chen D, Zeng X, Sheng Y, Bi X, Gui H, Sheng G, Fu J. 2007. The concentrations and distribution of polycyclic musks in a typical cosmetic plant. Chemosphere. 66(2):252-8.
- Rüdel H, Böhmer W, Schröter-Kermani C. 2006. Retrospective monitoring of synthetic musk compounds in aquatic biota from German rivers and coastal areas. J Environ Monit. 8(8): 812-23
- Kannan K. Reineer JL, Yun SH. Perotta EE, Tao L, Johnson-Restrepo B, Rodan BD. 2005. Polycyclic musk compounds in higher trophic level aquatic organisms and humans from the United States. Chemosphere 61: 693–700.
- EU Scientific Committee on Health and Environmental Risks; Environmental Assessment of HHCB http://ec.europa.eu/health/ph_risk/committees/04_scher/docs/scher_o_096.pdf
- EPA review of HHCB: http://www.epa.gov/oppt/existingchemicals/pubs/HHCB%20WP%20RA%20FINAL%2008_27_14.pdf
- Ozonation: a tool for removal of pharmaceuticals, contrast media and musk fragrances from wastewater? Thomas A Ternes, Jeannette Stüber, Nadine Herrmann, Derek McDowell, Achim Ried, Martin Kampmann, and Bernhard Teiser, Water Research, April 2003, Volume 37, Issue 8, Pages 1976–1982, doi:10.1016/S0043-1354(02)00570-5
- EU Scientific Committee on Consumer Safety; Opinion on Fragrance Allergens: http://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_102.pdf, Table 7-1, page 47 and Table 13-1, page 107
- Rimkus, G.G. and M. Wolf, Polycyclic musk fragrances in human adipose tissue and human milk. Chemosphere, 1996, 33(10), pages 2033-2043, doi:10.1016/0045-6535(96)00321-9
- EU-SCCNFP safety evaluation for HHCB in cosmetics: http://ec.europa.eu/health/ph_risk/committees/sccp/documents/out179_en.pdf
- EU Risk Assessment Report on HHCB: http://echa.europa.eu/documents/10162/947def3b-bbbf-473b-bc19-3bda7a8da910
- EU-SCHER Opinion on HHCB safety for human health http://ec.europa.eu/health/ph_risk/committees/04_scher/docs/scher_o_086.pdf
- EU-SCHER Opinion on the safety of HHCB through indirect exposure: http://ec.europa.eu/health/ph_risk/committees/04_scher/docs/scher_o_094.pdf
- REACH legislation: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=oj:l:2006:396:0001:0849:en:pdf
- EPA Workplan: http://www.epa.gov/oppt/existingchemicals/pubs/workplans.html