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Oxybenzone or benzophenone-3 (trade names Eusolex 4360, Escalol 567, KAHSCREEN BZ-3) is an organic compound used in sunscreens. It forms colorless crystals that are readily soluble in most organic solvents. Oxybenzone belongs to the class of aromatic ketones known as benzophenones. It provides broad-spectrum UV coverage, including UVB and short-wave UVA (ultraviolet) rays. As a photoprotective agent, it has an absorption profile spanning from 270 to 350 nm with absorption peaks at 288 and 350nm. (41) The molecule was first synthesized in 1906, but the synthesis for commercial production was not patented until 1975 (15). It was approved for use by the Food and Drug Administration (FDA) in the early 1980s and has grown to become one of the most widely used organic UVA filters in US sunscreens today. It is also found in nail polish, fragrances, hairspray, and cosmetics as a photostabilizer. Despite the photoprotection, there is much controversy surrounding oxybenzone as a toxic agent, so many countries including the US, EU, Japan, Canada, and Australia have regulated its use.

Chemical Background

Oxybenzone's ability to absorb UV rays is due to a variety of molecular interactions. In this compound, both of the phenyl rings can interact with the C=O group through inductive effects and mesomeric effects. The overlapping of the π bonds of both phenyl rings and that of the C=O creates a completely conjugated molecule as evidenced by the MO diagram. This causes the C=O group to lose part of its individual character as it integrates with the two phenyl rings. This stabilizes the system due to the transference of electron deficiency from the carbon of the carbonyl towards three of the carbons of the phenyl rings.

When examining the stability of the oxybenzone, which contributes to the absorption capabilities of the molecule, studies show that the molecule is basically locked into the conformation that places the OH group close to the C=O. Because the oxygen contains most of the electron density of the C=O bond, the electrons can interact with the hydrogen of the OH group. As a result, oxybenzone is more stable by 35.6 kJ/mol due to the presence of the intramolecular hydrogen bonding capabilities. The hydrogen bond can be classified as a "moderate" or "conventional-strong" bond, which has electrostatic character. It is this conformation that leads to oxybenzone's absorption capabilities. Research studies show that at room temperature, oxybenzone does not undergo benzophenone-like photoreduction and does not phosphoresce. At low temperatures, however, it is possible to observe both the phosphoresce and the triplet-triplet absorption spectrum. At 175K the triplet lifetime is only 24 ns. The short lifetime has been attributed to an extremely fast and reversible excited-state intramolecular hydrogen transfer between the oxygen of the C=O and the OH. This pathway provides an efficient energy-wasting pathway that is responsible for the absorption capabilities.

Production

Oxybenzone occurs naturally in some flowering plants, but is synthetically manufactured for product use in over 10 countries. (30) The US lists ozybenzone as a High Production Volume (HPV) chemical, meaning it was produced in or imported into the U.S. in >1 million pounds in 1990 and/or 1994. (15) As of March 2014, the EWG claims there are over 1200 products that contain Oxybenzone. (40)

Government positions on safety

United States

Revised as of April 1, 2013, the FDA allows Oxybenzone in cosmetic products up to 6%. (21)

European Union

The Scientific Committee on Consumer Products (SCCP) of the European Commission concluded in 2008 that it does not pose a significant risk to consumers, apart from contact allergenic potential. (18). It is allowed in cosmetics up to 10%.

Canada

Revised as of 2012, Health Canada allows Oxybenzone for cosmetic use up to 6%. (26)

Japan

Revised as of 2001, the Ministry of Health and Welfare Notification allows Oxybenzone for cosmetic use up to 5%.

Australia

Revised as of 2007, the NICNAS Cosmetic Guidelines allow Oxybenzone for cosmetic use up to 10%.

Sweden

The Swedish Research Council has determined that sunscreens with oxybenzone are unsuitable for use in young children, because children under the age of two years have not fully developed the enzymes that are believed break it down. No regulations have come of this study yet. (15)

sources

to be edited into actual references... sunscreen: a critical review (41) http://www.ewg.org/skindeep/browse.php?containing=704372&showproducts=1&notold=1 (40) http://www.cdc.gov/biomonitoring/Benzophenone-3_BiomonitoringSummary.html - (30)

http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@rn+@rel+131-57-7 (15)

http://dermalinstitute.com/us/library/66_article_Shedding_Light_on_Sun_Safety_Part_Two.html (18) http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?cfrpart=352&showfr=1 (21)

http://www.hc-sc.gc.ca/dhp-mps/consultation/natur/sunscreen-ecransolaire-eng.php (26)

http://www.mhlw.go.jp/file/06-Seisakujouhou-11120000-Iyakushokuhinkyoku/0000032704.pdf (27)